Comparison of environmental and mutational variation in flowering time in Arabidopsis

Developmental dynamics can be influenced by external and endogenous factors in a more or less analogous manner. To compare the phenotypic effects of (i) environmental [i.e. standard (stPhP) and extended (exPhP) photoperiods] changes in Arabidopsis wild types and (ii) endogenous genetic variation in eav1-eav61 early flowering mutants, two temporal indicators were analysed, the time to bolting (DtB) and the number of leaves (TLN). It was found that DtB and TLN are differentially affected in different environmental and genetic contexts, and some factors of dynamic convergence were identified. The quantitative response to photoperiod is markedly contingent on the phototrophic input for DtB, but less so for TLN. To discriminate the light quantity and period components in DtB, two novel temporal indicators were determined, LtB (photosynthetic time to bolting) and PChron (DtB h(-1) of photoperiod), respectively. The use of PChron results in a coincidence of the variation profiles across stPhP and exPhP, interpreted as a buffering of the trophic response. Unlike natural accessions and later flowering mutants, the variation profiles across stPhP and eav mutants are significantly divergent, pointing to differences in environmental and genetic variation in flowering time. Yet, phenocopy effects and dynamic convergence between wild-type and mutant profiles are detected by using exPhP and the LtB indicator. Additional analyses of the cauline leaf number (CLN) show that the apical and basal boundaries of the primary inflorescence vary co-ordinately. The finding that the correlativity between CLN and TLN changes across photoperiods suggests that different states of intra-connectedness are involved in ontogenetic specification of flowering time and embodied in the primary inflorescence.