Phenotypic plasticity in response to seasonal light regimes in Smilacina stellata, (Liliaceae), from three wetland habitats: An ontogenetic perspective.

摘要

Phenotypic plasticity is a critical form of adaptation for plants that live in changing environments. However, a plant's sensitivity to the environment may change throughout development constraining plasticity. In addition, phenotypes may reflect "historical effects," the environmental conditions that a plant experienced in a previous growing season. For plants that preform their organs, historical effects may particularly constrain plasticity; phenotypes may reflect previous environmental conditions.; I investigated developmental constraints on plasticity in Smilacina stellata (Liliaceae) in forested fens, floodplains, and open fens where S. stellata experiences three different seasonal light regimes. S. stellata preforms its organs under one light environment, yet these organs emerge the following growing season under a different light environment.; I conducted field and greenhouse studies and measured biomass allocation, physiology and morphology for traits known to be influenced by light on plants in each habitat. I addressed three questions: (1){A0}Do past developmental events of organ preformation constrain S. stellata's ability to respond to the current light environment? (2){A0}Can plants respond to the changing light regime throughout their seasonal development? (3){A0}Do past environments influence current phenotypes?; Field light manipulations demonstrated that organ preformation did not constrain S. stellata's responses to early season light. Plants were able to respond to manipulated light levels throughout the growing season. These results differed from the field observations where plants did not respond to the seasonally changing light regime. It appears that the ability of plants to respond throughout their seasonal development is dependent upon light quantity.; Greenhouse and field experiments revealed that several factors influence plasticity in S. stellata. Previous environments influenced S. stellata phenotypes; plants that formed their organs under field conditions showed differences in biomass allocation, morphology and physiology as compared to plants that formed their organs under greenhouse conditions. In addition, very low light levels stimulated a different suite of responses than low light levels; the magnitude and direction of plasticity in S. stellata depends on light level. Habitat-level variation for plasticity in S. stellata suggested that the light environments in each habitat have selected for different sensitivities to light.