Development and functional anatomy of pods of Colophospermum mopane (Caesalpinioideae: Dietarieae)
A. Jordaan A C and H. Krüger BA Electron Microscope Unit, University of Botswana, Private Bag 0022, Gaborone, Botswana.
B School for Environmental Sciences and Development, Botany, Potchefstroom University for Christian Higher Education, Potchefstroom, 2520, South Africa.
C Corresponding author. Email: jordaana@mopipi.ub.bw
Australian Journal of Botany 53(1) 55-67 https://doi.org/10.1071/BT04027
Submitted: 18 February 2004 Accepted: 25 August 2004 Published: 18 February 2005
Abstract
Pod development of Colophospermum mopane was studied from its initiation until it was fully developed and completely filled by the seed. After fertilisation, meristematic activity in various regions of the pericarp causes fruit enlargement. The carpel symmetry and vascularisation displayed by the pods is of the follicular type. One dorsal and two unfused ventral bundles supply the pod. The funicle originates from one of the ventral bundles. The vascular supply of both the dorsal and ventral bundles is elaborate as secondary growth of a cambium increases the diameters of the bundles significantly. During early stages of fruit development the 3–5 innermost parenchyma layers of the mesophyll that borders the inner epidermis differentiate into small thin-walled parenchyma cells that differ considerably in size from the larger outer parenchymatous mesophyll cells. The inner zone of small parenchyma cells eventually differentiates into several collenchyma layers. At a later stage, the innermost parenchyma cells next to the collenchyma layers differentiate into sclerenchyma. As the fruit expands laterally, new vascular bundles continue to differentiate towards the centre of the fruit from the ground parenchyma of the dorsal fruit margin. The area of the fruit margin that is occupied by vascular bundles eventually becomes extensive. The xylem and phloem in the dorsal fruit margin are separated by a cambium. When the pod is mature the cell walls of the parenchymatous mesocarp become thickened and lignified, whereas the collenchymatous stratum becomes partly sclerenchymatous. The zone where the follicle eventually opens is characterised by thick-walled unlignified parenchyma cells between the two ventral bundles at the ventral suture. This unlignified zone is closely connected to the sclerenchymatous flanges of the ventral vascular bundles. The outer epidermis of mature brown pods consists of cells with thick lignified and cutinised walls. The mesophyll of fully developed pods consists of an outer stratum of mesophyll cells with lignified walls and an inner stratum of three or four layers of cells with unlignified walls. The unlignified zone is bordered by a sclerenchymatous stratum that originated from the inner mesophyll layers bordered by another sclerenchymatous stratum that originated from the outer layers of the collenchymatous stratum. The walls of the inner layers of the collenchymatous stratum remain unlignified. Between the sclerenchymatous and non-sclerenchymatous zone of the original collenchyma layers is a transition zone where secondary walls are present but they are unlignified or in various stages of lignification. The inner sclerenchymatous layers of the pericarp probably have a protective function. The inner collenchymatous layers may contribute to fruit opening under dry conditions. The usual method of fruit opening is, however, when the seed forces the fruit valves apart during imbibition.
Acknowledgments
We thank the Department of Agriculture, Northern Province, for permission to do research at the Messina Experimental Farm. We also thank the University of Botswana and Professor M. Lee at the University of the North for the use of EM facilities.
Atkins CA,
Kuo J, Pate JS
(1977) Photosynthetic pod wall of pea (Pisum sativum L.). Plant Physiology 60, 779–786.
Brett, C ,
and
Waldron, K (1990).
Cowan, RS ,
and
Polhill, RM (1981). Detarieae. In ‘Advances in Legume Systematics. Part 1’. pp. 117–135. (Royal Botanic Garden: Kew, UK)
Esau, K (1965).
Fahn, A (1982).
Fahn A, Zohary M
(1955) On the pericarpial structure of the legumen, its evolution and relation to dehiscence. Phytomorphology 5, 99–111.
Ford ES
(1942) Anatomy and histology of the Eureka lemon. Botanical Gazette 104, 288–305.
| Crossref | GoogleScholarGoogle Scholar |
Gunning BES, Pate JS
(1969) ‘Transfer cells.’ Plant cells with wall ingrowths, specialized in relation to short distance transport of solutes—their occurrence, structure and development. The Journal of Cell Biology 37, C7–C12.
| Crossref | GoogleScholarGoogle Scholar |
Jarman PJ, Thomas PI
(1969) Observations on the distribution and survival of mopane (Colophospermum mopane) (Kirk ex Benth.) Kirk ex J.Léonard seeds. Kirkia 7, 103–107.
Jensen, WA (1962).
Jordaan A, Wessels DCJ
(1999) The aril of Colophospermum mopane. Its role during seed germination and fruit opening. South African Journal of Botany 65, 392–397.
Jordaan A,
Wessels DCJ, Kruger H
(2001) Morphology, ontogeny and functional anatomy of the seeds of Colophospermum mopane. South African Journal of Botany 67, 214–229.
Keating, RC (1996). Anther investigations: a review of methods. In ‘The anther. Form, function and phylogeny’. pp. 255–271. (Cambridge University Press: Cambridge)
Mapaure I
(1994) The distribution of Colophospermum mopane (Leguminosae—Caesalpinioideae) in Africa. Kirkia 15, 1–5.
Miller SS,
Bowman LA,
Gijzen M, Miki BLA
(1999) Early development of the seed coat of soybean (Glycine max). Annals of Botany 84, 297–304.
| Crossref | GoogleScholarGoogle Scholar |
Mujambar GP, Preston RD
(1941) The fine structure of collenchyma cells in Heracleum sphondylium L. Royal Society of London. Proceedings Series B 130, 201–217.
O’Brien, TP ,
and
McCully, ME (1981).
Pate JS
(1989) Legume fruits—The structure:function equation. In ‘Advances in legume biology’ (Eds CH Stirton, JL Zarucchi). Monographs in Systematic Botany of the Missouri Botanical Garden 29, 399–415.
Pate, JS ,
and
Kuo, J (1981). Anatomical studies of legume pods—A possible tool in taxonomic research. In ‘Advances in legume systematics. Part 2’. pp. 903–912. (Royal Botanical Gardens: Kew, UK)
Potgieter MJ, Wessels DCJ
(1998) The anatomy and morphology of petioles and leaflets of Hardwickia mopane (Leguminosae: Caesalpinioideae). South African Journal of Botany 64, 281–289.
Roth, I (1977). Fruits of angiosperms. In ‘Encyclopedia of plant anatomy’. (Gebruder, Borntraeger: Berlin)
Warmke HE, Lee SJ
(1977) Improved staining procedures for semithin epoxy sections of plant tissues. Stain Technology 51, 179–185.
Watson, L ,
and
Gunning, BES (1981). Leaf phloem transfer cells in Leguminosae. In ‘Advances in legume systematics’. pp. 717–722. (Royal Botanic Gardens: Kew)
Wessels DCJ,
Potgieter MJ, Jordaan A
(1998) Miraculous mopane for wood, worms and wealth. Recently recognised mopane ecotypes are potentially of great value to farmers. Farmers Weekly, December 25, 50–53.
Wylie RB
(1943) The role of the epidermis in foliar organization and its relation to minor venation. American Journal of Botany 30, 273–280.
