bs_bs_banner Botanical Journal of the Linnean Society, 2014, 176, 260–276. With 6 figures Structure and evolution of the pod in Indigofera (Fabaceae) reveals a trend towards small thin indehiscent pods Downloaded from https://academic.oup.com/botlinnean/article-abstract/176/2/260/2416440 by guest on 15 June 2020 VIBHA CHAUHAN and ARUN K. PANDEY* Department of Botany, University of Delhi, Delhi-110007, India Received 9 July 2013; revised 8 April 2014; accepted for publication 27 July 2014 Pod morphology and anatomy have been studied in 28 species and four varieties of Indian Indigofera. Pods of Indigofera spp. differ with respect to size, the relative thickness of the fruit wall, the number of sclerenchymatous layers in the endocarp, the presence/absence of hypodermis and trichomes, and the presence of separation tissue. Anatomically, the pericarp is broadly characterized into three types: type I (thin pericarp and three to five sclerenchymatous layers in the endocarp), type II (intermediary pericarp thickness and six to eight sclerenchyma- tous layers), and type III (thick pericarp and more than eight sclerenchymatous layers). The distribution of these types across the tribe is not congruent with the current phylogenetic analyses. Type III pericarp (present in the early diverging lineages of the tribe) represents the most primitive state, whereas type I and type II pericarps are derived. Fruits of Indigofera generally show normal explosive dehiscence as a means of dispersal of seeds, although some species show adaptations for dispersal by wind. In Indigofera, dehiscence is caused by a separation layer present at the dorsal and ventral sutures except in some species (Indigofera hochstetteri, Indigofera karnatakana, Indigofera glandulosa var. sykesii, and Indigofera trita var. scabra) in which no separation tissue is present; these species show delayed dehiscence or an indehiscent condition. The indehiscent pod type is considered to be apomorphic. The taxonomic, functional, and evolutionary significance of morphological and anatomical features in fruits of the genus Indigofera has been evaluated. © 2014 The Linnean Society of London, Botanical Journal of the Linnean Society, 2014, 176, 260–276. ADDITIONAL KEYWORDS: anatomy – dehiscence – Leguminosae – morphology. INTRODUCTION and erect herbs to under-shrubs, robust shrubs, and rarely trees (Fig. 1). Indigofera L. (tribe Indigofereae, Fabaceae) includes Fruit morphology, anatomy, and dehiscence mecha- 700–750 species (Schrire, 2005; Schrire et al., 2009). nisms in Fabaceae have been investigated in various The genus is pantropical in distribution but the major studies (Fahn & Zohary, 1955; Esau, 1962; Fahn, centres of diversity are in Africa and Madagascar (550 1967, 1982; Pate & Kuo, 1981; Kirkbride, Gunn & species), the Sino-Himalayan region (105 species), Weitzman, 2003). In Fabaceae, the pericarp consists and Australia (50 species); the remaining 45 species of an exocarp (single or biseriate epidermal cell occur in the New World (Schrire et al., 2009). In India, layers), mesocarp (multiple parenchyma and collen- the genus is represented by 60 species and 11 varie- chymas cell layers), and endocarp (variable number of ties, of which 16 species and seven varieties are sclerenchyma cell layers). The mid region of the meso- endemic (Schrire, 1992; Sanjappa, 1995; Chauhan, carp is traversed by vascular strands. The endocarp is Pandey & Schaefer, 2013). Indigofera spp. are septate between seeds and often shows tannin spots. annuals or perennials and habit varies from prostrate Usually, there is a relationship between the histologi- cal structure of the pericarp and the manner of fruit *Corresponding author. E-mail: arunkpandey@botany.du.ac.in; and seed dispersal (Guttenberg, 1971; Fahn & arunkpandey@hotmail.com Werker, 1972). When the fruit matures, the two 260 © 2014 The Linnean Society of London, Botanical Journal of the Linnean Society, 2014, 176, 260–276  POD STRUCTURE AND EVOLUTION IN INDIGOFERA 261 Downloaded from https://academic.oup.com/botlinnean/article-abstract/176/2/260/2416440 by guest on 15 June 2020 Figure 1. Indigofera species showing habit, leaf types, flower and fruit. A, Indigofera oblongifolia. B, Indigofera trifoliata. C, Indigofera astragalina. D, Indigofera cassioides. E, Indigofera aspalathoides. F, Indigofera hendecaphylla. G, Indigofera dalzellii. valves of the dried legume usually twist. Dehiscence The mechanism of dehiscence and the function of is brought about by the uneven shrinkage of the separation tissue in the endocarp in the process of thickened walls of the pericarp cells. The greatest dehiscence were described by Fahn & Zohary (1955). shrinkage occurs at right angles to the longitudinal Buckovic (1952) studied the anatomy of the legume pod axis of the fruit and microfibrils. The cell wall of the and proposed that pod dehiscence was caused by mature fruit dries and shrinks causing explosive different rates of moisture loss in different tissues, dehiscence (Fahn & Zohary, 1955; Fahn, 1982). with the rate of loss being much higher in the paren- © 2014 The Linnean Society of London, Botanical Journal of the Linnean Society, 2014, 176, 260–276 262 V. CHAUHAN and A. K. PANDEY chyma cells than in the fibrous cells. Fahn & Zohary India. Voucher specimen information is provided with (1955) studied the anatomy of the pod, particularly the the author citation for these taxa in Table 1. Voucher pericarp structure, of > 100 species of Fabaceae. They specimens have been deposited in Delhi University recognized 17 types of legume based mainly on the Herbarium. structure of the sclerenchymatous layer of the peri- carp. For dehiscence to occur, first the sclerenchyma- tous cells and/or the cellulose micelles in their cell POD MORPHOLOGY AND ANATOMY walls must change orientation and, second, there must The length of mature pods (average of ten pods) was be separation tissue present extending into the region measured with the help of a scale. For anatomical of the suture from the inner to the outer epidermis. The studies, pods were fixed in formalin-acetic acid- Downloaded from https://academic.oup.com/botlinnean/article-abstract/176/2/260/2416440 by guest on 15 June 2020 change in orientation leads to unequal swelling and alcohol and dehydrated through an ethanol series shrinking of the cells in different directions, which in (sensu Feder & O’Brien, 1968). Pods were cut into turn causes the pod to shatter. According to Roth small pieces and were then processed in glycol meth- (1977), this arrangement of fibres is responsible for acrylate resin ‘Basic Resin’ infiltration. Sections, the helicoidal bending of the valves. In other words, the 2–3 μm thick, were cut on Microm HM 315 Thermo axis of the bending movement (perpendicular to the Scientific microtome and stained with aqueous tolui- long axis of the fibres) is oriented obliquely to the long dine blue and mounted in DPX. Photographs were axis of the fruits and this leads to helicoidal bending. taken with a microscope Primo Star Zeiss with a Le Roux et al. (2011) concluded that a pattern of Canon digital camera (G10 14.7 MP). dehiscence in which, the orientation of the fibres in the endocarp relative to the longitudinal axis of the fruits POD ANATOMICAL CHARACTERS AND is the major determinant for dehiscence to occur. Also, CHARACTER STATES the presence of different zones of fibres and their orientation relative to one another are also important. The sampled species belong to four clades: the Pal- Yang et al. (1990) observed and concluded that pod aeotropical, Pantropical, Cape, and Tethyan clades of dehiscence was associated with the degree of mesocarp Indigofera (sensu Schrire et al., 2003, 2009) (Table 1). lignification. Gershon (1961) found that indehiscent For character reconstruction, anatomical data were species also exhibit decreased lignification of mesocarp taken from our own observations and from the work cells, and observed that three indehiscent legume of Leite et al. (2009) and Dave & Bennet (1990). A species all lacked separation tissues. Fahn & Zohary total of 41 accessions were included in the present (1955) described the condition of not having a fibrous study. region at the sutures, and only thick-walled paren- Character states recorded for the pod anatomy chyma without a separation layer, as most derived and include: pod type (I, II, III; coded as states 0, 1, 2, thus considered indehiscence as a derived character in respectively) (Table 2). Phylogenetic trees were con- legumes. The species that lacked separation tissue in structed using internal transcribed sequence data of the pod are considered to be tardily dehiscent or the representative species using MrBayes (V. indehiscent and are more derived compared to dehis- Chauhan & A. K. Pandey, unpubl. data). One hundred cent pods. most probable trees were retrieved from the Because the phylogenetic relationships in Indigo- TRPROBS file produced in the Bayesian analyses and fereae are well known (Schrire et al., 2009), an oppor- read into MESQUITE; variation in pod types was tunity exists to evaluate other useful taxonomic examined by ancestral state reconstruction using characters to infer the patterns of evolution. The MESQUITE, version 2.72 (Maddison & Maddison, present study aimed to: (1) to determine the taxo- 2009). Ancestral state reconstruction of characters nomic value of the morphological and anatomical was carried out using maximum parsimony and structures of the pod in Indian Indigofera; (2) to trace maximum likelihood methods. A probability of more the evolution of fruit characters in the tribe Indigo- than 0.60 for a character compiled from the 100 most fereae; and (3) to discuss the role of anatomical fea- probable trees at each node was considered to be the tures in pod dehiscence and the mechanism involved. most probable state at that node. RESULTS MATERIAL AND METHODS POD MORPHOLOGY TAXON SAMPLING Fruits of Indigofera are generally linear but pods may Mature pods of 28 species and four varieties repre- be flat, compressed (Indigofera hochstetteri), curved senting 32 accessions of Indigofera were collected [Indigofera nummulariifolia (L.) Livera ex through our field work carried out in different parts of Alston, Indigofera constricta (Thwaites) Trimen, © 2014 The Linnean Society of London, Botanical Journal of the Linnean Society, 2014, 176, 260–276  Table 1. Plant accessions used for the anatomical study of Indigofera and detailed anatomical description of each plant Pericarp Dehiscent/ Species thickness indehiscent Pod length Pod number Species names Voucher Locality Trichomes (μm) Exocarp Hypodermis Mesocarp Endocarp pod (mm) types 1 Indigofera Chauhan 1468 Madurai Kamraj Pubescent 212.51 Epidermis Single-layered, 4–5 layers, collenchymatous, 4–6 layers, Dehiscent pod 13.18 Type II aspalathoides University single-layered, thick-walled vasculature present sclerenchymatous Vahl ex DC. Campus, thick-walled collenchymatous Tamil Nadu 2 Indigofera Chauhan & Tamil Nadu Pubescent 384.75 Epidermis 3–5 layers, 1st section contains 4–7 6–9 layers, Dehiscent pod 13.68 Type III astragalina AKPandey single-layered, thick-walled layers, collenchymatous sclerenchymatous DC. 1448 thick-walled collenchymatous tissue, 2nd section contains single-layered, large parenchymatous cells 3 Indigofera Chauhan & Rajghad, Glabrous 463.12 Epidermis 2–3 layers, 3–4 layers, narrow 10–12 layers, Dehiscent pod 40.05 Type III atropurpurea AKPandey Sirmaur, H.P. single-layered, thick-walled, collenchymatous cells, sclerenchymatous Buch.-Ham. ex 5019 thick Walled collenchymatous mostly idioblasts are Hornem present 4 Indigofera Chauhan 1472 Megamalai hills, Glabrous 171 Epidermis Single-layered, 4–5 layers, collenchymatous 6–8 layers, Dehiscent pod 10.46 Type II barberi Madurai, single-layered, collenchymatous and parenchymatous, some sclerenchymatous Gamble Tamil Nadu thick-walled cells are idioblasts 5 Indigofera Chauhan 1474 Megamalai hills, Glabrous 328.89 Epidermis 6–8 layers, collenchymatous, 6–9 layers, ? 26.54 Type III cassioides Madurai, single-layered, some cells are idioblasts sclerenchymatous Rottler ex DC. Tamil Nadu thick-walled 6 Indigofera Chauhan 1479 Madurai Kamraj Multicellular as 123.5 Epidermis Single-layered, 2–3 layers, narrow elongated 4–6 layers, Dehiscent pod 18.29 Type II colutea University well single-layered, collenchymatous collenchymatous and sclerenchymatous (Burm.f.) Campus, unicellular thick-walled parenchymatous layer, Merr. Tamil Nadu most cells are idioblasts, vaculature present 7 Indigofera dalzellii Chauhan & Masai plateau, Pubescent 337.25 Epidermis 2–3 layers, 8–10 layers collenchymatous 8–11 layers, Dehiscent pod 23.2 Type III Cooke AKPandey Kohlapur, single-layered, narrow tissue, vasculature present sclerenchymatous 1431 Maharashtra thick-walled elongated collenchymatous cells, most cells are idioblasts 8 Indigofera dosua Chauhan & Sanghra, Glabrous 361 Epidermis 1st section contains 3–4 8–10 layers, Dehiscent pod 22.52 Type III Buch.-Ham. ex AKPandey Sirmaur, H.P. single-layered, layers, collenchymatous sclerenchyma D.Don 5003 thick-walled tissue, 2nd section contains 3–5 layers, elongated, narrow collenchymatous cells, most of them are idioblasts, vascular bundles are present 9 Indigofera exilis Chauhan & Shimla, H.P. Glabrous 248.04 Epidermis 2–3 layers, 4–6 layers, collenchymatous, Up to 8, Dehiscent pod 30.56 Type II Grierson & AKPandey single-layered, collenchymatous narrow, elongated cells sclernchymatous Long 5029 thick-walled 10 Indigofera Chauhan & Shimla, H.P. Pubescent 192.09 Epidermis 1st section contains 3–5 7–8 layers, Dehiscent pod 21.65 Type II gangetica AKPandey single-layered, layers, collenchymatous, sclerenchymatous Sanjappa 5030 thin-walled some cells are idioblasts, tissue © 2014 The Linnean Society of London, Botanical Journal of the Linnean Society, 2014, 176, 260–276 2nd section contains 1–3 layers, narrow elongated parenchymatous tissue, most cells are idioblasts. In this region vascular bundles are present. 11 Indigofera Chauhan & Thummallapalli Glabrous 180.5 Epidermis 3–4 layers, narrow cells, 5–7 layers Dehiscent pod 25.44 Type II glabra L. AKPandey Uranium double-layered, collenchymatous, mostly sclerenchymatous 5098 mining area, thick-walled idioblasts are present, tissue POD STRUCTURE AND EVOLUTION IN INDIGOFERA Anantapur vascular bundles are Dist., Andhra present Pradesh 263 Downloaded from https://academic.oup.com/botlinnean/article-abstract/176/2/260/2416440 by guest on 15 June 2020  Table 1. Continued 264 Pericarp Dehiscent/ Species thickness indehiscent Pod length Pod number Species names Voucher Locality Trichomes (μm) Exocarp Hypodermis Mesocarp Endocarp pod (mm) types 12 Indigofera Chauhan & Belgaon, Pubescent 160.31 Epidermis 4–6 layers, collenchymatous 4–6 layers, Delayed 2.49 Type II glandulosa AKPandey Karnataka single-layered, and parenchymatous, sclerenchymatous dehiscent Wendl. var. 1442 thin-walled narrow, elongated cells, sykesii Griffith most cells are idioblasts ex Baker 13 Indigofera Chauhan 5036 Shimla, H.P. Glabrous 392.63 Epidermis 1st section contains 1–2 8–10 layers, Dehiscent pod 50.45 Type III hebepetala single-layered, layers, rounded sclerenchyma Benth. ex Baker thick-walled collenchymatous cells, 2nd var. glabra Ali section contains 1–2 layers, rounded collenchymatous cells, most cells are idioblasts, 3rd section contains 4–5 layers, narrow elongated parenchymatous cells, vascular bundles present 14 Indigofera Chauhan & Badalta, Glabrous 301 Epidermis 6–10 layers, 11–14 layers, Dehiscent pod 50.04 Type III hebepetala AKPandey Sirmaur, H.P. single-layered, collenchymatous, most sclerenchymatous V. CHAUHAN and A. K. PANDEY Benth. ex Baker 5033 thick-walled cells are idioblasts var. hebepetala 15 Indigofera Chauhan & Nohradhar, Glabrous 508.91 Epidermis 4–5 layers, 4–8 layers, narrow elongated 8–10 layers, ? 31.86 Type III heterantha AKPandey Sirmaur, H.P. single-layered, thick-walled collenchymatous and sclerenchyma Wallich ex 5014 thick-walled collenchymatous parenchymatous, most Brandis cells are idioblasts 16 Indigofera Chauhan 5032 Budgaam, J & Glabrous 318.25 Epidermis 1–2 layers, ? 8–10 ? 4.02 Type III himalayensis K single-layered, thick-walled sclerenchymatous Ali thick-walled collenchymatous 17 Indigofera Chauhan & Hissar Dist., Pubescent 47.5 Epidermis 1st section contains 2–4 3–5 layers, Delayed 11.56 Type I hochstetteri AKPandey Punjab single-layered, layers, collenchymatous, sclerenchymatous dehiscent Baker 6002 thick-walled most cells are idioblasts, vasculature present 18 Indigofera Chauhan & Bannerghatta Glabrous 228 Epidermis Double-layered 1st section contains 2–3 4–6 layers, Delayed 22.5 Type II karnatakana AKPandey hills, single-layered, thick-walled layers, parenchymatous, sclerenchymatous dehiscent Sanjappa 5046 Karnataka thick-walled collenchymatous 2nd section contains 3–4 layers narrow, collenchymatous most cells are idioblasts 19 Indigofera Chauhan 1465 Kannalti, Pubescent 184.3 Epidermis Single-layered 1st section contains 4–5 6–7 layers, Dehiscent pod 7.42 Type II karuppiana Niligris Dist., single-layered, thick-walled layers, narrow, elongated sclerenchyma Pallithanam Tamil Nadu thick-walled collenchymatous parenchymatous tissue, most cells are idioblasts 20 Indigofera Chauhan & University Pubescent 167.77 Epidermis Single-layered, 1st section contains 2–3 3–6 layers, Dehiscent pod 2.1 Type II linifolia (L. f.) AKPandey Campus single-layered, thick-walled layers, narrow elongated sclerenchymatous Retz. var. 1446 Garden, thick-walled collenchymatous collenchymatous cells, campbelli Wight Kohlapur, most cells are idioblats, ex Baker Maharashtra vasculature is present in this layer, 2nd section contains single-layered rounded collenchymatous cells 21 Indigofera Chauhan & Madurai Kamraj Pubescent 202.35 Epidermis 1–2 layers, 1–2 layers, collenchymatous, 2–6 layers, Dehiscent pod 2.1 Type II linifolia (L. f.) AKPandey University single-layered, collenchymatous some cells are idioblasts sclerenchymatous Retz. var. 1470 Campus, thick-walled linifolia Tamil Nadu 22 Indigofera Chauhan 1498 Kalkadu, 352.45 7–9 layers, 15.35 Type III longiracemosa Tirunelveli sclerenchymatous Boivin ex Baill. Dist., Tamil Nadu © 2014 The Linnean Society of London, Botanical Journal of the Linnean Society, 2014, 176, 260–276 Downloaded from https://academic.oup.com/botlinnean/article-abstract/176/2/260/2416440 by guest on 15 June 2020  23 Indigofera Chauhan & Thummallapalli Pubescent 155.13 Epidermis 4–8 layers, collenchymatous 3–6 layers, Dehiscent pod 12.42 Type II oblongifolia AKPandey Uranium single-layered, sclerenchymatous Forssk. 5099 mining area, thick-walled Anantapur Dist., Andhra Pradesh 24 Indigofera Chauhan & Goa University Sparsely 129.77 Epidermis Single-layered, 1–2 layers, narrow, 4–6 layers, Dehiscent pod 9.72 Type II prostrata Willd. AKPandey Campus, Goa pubecent single-layered, collenchymatous elongated, collenchymatous sclerenchymatous 1451 thick-walled and parenchymatous, most cells are idioblasts, vascular bundles present 25 Indigofera Chauhan& Ramgard, Pubescent 194.18 Epidermis 1–2 layers, 4–6 layers, collenchymatous 4–6 layers, Dehiscent pod 7.86 Type II sessiliflora DC. AKPandey Jaisalmer single-layered, thick-walled, tissue. Vasculature present sclerenchymatous 6001 Dist., thick-walled collenchymatous Rajasthan 26 Indigofera Chauhan 1467 Kannalti, Tamil Glabrous 215.65 Epidermis 1st section contains 2–3 6–8 layers, Dehiscent pod 23.9 Type II tinctoria L. Nadu single-layered, layers, collenchymatous sclerenchymatous thick-walled tissue, 2nd section contains 2–4 layers, narrow large elongated parenchymatous, most cells are idioblasts 27 Indigofera Chauhan & Sutghatti ghat, Pubescent 181.45 Epidermis Single-layered, 3–4 layers, narrow elongated 6–8 layers, Dehiscent pod 7.48 Type II trifoliata L. AKPandey Kohlapur, single-layered, thick-walled, collenchymatous, most sclerenchymatous 1438 Maharashtra thick-walled collenchymatous cells are idioblasts 28 Indigofera Chauhan & Girgaon, Pubescent 123.5 Epidermis Single-layered, 3–4 layers, collenchymatous, 4–6 layers, ? 7.76 Type II trifoliata L. var. AKPandey Kohlapur, single-layered, thick-walled, some cells are idioblasts sclerenchymatous duthiei 1429 Maharashtra thick-walled collenchymatous (Drumm. ex Naik) Sanjappa 29 Indigofera trita L. Chauhan 1460 Marudhamalai Pubescent 181.64 Epidermis 1–2 layers, 6–8 layers, narrow elongated 4–6 layers, Delayed 35.67 Type II f. var. scabra hills, Tamil single-layered, thick-walled, collenchymatous, sclerenchymatous dehiscent (Roth) Ali Nadu thick-walled collenchymatous vasculature present 30 Indigofera trita L. Chauhan 1471 American Pubescent 224.39 Epidermis 1–2 layers, 4–5 layers, collenchymatous 5–7 layers, Dehiscent pod 24.84 Type II f. var. trita College, Tamil single-layered, thick-walled, and parenchymatous cells sclerenchymatous Nadu thick-walled collenchymatous tissue 31 Indigofera Chauhan 1459 Madhukkarai Pubescent 95.95 Epidermis 3 layers, collenchymatous 4–5 layers, ? 6.84 Type I uniflora hills, Tamil single-layered, sclerenchymatous Buch.-Ham. ex Nadu thick-walled Roxb. 32 Indigofera wightii Chauhan 1473 Megamalai hills, Pubescent 396.15 Epidermis 1st section conatins 4–6 7–9 layers, Dehiscent pod 23.18 Type III Graham ex Madurai, single-layered, layers, collenchymatous sclerenchymatous Wight & Arn. Tamil Nadu thick-walled tissue, 2nd section contains 3–5 layers, elongated large © 2014 The Linnean Society of London, Botanical Journal of the Linnean Society, 2014, 176, 260–276 parenchymatous cells Vascular bundles are present POD STRUCTURE AND EVOLUTION IN INDIGOFERA 265 Downloaded from https://academic.oup.com/botlinnean/article-abstract/176/2/260/2416440 by guest on 15 June 2020 266 V. CHAUHAN and A. K. PANDEY Table 2. Character matrix showing the character states for all the species used in ancestral state reconstruction in Mesquite Taxon/character Pod type Taxon/character Pod type Cyamopsis tetragonoloba FJ769262 2 Indigofera heterantha EU729571 2 Indigastrum argyroides EU729488 2 Indigofera heterotricha EU729535 ? Indigastrum candidissimum EU729489 2 Indigofera himalayensis AF521770 2 Indigastrum costatum AF521716 2 Indigofera hirsuta EU729546 0 Indigastrum fastigiatum EU729490 2 Indigofera hochstetteri EU729656 0 Downloaded from https://academic.oup.com/botlinnean/article-abstract/176/2/260/2416440 by guest on 15 June 2020 Indigofera dosua AF534790 2 Indigofera karnatakana EU729544 1 Indigofera himalayensis AF534792 2 Indigofera lespedezioides AF521780 1 Indigofera aspalathoides JQ945958 1 Indigofera linifolia EU729629 1 Indigofera astragalina EU729545 2 Indigofera linifolia JQ945964 1 Indigofera astragalina JQ945966 2 Indigofera linnaei EU729670 ? Indigofera atropurpurea EU729575 2 Indigofera linnaei JQ945960 ? Indigofera barberi JQ945961 1 Indigofera longiracemosa AF521786 2 Indigofera bongardiana EU729661 ? Indigofera longiracemosa AY124764 2 Indigofera cassioides EU729573 2 Indigofera microcarpa EU729630 1 Indigofera cassioides JQ945965 2 Indigofera miniata EU729663 ? Indigofera colutea AF521776 1 Indigofera nummulariifolia EU729631 ? Indigofera colutea JQ945956 1 Indigofera oblongifolia AF521778 1 Indigofera concava EU729619 ? Indigofera prostrata JQ945972 1 Indigofera cordifolia AF521741 ? Indigofera schimperi AF274696 ? Indigofera cordifolia JQ945963 ? Indigofera semitrijuga EU729669 ? Indigofera cuneifolia AF521749 ? Indigofera sessiliflora EU729642 1 Indigofera dalzellii AF521793 2 Indigofera spicata EU729671 1 Indigofera dalzellii JQ945962 2 Indigofera squalida EU729633 ? Indigofera denudata EU729617 ? Indigofera suffruticosa AF467051 1 Indigofera dosua AF521771 2 Indigofera tinctoria AF521775 1 Indigofera drepanocarpa EU729632 ? Indigofera trifoliata JQ945971 1 Indigofera gairdnerae EU729507 ? Indigofera trita AF521745 1 Indigofera glabra EU729504 1 Indigofera trita EU729681 1 Indigofera glandulosa EU729634 1 Indigofera truxillensis EU729602 1 Indigofera glandulosa var. skyseii JQ945967 1 Indigofera uniflora JQ945959 0 Indigofera hebepetala AF521768 2 Indigofera wightii EU729519 2 Indigofera hebepetala AF534793 2 Indigofera wightii JQ945957 2 Coding for the character states – pod types: 0, pod type I; 1, pod type II; 2, pod type III. Indigofera suffruticosa Mill., and Indigofera trita var. Indigofera santapaui Sanjappa, Indigofera thothath- scabra] or globose [Indigofera cordifolia Heyne ex rii Sanjappa, Indigofera tirunelvelica Sanjappa), pods Roth, Indigofera linifolia (Fig. 2). The cross-section of have glands on the surface. All the species having the pod is usually cylindric, subcylindric or sub- gland dotted pods are trifoliolate species. Multicellu- tetragonous, except Indigofera nummulariifolia in lar, erect, gland-tipped hairs are present on pods in which it is triquetrous. The pods are usually Indigofera argentea and Indigofera colutea. In some adpressed hairy, except in some species where they species of Indigofera, mature fruits have broad are glabrous (Indigofera atropurpurea, Indigofera cas- sutures (Indigofera argentea Burm.f., Indigo- sioides, Indigofera cedrorum Dunn, Indigofera cylin- fera arrecta Hochst. ex A.Rich, Indigofera bracteata dracea Graham ex Baker, Indigofera exilis, Graham ex Baker, I. colutea, Indigofera dosua, I. suf- Indigofera glabra, Indigofera hamiltonii Graham ex fruticosa, Indigofera tirunelvelica, Indigofera zollin- Duthie & Prain, Indigofera hebepetala, Indigo- geriana Miq.), fruits with obscurely or shortly winged fera himalayensis, Indigofera lacei Craib). The pod is sutures [Indigofera dalzellii, Indigofera glabra, deflexed or spreading or ascending, dehiscent or inde- Indigofera karuppiana, Indigofera prostrata, Indigo- hiscent. In some species (Indigofera barberi, Indigo- fera thothathrii, Indigofera trifoliata var. duthiei], fera glandulosa, Indigofera karuppiana, Indigofera fruits with prominently winged sutures (Indigo- pedicellata Wight & Arn., Indigofera prostrata, fera bracteata var. khasiana Sanjappa, Indigofera © 2014 The Linnean Society of London, Botanical Journal of the Linnean Society, 2014, 176, 260–276  POD STRUCTURE AND EVOLUTION IN INDIGOFERA 267 Downloaded from https://academic.oup.com/botlinnean/article-abstract/176/2/260/2416440 by guest on 15 June 2020 Figure 2. Morphological variation of fruits of genus Indigofera. A. Indigofera trita var. scabra (1460). B, Indigofera wightii (1473). C, Indigofera cordifolia (1432). D, Indigofera linifolia (1470). E, Indigofera linnaei (1469). F, Indigofera cassioides (1474). G, Indigofera karuppiana (1465). H, Indigofera hendecaphylla (1477). I, Indigofera trifoliata (1438). J, Indigofera trita var. trita (1471). K, Indigofera astragalina (1448). L, Indigofera dosua (1488). M, Indigofera tinctoria (1475). N, Indigofera heterantha (1485). O, Indigofera colutea (1479). P, Indigofera dalzellii (1431). Q, Indigofera aspalathoides (1468). R, Indigofera prostrata (1451). S, Indigofera glandulosa (1442). T, Indigofera barberi (1472). U, Indigofera trifoliata var. duthiei (1429). V, Indigofera uniflora (1459). W, Indigofera himachalensis (1487). Scale bar = 2 mm. glandulosa, Indigofera trifoliata) or spiny processes Exocarp along the sutures (Indigofera nummulariifolia). The exocarp generally consists of a single-layered epidermis, except in I. glabra where it is biseriate. The exocarp is mostly thick-walled, except Indigofera POD ANATOMY gangetica and I. glandulosa var. sykesii, in which it is Fruits in Indigofera are relatively thin- to thick- thin-walled. The hypodermis may be present or walled. Anatomically, the pericarp is distinguishable absent. If present, then it is usually single-layered, into exocarp, mesocarp and endocarp. but sometimes multiple layers are present (Indigo- © 2014 The Linnean Society of London, Botanical Journal of the Linnean Society, 2014, 176, 260–276 268 V. CHAUHAN and A. K. PANDEY fera astragalina, I. atropurpurea, Indigofera dalzellii, sclerenchymatous layers in the endocarp. These two I. exilis, Indigofera heterantha and Indigofera karna- characteristics are indicative of a dehiscent pod. takana). The multilayered exocarp is composed of However, in some taxa (I. hochstetteri, I. karnata- thick-walled collenchymatous cells. kana, I. glandulosa var. sykesii, and I. trita var. scabra), which show a tardily dehiscent or indehis- Mesocarp cent condition, no separation tissue is found and there The mesocarp is composed of three or four to eight- to is mostly a low to intermediate number of scleren- ten-layered collenchymatous tissue but, in some chyma layers present in the endocarp. Two Neotropi- species, parenchymatous tissue is also present (e.g., cal Indigofera spp., I. microcarpa Desv. (winged pods) Indigofera astragalina, Indigofera barberi, Indigofera and I. suffruticosa (broad sutures but no wings), are Downloaded from https://academic.oup.com/botlinnean/article-abstract/176/2/260/2416440 by guest on 15 June 2020 colutea, Indigofera gangetica, Indigofera glandulosa tardily dehiscent because there is no separation var. sykesii, Indigofera hebepetala var. glabra, Indigo- tissue present (Leite et al., 2009). Roth (1977) fera heterantha, Indigofera karnatakana, Indigofera reported two anatomical features that appear to karuppiana, Indigofera prostrata, Indigofera tincto- reduce the tendency to dehisce in legumes. The first is ria, Indigofera trita var. trita, Indigofera wightii). a longer fruit and the second is a strongly bent fruit. Vascular bundles and most of the idioblasts are The indehiscent I. trita var. scabra possesses a long present in the mesocarp region. and strongly curved pod. Endocarp EVOLUTION OF POD ANATOMICAL CHARACTERS The endocarp is composed of a variable number of sclerenchyma layers, ranging from three to five to ten The evolutionary pattern of pod types was inferred to 12. The most common endocarp cell layer number from ancestral state reconstruction (Fig. 6), carried in Indigofera is six to eight. out on the 100 most probable trees from Bayesian On the basis of pericarp thickness and number of analyses (TRPROBS file) and the probabilities of a sclerenchymatous layers in the endocarp, three basic particular ancestral state at specific nodes (Table 5). fruit types can be recognized: pod type I, II, and III. In the ancestor to Cyamopsis DC. + Indigastrum Type I (thin pericarp and three to five sclerenchyma- Jaub. & Spach + Indigofera, however, the two states tous layers in the endocarp); type II (intermediary pod type II and III are present but pod type III pericarp thickness and six to eight sclerenchymatous probability (P = 0.6245) is higher than for other layers); and type III (thick pericarp and more than states. In Indigastrum and Cyamopsis, the pod is of eight sclerenchymatous layers) (Figs 3, 4, 5; Table 3). type III. Pod type II was present (P = 0.7471) in The anatomical description for the genus is sum- ancestral Indigofera. The common ancestors of clades marized in Table 4 with an indication of the fruit C (P = 0.7311), D (P = 0.9784), and E (P = 0.9542) pericarp type (fruit type classification for all species have pod type II present, whereas the ancestor of investigated is listed in the Table 1). The distribution clade F had pod type III (P = 0.6033). The transition of fruit pericarp types in the tribe is shown in from pod type II to pod type III takes place at node f. Figure 6. There is a reversal in I. wightii (clade E) and I. dal- zellii (clade C), which have pod type III. In I. karna- takana and I. tinctoria–I. truxillensis Kunth– POD DEHISCENCE I. suffruticosa (clade F), pod type II has evolved Both dehiscent and tardily dehiscent pods are present independently from the pod type III condition. In in Indigofera, which generally shows normal explo- Indigofera uniflora (clade E) and I. hochstetteri (clade sive dehiscence as a mean of dispersal of seeds, C), pod type I has evolved independently from the pod although some species show adaptations for dispersal type II condition and, simultaneously, in Indigofera by wind (I. cordifolia, I. linifolia, I. glandulosa, and hirsuta L. (clade F), pod type I has evolved indepen- I. linnaei Ali). Some Indigofera spp. are similar in dently from pod type III. having small, light weighted, few seeded, indehiscent or tardily dehiscent fruits with persistent calyces and DISCUSSION corollas with the pod embellished with broad sutures, leading to longitudinal fringed wings, appearing to be In Indigofera, pod morphology is variable and char- adapted to dispersal by wind, water or gravity. All acters have little diagnostic value at the generic level. these fruit characters indicate a shift to pods playing The genus can be identified by a combination of a role in seed dispersal. The whole pod acts as a characters, and fruit characters on their own have diaspore that can easily blown away by wind. In limited value (Gillett, 1958; De Kort & Thijsse, 1984; Indigofera, pods usually have separation tissue Sanjappa, 1995; Schrire, 1995; Wilson & Rowe, 2004, present along the sutures and a variable number of 2008). An example of nonhomologous similarity was © 2014 The Linnean Society of London, Botanical Journal of the Linnean Society, 2014, 176, 260–276  POD STRUCTURE AND EVOLUTION IN INDIGOFERA 269 Downloaded from https://academic.oup.com/botlinnean/article-abstract/176/2/260/2416440 by guest on 15 June 2020 Figure 3. Transverse sections of fruits in Indigofera. Paleotropical clade with a type I pericarp (A), type II pericarp (B, C, D, E), and type III pericarp (F). A, Indigofera uniflora [Chauhan 1459]. B, Indigofera glabra [Chauhan & AKPandey 5098]. C, Indigofera colutea [Chauhan 1479]. D, Indigofera aspalathoides [Chauhan 1468]. E, Indigofera barberi [Chauhan 1472]. F, Indigofera wightii [Chauhan 1473]. Scale bar = 50 μm. revealed by the presence of flattened and compressed 2009)]. However, some trends were observed by us pods that are found in Indigofera, Cyamopsis, and and three basic pericarp types were identified within Indigastrum. In Cyamopsis tetragonoloba Taub., the tribe. The distribution of these types across the fruits are longitudinally ridged and septate between tribe is not congruent with current phylogenetic seeds. analyses, as shown in Figure 6. The anatomy of the pericarp is too conservative to Our anatomical studies on the Indigofera spp. be used diagnostically at the generic level. In Indigo- reveal that the genus is closely related to Cyamopsis– fera glabra, the exocarp is biseriate, a character also Indigastrum clade of Schrire et al. (2003, 2009). All present in the Neotropical species Indigofera lespe- the species that were sampled for the study belong to dezioides Kunth (Leite et al., 2009). The exocarp is four clades (Palaeotropical, Pantropical, Cape, and mostly thin-walled in Neotropical species [Indigo- Tethyan clades of Indigofera as given by Schrire et al., fera campestris Bong. ex Benth., I. hirsuta, I. lespe- 2003, 2009). The whole Palaeotropical–Pantropical, dezioides, I. spicata Forssk. (introduced to the New Cape, and Tethyan clades form polytomy with each World), I. suffruticosa and I. truxillensis (Leite et al., other. Ancestral state reconstructions of pod type © 2014 The Linnean Society of London, Botanical Journal of the Linnean Society, 2014, 176, 260–276 270 V. CHAUHAN and A. K. PANDEY Downloaded from https://academic.oup.com/botlinnean/article-abstract/176/2/260/2416440 by guest on 15 June 2020 Figure 4. Transverse sections of fruits in Indigofera. Pantropical clade with a type II pericarp (A, B), and type III pericarp (C, D, E, F, G, H). A, Indigofera karnatakana [Chauhan & AKPandey 5046]. B, Indigofera tinctoria [Chauhan 1467]. C, Indigofera astragalina [Chauhan & AKPandey 1448]. D, Indigofera heterantha [Chauhan & AKPandey 5014]. E, Indigofera hebepetala var. hebepetala [Chauhan & AKPandey 5033]. F, Indigofera hebepetala var. glabra [Chauhan 5036]. G, Indigofera dosua [Chauhan & AKPandey 5003]. H, Indigofera himalayensis [Chauhan 5032]. Scale bar = 50 μm. © 2014 The Linnean Society of London, Botanical Journal of the Linnean Society, 2014, 176, 260–276  POD STRUCTURE AND EVOLUTION IN INDIGOFERA 271 Downloaded from https://academic.oup.com/botlinnean/article-abstract/176/2/260/2416440 by guest on 15 June 2020 Figure 5. Transverse sections of fruits in Indigofera: Tethyan clade with a type I pericarp (A), type II pericarp (B, C, D, E, F, G) and type III pericarp (H). A, Indigofera hochstetteri [Chauhan & AKPandey 6002]. B, Indigofera trifoliata [Chauhan & AKPandey 1438]. C, Indigofera prostrata [Chauhan & AKPandey 1451]. D, Indigofera glandulosa var. sykesii [Chauhan & AKPandey 1442]. E, Indigofera trita var. trita [Chauhan 1471]. F, Indigofera linifolia [Chauhan & AKPandey 1446]. G, Indigofera sessiliflora [Chauhan& AKPandey 6001]. H, Indigofera dalzellii [Chauhan & AKPandey 1431]. Scale bar = 50 μm. © 2014 The Linnean Society of London, Botanical Journal of the Linnean Society, 2014, 176, 260–276 272 V. CHAUHAN and A. K. PANDEY Table 3. Characteristics of the three basic fruit types recognized in the genus Indigofera Pod Pericarp Sclerenchymatous type thickness layers Fruit structure Distribution in the genus Type I Below Three to Fruits relatively thin-walled, trichomes Present in Indigofera uniflora and 100 μm five present. Exocarp: single-layered Indigofera hochstetteri. layers epidermis, thick- walled. Hypodermis absent. Mesocarp: only collenchymatous cells. Endocarp: three- to five layered, Downloaded from https://academic.oup.com/botlinnean/article-abstract/176/2/260/2416440 by guest on 15 June 2020 sclerenchymatous. Delayed dehiscent pod (Figs 3, 5) Type II 100– Six to eight Fruits are of intermediatary thickness, Predominantly present in 300 μm layers trichomes absent/present. Exocarp: one- Indigofera spp. or or two-layered epidermis, thin to thick-walled. Hypodermis absent/present, single-layered to two- to three-layered thick-walled collenchymatous. Mesocarp: composed of collenchymatous cells or both collenchymatous and parenchymatous cells. Endocarp: six- to eight-layered, sclerenchymatous. Dehiscent or delayed dehiscent pod (Figs 3, 4, 5) Type III Above More than Fruits relatively thick-walled, trichomes Present in Indigofera astragalina, 300 μm eight absent/present. Exocarp: epidermis Indigofera atropurpurea, single-layered, thick- walled. Hypodermis Indigofera cassioides, Indigofera absent/present, single to four- to dalzellii, Indigofera dosua, five-layered thick-walled collenchymatous. Indigofera hebepetala, Indigofera Mesocarp: comprises collenchymatous heterantha, Indigofera cells or both collenchymatous and himalayensis, Indigofera parenchymatous cells. Endocarp: eight- to longiracemosa, and Indigofera 11-layered sclerenchymatous. Dehiscent wightii pod (Figs 3, 4, 5) show that the common ancestor of tribe Indigoferae mediate pods (10–20 mm) has intermediate endocarp has pod type III. The common ancestor of Indigofera (e.g. I. karuppiana, I. glabra, I. trifoliata, I. trita var. had pod type II (P = 0.7471) and a change occurred in trita). Pericarp thickness is directly correlated with the ancestor of clade F to pod type III (P = 0.6033). number of sclerenchymatous layers in the endocarp. Species of Indigastrum and Cyamopsis have a type Molecular and morphological data (Schrire et al., III pericarp, whereas, in Indigofera, all three types (I, 2009) indicated that Indigastrum parviflorum II, III) are present. Type II is predominant and occurs (B.Heyne ex Wight & Arn.) Schrire should be in the Palaeotropical and Tethyan clades, and inde- excluded from Indigofera, although its placement in pendently evolved in I. karnatakana, I.truxillensis, Indigastrum is not supported by fruit morphology or I. suffruticosa, and I. tinctoria; type I occurs in three anatomy (V. Chauhan & A. K. Pandey, unpubl. data). independent lineages (I. uniflora, I. hirsuta, and The type III pericarp (present in the early diverging I. hochstetteri) and type III is observed in Indigas- lineages of the tribe) represents the least derived state, trum, Cyamopsis, and the pantropical clade with an whereas type I and II are more derived. Fahn & Zohary independent reversal to type III in I. wightii and (1955) considered the presence of multiple cell layers of I. dalzellii. sclerenchyma in the endocarp to be the primitive state The three parameters of the pod (pod size, pericarp in legumes and its loss to be derived. Our results also thickness, and number of sclerenchyma layers in the support the earlier findings of Fahn & Zohary (1955), endocarp) are correlated. There is a correlation indicating that the small pod, thin pericarp, and fewer between the size of the pod (length) and the thickness sclerenchymatous layers in the endocarp (three to five) of the endocarp (sclerenchyma tissue) because all the (pod type I) and the intermediate pod condition and large pods (> 20 mm) have a thick endocarp, small thin- to thick-walled and five to eight sclerenchyma- pods (< 10 mm) have a thinner endocarp and inter- tous layers in the endocarp (pod type II) are more © 2014 The Linnean Society of London, Botanical Journal of the Linnean Society, 2014, 176, 260–276  Table 4. Summary of pericarp characters of genus Indigofera Pericarp thickness in micrometers Exocarp Hypodermis Mesocarp Endocarp Dehiscence Pod types + 3–5 layers, thin ++ 6–8 layers, + < 100 μm Number of Cell walls Parenchyma Collenchyma intermediate +Dehiscent pod ++ 100–300 μm exocarp -thin _absent –absent –absent +++ > 8 layers, –Delayed Species names +++ > 300 μm layers +thick +present +present +present thick dehiscent pod Type I/II/III Indigofera aspalathoides Vahl ex DC. ++ One + + _ + ++ + Type II Indigofera astragalina DC. +++ One + + + + +++ + Type III Indigofera atropurpurea Buch.-Ham. ex Hornem +++ One + + _ + +++ + Type III Indigofera barberi Gamble ++ One + + + + ++ + Type II Indigofera cassioides Rottler ex DC. +++ One + _ _ + +++ ? Type III Indigofera colutea (Burm.f.) Merr. ++ One + + + + ++ + Type II Indigofera dalzellii T.Cooke +++ One + + _ + +++ + Type III Indigofera dosua Buch.-Ham. ex D.Don +++ One + _ _ + +++ + Type III Indigofera exilis Grierson & Long ++ One + + _ + ++ + Type II Indigofera gangetica Sanjappa ++ One _ _ + + ++ + Type II Indigofera glabra L. ++ Two + _ _ + ++ + Type II Indigofera glandulosa Wendl. var. sykesii Griffith ex ++ One _ _ + + ++ _ Type II Baker Indigofera hebepetala Benth. ex Baker var. glabra Ali +++ One + _ + + +++ + Type III Indigofera hebepetala Benth. ex Baker var. hebepetala +++ One + _ _ + +++ + Type III Indigofera heterantha Wallich ex Brandis +++ One + + + + +++ ? Type III Indigofera himalayensis Ali +++ One + + +++ ? Type III Indigofera hochstetteri Baker + One + _ _ + + _ Type I Indigofera karnatakana Sanjappa ++ One + + + + ++ _ Type II Indigofera karuppiana Pallithanam ++ One + + + _ ++ + Type II Indigofera linifolia (L. f.) Retz. var. campbelli Wight ex ++ One + + _ + ++ + Type II Baker Indigofera linifolia (L. f.) Retz. var. linifolia ++ One + + _ + ++ + Type II Indigofera longiracemosa Boivin ex Baill. +++ +++ ? Type III Indigofera oblongifolia Forssk. ++ One + + _ + ++ + Type II Indigofera prostrata Willd. ++ One + + + + ++ + Type II Indigofera sessiliflora DC. ++ One + + _ + ++ + Type II Indigofera tinctoria L. ++ One + _ + + ++ + Type II © 2014 The Linnean Society of London, Botanical Journal of the Linnean Society, 2014, 176, 260–276 Indigofera trifoliata L. ++ One + + _ + ++ + Type II Indigofera trifoliata L. var. duthiei (Drumm. ex Naik) ++ One + + _ + ++ ? Type II Sanjappa Indigofera trita L. f. var. scabra (Roth) Ali ++ One + + _ + ++ _ Type II Indigofera trita L. f. var. trita ++ One + _ + + ++ + Type II Indigofera uniflora Buch.-Ham. ex Roxb. + One + _ _ + + ? Type I POD STRUCTURE AND EVOLUTION IN INDIGOFERA Indigofera wightii Graham ex Wight & Arn. +++ One + _ + + +++ + Type III Type I, below 100 μm and 3–5 sclerenchymatous layers; type I, 100–300 μm and 3–8 layers; type II, above 300 μm and > 8 layers. 273 Downloaded from https://academic.oup.com/botlinnean/article-abstract/176/2/260/2416440 by guest on 15 June 2020 274 V. CHAUHAN and A. K. PANDEY Downloaded from https://academic.oup.com/botlinnean/article-abstract/176/2/260/2416440 by guest on 15 June 2020 Figure 6. Phylogram constructed from 1998 trees in MrBayes. All the clades are labelled. Numbers on the branches indicate the posterior probabilities (pp). All the coloured branches correspond to the four clades formed by Schrire et al., 2009. A black line shows the evolution of the pod type character at specific nodes carried out from the ancestral state reconstruction by parsimony and likelihood methods in MESQUITE. The likelihoods were calculated for the 100 most probable trees in the TRPROBS file in MrBayes. The character states marked show the most probable states at that node. Table 5. Summary of evolution of pod types in tribe Indigoferae Pod types Pod type I Pod type II Pod type III A – Recent common ancestor 0.0287652 in 100 trees 0.3467892 in 100 trees 0.624524 in 100 trees to Cyamposis + Indigastrum + Indigofera clade B – Ancestral Indigofera 0.0077725 in 100 trees 0.747155 in 100 trees 0.24512 in 100 trees C – Ancestral 0.006239 in 100 trees 0.731111 in 100 trees 0.262650 in 100 trees Palaeotropical + Pantropical clade D – Ancestral Tethyan clade 0.00397931 in 100 trees 0.97843279 in 100 trees 0.0175879 in 100 trees E – Ancestral Palaeotropical 0.0016906 in 100 trees 0.9542524 in 100 trees 0.044057 in 100 trees clade F – Ancestral Pantropical 0.0049752 in 100 trees 0.3916416 in 100 trees 0.6033832 in 100 trees clade Maximum likelihood values for reconstruction of pod types (Pod type I, II, III) at specific nodes of the tree (Fig. 6) taken from the 100 most probable trees from the TRPROBS file retrieved from MrBayes. Probabilities which are more than 0.6 are in bold because they are considered to be the most probable state for that node. © 2014 The Linnean Society of London, Botanical Journal of the Linnean Society, 2014, 176, 260–276  POD STRUCTURE AND EVOLUTION IN INDIGOFERA 275 derived compared to the large pod type with thick Lotus species and their interspecific hybrids. PhD Thesis, pericarp and more sclerenchymatous layers in the Cornell University. endocarp (more than eight) (pod type III). It is evident Gillett JB. 1958. Indigofera (Microcharis) in tropical Africa: from character reconstruction that an increase in with the related genera Cyamopsis and Rhynchotropis. Kew pericarp thickness and number of sclerenchyma layers Bulletin Additional Series 1: 1–166. (pod type III) is probably a plesiomorphic trait of the Guttenberg HV. 1971. Bewegungsgewebe und Perzeptions – genus and a decrease in pericarp thickness and organe – encyclopedia of plant anatomy (Hand. D. Pflanzenanat, begr V K Linsbauer) 2 Aufl, hrsg VW Zim- number of sclerenchyma layers (pod type II and pod mermann Bd VI, Teil 1, VIII 332 S. Stuttgart: Gebruder type I) is apomorphic for the tribe. Borutnaeger. In Indigofera, dehiscence is caused by a separation Downloaded from https://academic.oup.com/botlinnean/article-abstract/176/2/260/2416440 by guest on 15 June 2020 Kirkbride JH Jr, Gunn C, Weitzman AL. 2003. Fruits and layer present at the dorsal and ventral sutures except seeds of genera in the subfamily Faboideae (Fabaceae). in some species (I. hochstetteri, I. karnatakana, Technical Bulletin 1890: 1–115, 1030–1055. I. glandulosa var. sykesii, I. trita var. scabra) where Le Roux MM, Van Wyk B-E, Boatwright JS, Tilney PM. no separation tissue is present and the species show 2011. The systematic significance of morphological and ana- a tardily dehiscent or an indehiscent condition. The tomical variation in fruits of Crotalaria and related genera indehiscent pod type is considered to be apomorphic. of tribe Crotalarieae (Fabaceae). Botanical Journal of the Linnean Society 165: 84–106. Leite VG, Marquiafavel FS, Moraes DP, Teixeira SP. ACKNOWLEDGEMENTS 2009. Fruit anatomy of Neotropical species of Indigofera (Leguminosae, Papilionoideae) with functional and taxo- Grant support comprising an R&D Grant of the nomic implications. Journal of the Torrey Botanical Society University of Delhi to AKP is thankfully 136: 203–211. acknowledged. Maddison WP, Maddison DR. 2009. Mesquite: a modular system for evolutionary analyses, Version 2.72. Available at: http://mesquiteproject.org Pate JS, Kuo J. 1981. Anatomical studies of legume pods – REFERENCES a possible tool in taxonomic research. In: Polhill RM, Raven Buckovic RG. 1952. Some of the morphological and agro- PH, eds. Advances in legume systematics, Part 2. 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