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1.
Spencer C. H. Barrett 《Philosophical transactions of the Royal Society of London. Series B, Biological sciences》2010,365(1537):99-109
Flowering plants display spectacular floral diversity and a bewildering array of reproductive adaptations that promote mating, particularly outbreeding. A striking feature of this diversity is that related species often differ in pollination and mating systems, and intraspecific variation in sexual traits is not unusual, especially among herbaceous plants. This variation provides opportunities for evolutionary biologists to link micro-evolutionary processes to the macro-evolutionary patterns that are evident within lineages. Here, I provide some personal reflections on recent progress in our understanding of the ecology and evolution of plant reproductive diversity. I begin with a brief historical sketch of the major developments in this field and then focus on three of the most significant evolutionary transitions in the reproductive biology of flowering plants: the pathway from outcrossing to predominant self-fertilization, the origin of separate sexes (females and males) from hermaphroditism and the shift from animal pollination to wind pollination. For each evolutionary transition, I consider what we have discovered and some of the problems that still remain unsolved. I conclude by discussing how new approaches might influence future research in plant reproductive biology. 相似文献
2.
Lee D. Thomas 《Behavioural processes》2009,81(2):264-269
Four pigeons responded under a progressive-delay procedure. In a signaled-delay condition, a chained variable interval (VI) 30-s progressive time (PT) 4-s schedule was arranged; in an unsignaled-delay condition, a tandem VI 30-s PT 4-s schedule was arranged. Two pigeons experienced a signaled-unsignaled-signaled sequence; whereas, two pigeons experienced an unsignaled-signaled-unsignaled sequence. Effects of saline and d-amphetamine were determined under each condition. At intermediate doses (1.0 and 1.78 m/kg) delay functions were shallower, area under the curve was increased, and, when possible, break points were increased compared to saline; these effects were not systematically related to signaling conditions. These effects on control by delay often were accompanied by decreased response rates at 0 s. These results suggest that stimulus conditions associated with the delay may not play a crucial role in effects of d-amphetamine and other stimulants on behavior controlled by reinforcement delay. 相似文献
3.
The involvement of gibberellins in the control of flowering of sunflower was studied by direct application of GA3 to the apex of the plants, analysis of the endogenous levels of gibberellin-like substances at different plant ages, and indirectly by the application of paclobutrazol, an inhibitor of gibberellin synthesis. GA3 speeded-up flower initiation and floral apex development. The time of GA3 application was more critical than the amount of GA3 applied. The endogenous levels of gibberellin-like compounds increased significantly by day 15 after sowing. The application of paclobutrazol markedly delayed floral initiation and this effect was also depedent on plant age. Both GA3 and paclobutrazol had their greatest effects between 10 and 20 days after sowing suggesting that an increase in gibberellins in that time period plays a role in floral initiation. 相似文献
4.
Despite similar ecology, mating systems and female preferences for supernormal tails, the 17 species of African widowbirds and bishops (Euplectes spp.) show astonishing variation in male tail ornamentation. Whereas bishops retain their brown nonbreeding tails in nuptial plumage, widowbirds grow black nuptial tails, varying in length from a few centimetres in E. axillaris to the extreme half metre train of E. progne. Here, we phylogenetically reconstruct the evolution of the discrete trait, nuptial tail and the continuous trait, tail length, using a molecular phylogeny of 33 Euplectes subspecies. Unlike many recent findings of labile evolution of plumage ornaments, our results suggest that the nuptial tail of Euplectes is a derived and phylogenetically conserved ornamental trait that, once gained, shows directional evolution in its expression. Directionality is demonstrated in the trivial sense of a short‐tailed ancestor, and by contingency and randomization tests suggesting that branches with increasing tail length are overrepresented. This supports an early origin and strong retention of directional female mate choice in widowbirds and bishops, as previously indicated by empirical and experimental results, and provides a less labile, yet rapid scenario of sexually selected diversification. 相似文献
5.
6.
Sara Basconsuelo Herminda Reinoso Eugenia Lorenzo Rubén Bottini 《Plant Growth Regulation》1995,16(2):113-119
Morphological studies were carried out with peach flower buds collected monthly in 1989 and 1990, from two months before leaf fall (7 March) until two to three weeks before bloom (7/8 August). Chilled (2–4°C for 30 days) and unchilled buds were exposed to 20 to 25°C, 100% RH and continuous light. Gibberellin A3 (3 ng or 30 ng) was applied to some of the non-chilled cuttings at three days intervals. Then, 12, 19, and 26 days after they were planted, the buds were sampled and processed for histological studies. Cultured flower buds (chilled or unchilled) had accelerated anther and gynoecium morphogenesis after 12 days under controlled conditions, compared to buds processed immediately after collection from the field. Chilling treatment augmented the bud culture effect, while Gibberellin A3 applications to the excised buds retarded bud morphogenesis to a stage comparable to that of buds collected directly from the field. This, suggests that the comparatively high levels of Gibberellin A1/3 we previously found in mid winter [15, 18] could be at least one of the factors that controls floral bud dormancy by retarding anther and gynoecium development. 相似文献
7.
Floral determination in the terminal bud of the short-day plant Nicotiana tabacum cv. Maryland Mammoth has been investigated. Plants grown continuously in short days flowered after producing 31.4±1.6 (SD) nodes while plants grown continuously in long days did not flower and produced 172.5±9.5 nodes after one year. At various ages, expressed as number of leaves that were at least 1.0 cm in length above the most basal 10-cm leaf, one of three treatments was performed on plants grown from seed in short days: 1) whole plants were shifted from short days to long days, 2) the terminal bud was removed and then rooted and grown in long days, and 3) the terminal bud was removed and then rooted and grown in short days. Whole plants flowered only when shifted from short days to long days at age 15 or later. Only rooted terminal buds from plants at age 15 or older produced plants that flowered when grown in long days. Only terminal buds from plants at age 15 or older that were rooted and grown in short days produced the same number of nodes as they would have produced in their original locations while buds from younger plants produced more nodes than they would have in their original locations. Thus, determination for floral development in the terminal bud, as assayed by rooting, is simultaneous with the commitment to flowering as assayed by shifting whole plants to non-inductive conditions.Abbreviations LD
long day(s)
- SD
short day(s)
- DN
dayneutral 相似文献
8.
In the last twenty-five years, young inflorescences, floral buds and individual floral organs of a number of species have been cultured in vitro. There is considerable variability in the requirement of plant growth regulators and nutritional factors for flower development of different species. This variability is compounded by the fact that the hormonal and nutritional requirements are different at various stages of organ and floral development. Experimental studies on normal and mutant flowers in vitro have provided insights into some of the regulatory processes in floral organogenesis. The potential use of the in vitro technique in elucidating the various mechanisms in flower development is stressed. 相似文献
9.
Studies were undertaken with Brassica napus L. cv. Topas to identify buds containing microspores predisposed to embryogenesis in vitro and to investigate bud and microspore development in relation to this process. No significant correlation was found between the final embryo number and bud components. There appears to be a developmental window of less than 8 h duration during which microspores are very likely to form embryos: over 70% of the microspores can undergo division and up to 70% of these can form embryos. Embryos were mainly obtained from late uninuucleate to early binucleate microspores: the former contained mainly a G2 or M phase nucleus located at the microspore periphery and the latter a generative nucleus (associated with the intine) and a vegetative nucleus. Observations indicated that only the vegetative nucleus contributed to embryo formation. The first embryogenic division occurred between 8 and 16 h for uninucleate- and between 8 and 48 h for binucleate-derived embryos. 相似文献
10.