The reproductive biology of Cornus capitata was studied in detail from June 2014 to October 2015 in Tehri Garhwal, Uttarakhand, western Himalaya, India and elucidated floral morphology, confirming autogamy, geitonogam...The reproductive biology of Cornus capitata was studied in detail from June 2014 to October 2015 in Tehri Garhwal, Uttarakhand, western Himalaya, India and elucidated floral morphology, confirming autogamy, geitonogamy, and xenogamy. A new inflorescence ball formed each year with developing fruits that were initiated the previous year; thus reproduction is a continuous cycle. The total pollen production within a tree ranged between 4.0 × 10~7 and 9.3 × 10~7. Anthesis peaked between 08:00 and 10:00. There was significant effect of micro-environmental condition on anthesis(F = 243.8, p = 3.01). A significant positive relationship between the number of lateral shoots and total inflorescence showed that the inflorescence production in C. capitate depends largely on the number of lateral shoots. Time and concentration of various solutions significantly affected pollen germination(time: F = 5.39, p = 0.002; concentration: F = 1.40,p = 0.234). Anthophora bees and thrips were observed as the main pollinators. There was a significant difference in seed set between natural and obligate self-pollination(t = 11.84, p = 1.99). Significant effect was also observed on fruit size(t = 8.88, p = 2.09) between open and shaded conditions. SEM micrographs of pollen grains showed that the shape of dehydrated pollen grains differed greatly due to variations in the rate of dehydration among pollen grains within the anther. Seed germination was observed only in quality seed derived from open pollination, supporting xenogamy in C. capitata. Findings of the present study will be of immense value in formulating effective conservation measures for the species in wild habitats.展开更多
Male components of the reproduction process in Pinus roxburghii were investigated for their variation in time and space as well as pollination, viz. flowering phenology, pollen production variability and pollen disper...Male components of the reproduction process in Pinus roxburghii were investigated for their variation in time and space as well as pollination, viz. flowering phenology, pollen production variability and pollen dispersal, for five successive years at two different locations （at the lower and higher elevations）. The study reveals that elevation and the hour of the day are the main determi- nants of anthesis and microsporangium dehiscence, because both are related to temperature and humidity. The receptivity of ovulate cone strobili or female strobili occurred earlier at the lower elevation than at the higher elevation, with a longer receptivity period in the latter case. The phenology of male and female cones varied significantly between years and elevations. The determinations of pol- len yield considered various sources of variability, i.e., the number of pollen strobili per branch, strobili per tree, microsporangia per tree and pollen grains per tree. Each of these parameters revealed significant year-to-year and elevation effects. Year-to-year varia- tion in the production of pollen cone and pollen grains with mass production after a three-year period revealed a three-year cycle of masting in pollen production in P. roxburghii. The pollen dispersal decreased quickly with distance from the pollen source. As a con- sequence, a distance of 600 m was proposed as a minimum to prevent contamination by pollen in the management of seed orchards. The results ultimately suggest that the ample production of pollen grains per tree along with flowering synchrony and long dispersal of pollen grains results in homogeneity in large populations.展开更多
Background:The expression of gender in gymnosperms is challenging because the extent of variability in gender segregations in tree crowns and selection pressure of nature can modify the gender through time.Methods:An ...Background:The expression of gender in gymnosperms is challenging because the extent of variability in gender segregations in tree crowns and selection pressure of nature can modify the gender through time.Methods:An in-depth investigation on spatial segregation of genders in tree crowns and sex expression of a total of 500 trees in five different natural populations of Cedrus deodara was carried out and verified the occurrence of subdioecious(co-existence of male,female,and monoecious)genders in C.deodara.Results:Five different sexual morphs were apparent among the 500 selected individuals as(1)pure male(M):bearing only male strobili in the whole crown with 22.2%;(2)pure female(F):bearing only female strobili in the whole crown with 12.4%;(3)mixed-monoecious(MM):bearing both male and female strobili with 13.6%;(4)predominantly female(PF)with 25.6%;and(5)predominantly male(PM)with 26.2%.The occurrence of multiple sexual morphs resulted from the complex selection pressure,which increased the stability of the populations.The segregation of genders in crown layers deemed to increase the fitness that may be a mechanism for accelerating outcrossing.The results of the study suggest that the subdioecious gender expression in C.deodara is evolved through the monoecy–paradioecy pathway.The production of male strobili revealed non-significant effect of tree sizes whereas a significant effect was observed for the production of female strobili.Our study established that the total pollen and seed outputs in C.deodara changed frequently according to gender expression.Conclusions:The size of the tree,resource availability,sex allocation,plant architecture,gender segregation in crowns,and habitat conditions are the prominent causes for gender plasticity.展开更多
Background:The ability to produce seeds when pollinators or potential mates are scarce is one of the principal advantages of self-pollination in flowering plants.However,the role of pollinators mediating self-pollinat...Background:The ability to produce seeds when pollinators or potential mates are scarce is one of the principal advantages of self-pollination in flowering plants.However,the role of pollinators mediating self-pollination to ensure seed set when pollen or potential mates are limited has received less attention.This study examined the reproductive consequences and involvement of pollinators in assuring seed set in an isolated tree of Magnolia grandiflora,a predominantly outcrossing species.Methods:We tested various aspects of reproduction such as flower density,floral rewards,stigma receptivity,pollinator abundance and behaviour,fruit set and seed set,in two successive reproductive years(2015-2016).Results:Flowers of M.grandiflora possess a suite of traits facilitating pollinator-mediated self-pollination(PMS),although the chances of autonomous self-pollination are reduced due to herkogamy,spatial separation of anther and stigma.The mean pollen production/flower was 5,152,289±285,094 with a pollen-to-ovule ratio of 39430±164.We found a significant positive correlation between number of visits and seed production for bees(r=0.5099,p=0.0007)and beetles(r=0.7159,p=0.00001),indicating these are effective at PMS.There was a significant negative correlation for thrips(r=-0.3206,p=0.044)and no correlation for flies or spiders.The percent fruit set was 100%and the seed set per ovule ranged between 19 and 20%.Conclusions:PMS will guarantee reproductive assurance and mitigate the effect of reduced mates or pollen limitation which is expected to increase the fecundity and establishment of individual trees in geographically isolated locations.展开更多
基金supported by the grant from Department of Biotechnology,Government of India,New Delhi
文摘The reproductive biology of Cornus capitata was studied in detail from June 2014 to October 2015 in Tehri Garhwal, Uttarakhand, western Himalaya, India and elucidated floral morphology, confirming autogamy, geitonogamy, and xenogamy. A new inflorescence ball formed each year with developing fruits that were initiated the previous year; thus reproduction is a continuous cycle. The total pollen production within a tree ranged between 4.0 × 10~7 and 9.3 × 10~7. Anthesis peaked between 08:00 and 10:00. There was significant effect of micro-environmental condition on anthesis(F = 243.8, p = 3.01). A significant positive relationship between the number of lateral shoots and total inflorescence showed that the inflorescence production in C. capitate depends largely on the number of lateral shoots. Time and concentration of various solutions significantly affected pollen germination(time: F = 5.39, p = 0.002; concentration: F = 1.40,p = 0.234). Anthophora bees and thrips were observed as the main pollinators. There was a significant difference in seed set between natural and obligate self-pollination(t = 11.84, p = 1.99). Significant effect was also observed on fruit size(t = 8.88, p = 2.09) between open and shaded conditions. SEM micrographs of pollen grains showed that the shape of dehydrated pollen grains differed greatly due to variations in the rate of dehydration among pollen grains within the anther. Seed germination was observed only in quality seed derived from open pollination, supporting xenogamy in C. capitata. Findings of the present study will be of immense value in formulating effective conservation measures for the species in wild habitats.
文摘Male components of the reproduction process in Pinus roxburghii were investigated for their variation in time and space as well as pollination, viz. flowering phenology, pollen production variability and pollen dispersal, for five successive years at two different locations （at the lower and higher elevations）. The study reveals that elevation and the hour of the day are the main determi- nants of anthesis and microsporangium dehiscence, because both are related to temperature and humidity. The receptivity of ovulate cone strobili or female strobili occurred earlier at the lower elevation than at the higher elevation, with a longer receptivity period in the latter case. The phenology of male and female cones varied significantly between years and elevations. The determinations of pol- len yield considered various sources of variability, i.e., the number of pollen strobili per branch, strobili per tree, microsporangia per tree and pollen grains per tree. Each of these parameters revealed significant year-to-year and elevation effects. Year-to-year varia- tion in the production of pollen cone and pollen grains with mass production after a three-year period revealed a three-year cycle of masting in pollen production in P. roxburghii. The pollen dispersal decreased quickly with distance from the pollen source. As a con- sequence, a distance of 600 m was proposed as a minimum to prevent contamination by pollen in the management of seed orchards. The results ultimately suggest that the ample production of pollen grains per tree along with flowering synchrony and long dispersal of pollen grains results in homogeneity in large populations.
文摘Background:The expression of gender in gymnosperms is challenging because the extent of variability in gender segregations in tree crowns and selection pressure of nature can modify the gender through time.Methods:An in-depth investigation on spatial segregation of genders in tree crowns and sex expression of a total of 500 trees in five different natural populations of Cedrus deodara was carried out and verified the occurrence of subdioecious(co-existence of male,female,and monoecious)genders in C.deodara.Results:Five different sexual morphs were apparent among the 500 selected individuals as(1)pure male(M):bearing only male strobili in the whole crown with 22.2%;(2)pure female(F):bearing only female strobili in the whole crown with 12.4%;(3)mixed-monoecious(MM):bearing both male and female strobili with 13.6%;(4)predominantly female(PF)with 25.6%;and(5)predominantly male(PM)with 26.2%.The occurrence of multiple sexual morphs resulted from the complex selection pressure,which increased the stability of the populations.The segregation of genders in crown layers deemed to increase the fitness that may be a mechanism for accelerating outcrossing.The results of the study suggest that the subdioecious gender expression in C.deodara is evolved through the monoecy–paradioecy pathway.The production of male strobili revealed non-significant effect of tree sizes whereas a significant effect was observed for the production of female strobili.Our study established that the total pollen and seed outputs in C.deodara changed frequently according to gender expression.Conclusions:The size of the tree,resource availability,sex allocation,plant architecture,gender segregation in crowns,and habitat conditions are the prominent causes for gender plasticity.
基金One of the authors VPK is thankful to Department of Biotechnology(DBT),New Delhi,for financial assistance.
文摘Background:The ability to produce seeds when pollinators or potential mates are scarce is one of the principal advantages of self-pollination in flowering plants.However,the role of pollinators mediating self-pollination to ensure seed set when pollen or potential mates are limited has received less attention.This study examined the reproductive consequences and involvement of pollinators in assuring seed set in an isolated tree of Magnolia grandiflora,a predominantly outcrossing species.Methods:We tested various aspects of reproduction such as flower density,floral rewards,stigma receptivity,pollinator abundance and behaviour,fruit set and seed set,in two successive reproductive years(2015-2016).Results:Flowers of M.grandiflora possess a suite of traits facilitating pollinator-mediated self-pollination(PMS),although the chances of autonomous self-pollination are reduced due to herkogamy,spatial separation of anther and stigma.The mean pollen production/flower was 5,152,289±285,094 with a pollen-to-ovule ratio of 39430±164.We found a significant positive correlation between number of visits and seed production for bees(r=0.5099,p=0.0007)and beetles(r=0.7159,p=0.00001),indicating these are effective at PMS.There was a significant negative correlation for thrips(r=-0.3206,p=0.044)and no correlation for flies or spiders.The percent fruit set was 100%and the seed set per ovule ranged between 19 and 20%.Conclusions:PMS will guarantee reproductive assurance and mitigate the effect of reduced mates or pollen limitation which is expected to increase the fecundity and establishment of individual trees in geographically isolated locations.
