Font Size: a A A

Physiological Traits And Responses To Drought Stress Among Sex Morphs Of Oxyriasinensis(Polygonaceae)

Posted on:2016-05-15Degree:MasterType:Thesis
Country:ChinaCandidate:J YangFull Text:PDF
GTID:2180330503451491Subject:Ecology
Abstract/Summary:PDF Full Text Request
Transition from hermaphrodite to dioecy is one of the most important evolutionary trend in angiosperm. It is generally accepted that dioecious plants occur more frequently in dry and nutrient-poor habitats, suggesting that abiotic stress factors could contribute to evolution of dioecy, which was still poorly supported experimentally. Therefore, experimental examinations on the responses of subdioecious species, a special sexual system comprising male, female, and hermaphrodite plants, to abiotic stress factors could quantify the contribution of abiotic factors on selective pressure on the evolution of dioecy. Oxyria sinensis(Polygonaceae) was reported as dioecious species, but hermaphroditic plants were found in some populations during the field investigations, providing a good material for the evolution of dioecy from hermaphrodite driven by abiotic factors. In order to understand the photosynthetic characteristics of different sex morph, we measured the response curves to light and CO2 of leaves from each sex morph of the transplanted plants of O. sinensis using a LI-COR 6400 XT. We also examined the physiological responses(photosynthesis, nitrogen content, carbon content, carbon isotope compositions and MDHAR) of plants with different sex morphs of O. sinensis, to different water stress. In a glasshouse, male, female, and hermaphrodite plants of O. sinensis were subjected to low, moderate, and high drought stress conditions and lasted 47 days, which was 80%, 50% and 20% of maximum field capacity, respectively. Specific results are as follows:1. The trends of responses to light and CO2 among different sex morphs of O. sinensis were similar, and saturation light intensity of O. sinensis was about 1000 ~ 1200 μmol photons·m-2·s-1. Maximum net photosynthetic rate of male and hermaphrodite plants were higher than female plants but the difference was not significant, indicating that the photosynthetic capacity of male plants might be higher than female plants to some degree. The light compensation point and the dark respiratory rate of female plants were the lowest among different sex morphs of O. sinensis, so female plants might be well adaptive to weak light, and the metabolism of female plants was slower than others. In high CO2 condition, net photosynthetic rate of male plants was the highest and female plants was the lowest, and no stomatal limitation was found among different sex morphs of O. sinensis.2. Most of photosynthetic parameters(Pmax, Gs, E, WUEi, Fv/Fm, Ls) were significantly different among different water condition in each sex morph, suggested that water availability could influence the photosynthesis of O. sinensis. Specifically, among different water conditions, eight parameters(except C%, WUEi, Fv/Fm) of male plants were significantly different, and only 2(Pmax, δ13C) and 3(Gs, δ13C, MDHAR) of female and hermaphrodite plants were significantly different, indicating that male plants could respond quickly to the environmental changes. Nitrogen-use efficiency and nitrogen content was affected significantly by sex morph but not by water availability and their interaction. When plants of O. sinensis were subjected to the lowest water condition, the nitrogen-use efficiency of male and female plants were higher than hermaphrodite plants significantly, and nitrogen content of male and female plants were lower than hermaphrodite plants significantly. The activity of MDHAR of male plants was the highest among the sex morphs, and the activity of MDHAR was affected by sex morph and interaction between sex morph and water condition.Conclusively, female plants of O. sinensis could survive well in weak light, because the lowest Pn, Rd and Φi of female plants were found among sex morph. There were no significant difference in most of the measured parameters among the sex morphs under each drought stress treatment, indicating that O. sinensis might be well adapted to drought stress conditions as its typical habitat is the dry and hot habitats of xerothermic river valleys; Additionally, the nitrogen-use efficiency of male and female plants are higher than hermaphrodite plants significantly, and the nitrogen content(%) of male and female plants are lower than hermaphrodite plants significantly, and the activity of MDHAR of male plant were higher than hermaphrodite plants significantly under conditions of drought stress, which might have contributed to the evolution of dioecy from the hermaphrodite to some degree.
Keywords/Search Tags:Oxyria sinensis, hermaphrodite, dioecy, evolutionary transition, photosynthesis, drought stres, response
PDF Full Text Request
Related items