Effects Of Light And Pollination Environment On The Growth And Reproductive Characteristics Of Sagittaria Trifolia L.

In the process of growth and reproduction,plants are inevitably affected by the external environment and individual's specific genotype.The effect of the external environment may be greater than genotype on plants' performance.The ubiquity of natural habitat heterogeneity makes it difficult for plants to obtain and utilize resources,which can have a profound impact on their growth,reproduction and dispersal.The habitat in which a plant is located is the sum of the abiotic factors and biological factors around it.When the resources or mates required by plants are limited,they must respond to changes in various factors in the environment by utilizing and allocating resources among various functions and structures in order to complete life history and successfully reproduce offspring.This study uses Sagittaria trifolia as the research material.Using a comparative experimental setting,and enlightened by light variances in natural populations of Sagittaria trifolia,we simulated two kinds of light environments:full sunlight open area without any shelter and understory area under the shade of naturally occurring trees and tall shrubs.At the same time,with a similar light intensity to the understory area,a netting area covered with a bridal-veil net was established in order to preclude flying insects and simulate a habitat of limited pollinators.The effects of both abiotic factors and biological factors on plants'morphological and reproductive characteristics were observed for three consecutive years.The results showed that the vegetative growth of Sagittaria trifolia was affected by light environment.When plants were in the understory area,they showed increased plant height,probably to compete for sunlight.Plants promoted resource investment to sexual reproductive organs under open area,which was 2-3 times higher than the understory area,in aspects of total number of inflorescences,female flowers,male flowers and total flowers.Open environment also elevated plants' fruit set,total fruit number,and seed number.The lack of light in understory area has also led to an increase in plants'investment to bulbil size.On the other hand,biological factors also affected the sexual reproduction of Sagittaria trifolia,which increased the total number of inflorescences,female flowers,male flowers and total flowers in the pollinator-limited environment.Such changes could be a response by plants to pollen limitation and reproductive deficiency,in order to extend flowering duration and attract more pollinators.The limitation of pollinators led to a decrease in fruit set,number of seeds per fruit,and average seed size.Biological factors also influenced plants' asexual reproduction.In the pollinator-limited environment,the number of bulbils was increased.Above results indicated that sufficient light had a positive effect on sexual reproductive organs and performances,whereas under limited light,plants increased height and the size of asexual reproduction to improve reproductive fitness.In a pollinator-limited environment,plants tended to assure future generations by increasing the number of inflorescences,flowers,and bulbils.This study emphasized the quantification of plant vegetative growth,sexual and asexual reproduction and found that both abiotic and biological factors played important roles in the plant morphological characteristics and reproductive patterns.Whenever light or pollinator is limited,plants of Sagittaria trifolia are capable of responding to environmental factors quickly,adopting certain reproductive strategies,and allocating resources thereby maximizing the overall fitness.The results of this research have deepened our understanding of the effect of environmental heterogeneity on plant growth and reproduction.in particular,how resources and pollination,the two major limiting factors in the process of plant propagation,have shaped plants and their reproductive responses in turn.