Comparison of environmental and mutational variation in flowering time in Arabidopsis

Developmental dynamics can be influenced by external and endogenousfactors in a more or less analogous manner. To compare the phenotypiceffects of (i) environmental [i.e. standard (stPhP) and extended(exPhP) photoperiods] changes in Arabidopsis wild types and(ii) endogenous genetic variation in eav1–eav61 earlyflowering mutants, two temporal indicators were analysed, thetime to bolting (DtB) and the number of leaves (TLN). It wasfound that DtB and TLN are differentially affected in differentenvironmental and genetic contexts, and some factors of dynamicconvergence were identified. The quantitative response to photoperiodis markedly contingent on the phototrophic input for DtB, butless so for TLN. To discriminate the light quantity and periodcomponents in DtB, two novel temporal indicators were determined,LtB (photosynthetic time to bolting) and PChron (DtB h^–1of photoperiod), respectively. The use of PChron results ina coincidence of the variation profiles across stPhP and exPhP,interpreted as a buffering of the trophic response. Unlike naturalaccessions and later flowering mutants, the variation profilesacross stPhP and eav mutants are significantly divergent, pointingto differences in environmental and genetic variation in floweringtime. Yet, phenocopy effects and dynamic convergence betweenwild-type and mutant profiles are detected by using exPhP andthe LtB indicator. Additional analyses of the cauline leaf number(CLN) show that the apical and basal boundaries of the primaryinflorescence vary co-ordinately. The finding that the correlativitybetween CLN and TLN changes across photoperiods suggests thatdifferent states of intra-connectedness are involved in ontogeneticspecification of flowering time and embodied in the primaryinflorescence. Key words: Arabidopsis, bolting, correlativity, developmental dynamics, flowering time, early flowering mutant, phase change, phenocopy, phenotypic plasticity, photoperiodic response