Abstract
Seed morph, abiotic conditions and time of germination can affect plant fitness, but few studies have tested their combined effects on plasticity of plant life history traits. Thus, we tested the hypothesis that seed morph, germination season and watering regime influence phenotypic expression of post-germination life history traits in the diaspore-heteromorphic cold desert winter annual/spring ephemeral Diptychocarpus strictus. The two seed morphs were sown in watered and non-watered plots in late summer, and plants derived from them were watered or not-watered throughout the study. Seed morph did not affect phenology, growth and morphology, survival, dry mass accumulation and allocation or silique and seed production. Seeds in watered plots germinated in autumn (AW) and spring (SW) but only in spring for non-watered plots (SNW). A high percentage of AW, SW and SNW plants survived and reproduced, but flowering date and flowering period of autumn- vs. spring-germinated plants differed. Dry mass also differed with germination season/watering regime (AW > SW > SNW). Number of siliques and seeds increased with plant size (AW > SW > SNW), whereas percent dry mass allocated to reproduction was higher in small plants: SNW > SW > AW. Thus, although seed morph did not affect the expression of life history traits, germination season and watering regime significantly affected phenology, plant size and accumulation and allocation of biomass to reproduction. Flexibility throughout the life cycle of D. strictus is an adaptation to the variation in timing and amount of rainfall in its cold desert habitat.
Highlights
Plants that germinate at different seasons are subjected to different biotic and abiotic environmental conditions, which may have consequences on the life cycle
We hypothesized that (1) plants derived from different seed morphs that germinate in the same season or under the same watering regimes would differ in life history traits, and (2) germination season and watering regime would affect the expression of plasticity in the major life history traits
Our first hypothesis that plants derived from the two seed morphs that germinate in the same season or under the same watering schedule would differ in life history traits was not supported
Summary
Plants that germinate at different seasons are subjected to different biotic and abiotic environmental conditions, which may have consequences on the life cycle. Plants from seeds that germinate in late summer or autumn overwinter as rosettes, are vernalized during winter and flower, set fruit and die the following summer; they behave as winter annuals. Plants from seeds that germinate in spring grow during summer, are vernalized during winter and flower, set fruit and die the second summer; they behave as strict biennials. The two or more seed morphs have different dormancy/germination behaviors and give rise to plants that differ in life history characteristics [5]. Seed heteromorphism may allow escape from the negative effects of sib competition [8] and reduce the risk of failure under temporal environmental uncertainty [9]
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