The Evolutionary Potential of Plasticity in Cleistogamy: Exploring Temperature-Induced Variations in Flower Cleistogamy across Soybean ( <i>Glycine max</i> L., Fabaceae) Cultivars

Premise of research. Phenotypic plasticity allows plants to respond developmentally to environmental change. If the extent of trait plasticity has a genetic basis, the degree of plasticity can itself evolve. Furthermore, phenotypes initially induced by the environment can become genetically assimilated, potentially leading to adaptive evolution. This study examines the evolutionary potential of temperature-driven plasticity in cleistogamy (the production of closed, self-pollinating flowers) in soybean (Glycine max L., Fabaceae) by investigating whether different cultivars (genotypes) exhibit variation in their cleistogamous response to ambient temperature. Methodology. A greenhouse experiment was conducted with 9 or 10 replicates of each of 6 soybean cultivars from different maturity groups. The incidence of cleistogamy, defined as the probability that a flower produced by an individual plant will not open at reproductive maturity, was measured under varying temperature conditions. Generalized linear mixed effects models were used to assess the effects of temperature, cultivar, and their interaction on the incidence of cleistogamy. Pivotal results. We found a strong average negative relationship between temperature and the incidence of cleistogamy. However, cultivars varied in their temperature sensitivity: some exhibited a steep response to temperature, while others maintained a relatively more stable incidence of cleistogamy. Conclusions. This study reveals significant genetic variation in the degree of temperature-driven plasticity in cleistogamy in soybean, pointing to the evolutionary potential of plasticity in cleistogamy in flowering plants. Understanding the mechanisms, incidence, and evolvability of plasticity in cleistogamy is relevant for predicting reproductive success of wild and cultivated plants under climate change and warrants further investigation.