Reproductive Strategy Of Wetland Plant Iris Laevigata

Plant reproduction strategies are a key topic in plant ecology,and are of great importance for the individual fitness and the continuation of a species.Environmental conditions are the main factors that shape plant reproduction strategies.Compared with extreme habitats such as deserts and high mountains that have always been concerned by scholars,the environmental fluctuation characteristics of wetland ecosystems are more obvious.The reproduction strategy of wetland plants is the result of long-term adaptation to fluctuating environments.Hence,studying the reproductive strategies in wetland plants provides a great opportunity for a comprehensive understanding of the plant's response to changing environmental conditions during the succession of ecosystems.It will not only help to understand the plant reproductive strategies but will also aid in our understanding of how climate change may affect biodiversity,a topic that is of great importance currently.This work takes the widely distributed Iris laevigata in Jinchuan Wetland,Gushantun Wetland and Hanlongwan Wetland of Longwan National Nature Reserve in Jilin as the research object.It uses in-situ field observation,micro-region simulation and indoor controlled experiments to investigate the trade-off between sexual reproduction and asexual reproduction.Using these approaches,this study includes an in-depth investigation of sexual expression pattern,reproduction assurance strategy,and the profile of volatile release during sexual reproduction.The specific research work is as following:1.Exploring the trade-off relationship between sexual reproduction and asexual reproduction of Iris laevigata.There are two morphologically distinct ramate types in I.laevigata�sexual and asexual rametes,which respectively achieve the sexual and asexual reproduction of the plant.In this experiment,two kinds of ramates are used as research objects.Through field experiments and indoor control experiments,the resource allocation mode is explored,and the morphological differentiation,division of labor and cooperation in physiological functions are revealed.The results showed that the density of asexual ramate was significantly higher than that of sexual ramate,the plant height was large,the aerial part had only leaves,and the biomass was significantly smaller than that of sexual ramate.Physiologically,asexual ramate only grow vegetatively,and photosynthetic efficiency is significantly higher than that of sexual ramate.Sexual ramate can be sexually propagated through seed production,but individuals who fail to pollinate will quickly wither.This indicates that the division of physiological functions of the two species is specific and irreversible.After ¹⁵N labeling of asexual clones,?¹⁵N values of sexual ramate in the experimental group was significantly higher than the control group,indicating the cooperation of the physiological functions of the two varieties.Based on the above research results,the social division of labor theory of clonal plants is proposed:the cloned plant is a social plant,and the differentiation of sexual clones into"breeders"constitutes a very small number of reproductive roles,responsible for the production of sexual offspring;and The differentiation of a large number of asexual clones into"workers"constitutes a labor role,responsible for the acquisition and supply of nutrients.This division of labor model strengthens the ability of divisions to perform division of labor.Both division of labor and cooperation ensure the survival and reproduction of I.laevigata.It also theoretically explains the trade-off mechanism between sexual reproduction and asexual reproduction.2.Further exploration of the sexual reproduction of the I.laevigata of the wetland plant,and the response of flower characteristics and gender expression to the wetland hydrological disturbance.This study combined the wetland water levels from 2013 to2015 to make longitudinal and horizontal comparisons of the I.laevigata flower characteristics and sexual system expression processes in three wetlands,and verified by micro-area simulation.The results showed that the water level of the Hanlong Bay wetland in 2013 was significantly higher than in 2014 and 2015,and significantly higher than the other two wetlands.In 2009,9.09%of the I.laevigata in the Hanlong Bay Wetland failed to produce pollen.In 2014 and 2015,the pollen was successfully produced after the water level returned to normal;the other two wetlands successfully produced pollen from 2013 to 2015.The two-factor analysis of variance showed that the flower size,anther length,and pollen number of Hanlong Bay Wetland in 2013 were significantly smaller than those in 2014 to 2015 and smaller than the other two wetlands.In addition,the seed weights of Hanlong Bay Wetland in 2014 and 2015 were significantly higher than in 2013 and also higher than the other two wetlands,but the ovary length,ovule number and seed number were not significantly different in different wetlands and years.Among the 8 Chinese-style water level control tanks simulated in the micro area,the male function of the I.laevigata appeared to decline in the high water level group.It can be seen that under high water stress in the wetland,the expression of male functions in the bisexual flowers of the I.laevigata is inhibited,and the female flower is transformed into a female flower,which results in the sexual system of the I.laevigata changing from an bisexual flower to a hermaphrodite,and the seed quantity and quality are reduced.This part of the study is helpful to understand the evolution of the sexual system of plants under environmental stress,and to reveal the potential impact of climate change on biodiversity.3.In the study of sexual reproduction,it was found that the process of corolla fading of the I.laevigata is quite special--rotating shedding,which leads to the contact between male and female organs.This may be a reproductive strategy to adapt to such a volatile wetland ecosystem by delaying self-crossing.This study measured the pollen vigor,stigma receptivity,petal length,anther and distance between stigma at different flowering stages of I.laevigata,and different pollination treatments were performed to determine the fruit setting rate,seed quantity and quality,and countermeasures for its reproduction.Explore.The results showed that the petals began to rotate on the third day after flowering,and the distance between the anther and the stigma also gradually decreased.At the same time,the pollen still retains its pollen activity during the decline period,and the stigma is highly receptive,providing the necessary conditions for delayed selfing.In the pollination experiment,it was found that the self-selfing group can achieve a fruit set rate of 10%,while the fruit set rate is 0%when the petals are removed,indicating that the I.laevigata has delayed selfing,and the"rotating"movement of the petals in the fading period is responsible for the delayed self-setting.However,compared to natural pollination,the number of seeds and the quality of individual seeds obtained by delayed selfing were significantly reduced.In addition,under natural conditions,the pollen output on rainy days decreased significantly,less than one fifth of that on sunny days.Compared with the pollen output,the fruit setting rate is relatively less affected by the weather.The fruit setting rate on sunny days reaches 64.3%�5.64%.Although the fruit setting rate on rainy days has also decreased significantly,it can also reach 38.8%�0.05%.In summary,the I.laevigata has a countermeasure for delayed selfing through the"rotary"movement of the corolla,which provides a delay guarantee.Future climate change may lead to changes in pollinator structure or extreme climatic conditions.This delayed selfing strategy can provide a guarantee for the successful sexual reproduction of I.laevigata s,and has a more selective advantage than species that do not have delayed selfing.4.In the course of the study,the Calliteara pudibunda erupted in Jinchuan wetland in2018,and a large number of leaves and flowers of wetland plants such as sedge and reed were ate,while I.laevigata were rarely ate.Through observation,it does not have the common physical defense mechanism such as needles,but the sensory difference of different parts of the flower and the flowering plant is significant.To study this,solid phase microextraction and gas chromatography-mass spectrometry?GC/MS?techniques are used to determine the volatile odor components and their relative contents of swallows in time?flowers of different flowering periods?and in space?different parts of flowering periods?.At the same time,I also observed and recorded the activities of pollinators and planters.GC/MS analysis results showed that the average composition of the aroma components of the I.laevigata was 13 compounds,20 compounds were at the flowering stage,and 12 compounds were at the decline stage.The flower bud and the senescing flowers were mainly composed of phytoprotectants?e.g.linalool and eucalyptus oil?,and the active flowering period is dominated by compounds that attract pollinators?e.g.cis-ocalene,d-limonene?.Linalool is the only volatile substance that was present in all three flowering periods,and its relative content changes are also the most obvious.The three periods are 0.06%,0.57%,and 40.38%,respectively.Volatile compounds contained in various parts of the I.laevigata during full bloom are as follows:20 in flowers,12 in ovary,12 in leaves,4 in flower stems,and 4 in flower stem secretions.Among them,in addition to flowers and flower stems,they contain a large number of defensive volatiles,such as the relative content of eucalyptus oil in flower stem secretions is 46.57%,in leaves is 34.64%,in ovary is8.54%,in flowers is only 1.72%.The effective pollinator of the I.laevigata is the bumblebee family.The frequency of flower visits is 2.47 times/day/flower.The length of a single flower visit is 8.82 seconds.There is no pollen restriction on the I.laevigata.I.laevigata phytophagous includes the Calliteara pudibunda and Apodemus peninsulae.Only 3.4%of the I.laevigata are fed by Calliteara pudibunda,but 85.67%of the sexual ramates of I.laevigata's flowers are fed by Apodemus peninsulae.In summary,the spatiotemporal regulation of the volatile components of the I.laevigata has an adaptive evolutionary meaning that defends insects from planters and attracts pollinators.This thesis contains a series of studies on breeding strategies of I.laevigata in the wetland ecosystem.Results here have enriched our understanding of plant reproductive strategies,and the impact of global climate change on the level of biodiversity from the perspective of plant reproduction processes.