Sex expression and breeding strategy in Commelina benghalensis L.

Abstract

This paper describes the results of a series of experiments conducted to unravel the patterns of sex expression and reproductive output in a fascinating species with high variation in sexuality. Commelina benghalensis L., an andromonoecious rainy season weed, bears male and bisexual flowers in axillary spathes of all the plants investigated. Bisexual flowers are of two types; chasmogamous (CH) and cleistogamous (CL). The former are borne on subaerial and the latter on subterranean shoots, in addition to those on aerial spathes. Three populations of the species, designated JU1, JU2 and JU3, were scanned for three consecutive years from 1996 to 1998, and the number and distribution of male, CH and CL flowers per plant were found to vary. The mere number of CH/CL flowers per plant is by itself not an accurate measure of mixed mating. It is necessary to confirm that CH flowers actually outcross and, if they do so, to what extent. Comparison of the pollen/ovule (P/O) ratio and percentage pollen germination on the stigmas of the CH and CL flowers have been used as indices of the pollination system. Confirmation of this was sought from the fruit and seed sets obtained after manual pollination of emasculated flowers with self- and cross-pollen. Results so obtained were compared with those of natural pollination. In the majority of CH flowers, the male and female reproductive phases (i.e. anther dehiscence and stigma receptivity) overlap, providing for self-pollination. However, two exceptions to this general behaviour were found in some plants of all the three populations. In some CH flowers, the female phase matures prior to anther dehiscence while in others, the anthers are sterile. Such plants, designated as variants 1 and 2, respectively, facilitate cross-pollination. While the CL flowers contribute to the production of selfed progeny, the variants of CH ones permit formation of outcrossed progeny, indicating a mixed mating strategy in C. benghalensis.

Seed germination in cleistogamous species: theoretical considerations and a literature survey of experimental results

“…Sabila et al (2012) mechanically scarified aerial and subterranean seeds before testing them for germination and seedling emergence. Kaul and Koul (2009) compared germination of seeds of C. benghalensis derived from open-pollinated, hand self-pollinated, hand cross-pollinated, bagged and emasculated CH (aerial) flowers. Germination ranged from ca 75% (mean for three pollinations dates) for seeds from bagged flowers to >90% (mean for three pollination dates) for those open-and cross-pollinated flowers.…”

Reproductive Assurance through Autogamous Self-pollination across Diverse Sexual and Breeding Systems

“…All the requirements for autogamy are fully met in cleistogamous flowers. The anthers and stigma are in close proximity to each other 2,[19][20][21] . Pollen grains germinate inside the anther or after coming in contact with the stigma following anther dehiscence; pollen tubes enter the stigma and grow through the pistil and release sperm cells in the embryo sac for fertilization.…”

Floral Biology of Fluted Pumpkin (<i>Telfairia occidentalis</i> Hook. F.)

“…Self cleistogamous (pollination before anthesis) chasmogamous (polloination after anthesis). Rarely, both exist in plants, Kaul et al, 2002;Kaul and Koul, 2009 Cross pollination abiotic (wind, water or gravity) or biotic (animals insects). Cucurbits' flowers need insect pollination for successful seed and fruit set.…”

“…Self-pollinated flower (pollination before anthesis) chasmogamous (polloination after anthesis). Rarely, both for instance in Cotnmelina benghalensis 2002; Kaul and Koul, 2009). requires agents which can either be abiotic (wind, water or gravity) or biotic (animals insects).…”