Abstract
We assessed mechanistic temperature influence on flowering by incorporating temperature-responsive flowering mechanisms across developmental age into an existing model. Temperature influences the leaf production rate as well as expression of FLOWERING LOCUS T (FT), a photoperiodic flowering regulator that is expressed in leaves. The Arabidopsis Framework Model incorporated temperature influence on leaf growth but ignored the consequences of leaf growth on and direct temperature influence of FT expression. We measured FT production in differently aged leaves and modified the model, adding mechanistic temperature influence on FT transcription, and causing whole-plant FT to accumulate with leaf growth. Our simulations suggest that in long days, the developmental stage (leaf number) at which the reproductive transition occurs is influenced by day length and temperature through FT, while temperature influences the rate of leaf production and the time (in days) the transition occurs. Further, we demonstrate that FT is mainly produced in the first 10 leaves in the Columbia (Col-0) accession, and that FT accumulation alone cannot explain flowering in conditions in which flowering is delayed. Our simulations supported our hypotheses that: (i) temperature regulation of FT, accumulated with leaf growth, is a component of thermal time, and (ii) incorporating mechanistic temperature regulation of FT can improve model predictions when temperatures change over time.
Highlights
Ambient temperature during the growing season correlates with the timing of plants’ transition from vegetative to reproductive growth
The FLOWERING LOCUS T (FT) induction by fluctuating temperatures was incorporated through CO transcript, which was induced in response to a change to cool temperatures like that observed (Figure 3a-b)
There was a strong relationship between the amount of simulated and observed CO transcript across treatments, as calculated as the area under the curve (AUC, Figure 3c); FM-v1.5 does not incorporate the CO suppression observed when plants are grown at constant 12 ̊C from seed
Summary
Ambient temperature during the growing season correlates with the timing of plants’ transition from vegetative to reproductive growth. Germination, organ emergence, leaf expansion, photosynthesis, and respiration display similar relationships (Parent et al, 2010). These findings have led to the concept of “thermal time” (Lehenbauer, 1914), a metric that asserts that temperature-driven metabolic rates govern development (Zavalloni et al, 2006), and to models that use the empirical relationship between temperature and development to predict plant response (e.g., Chuine, 2000; Jones et al, 2003). Thermal units accumulate more quickly, and reach a predetermined threshold sooner to predict flowering, during warm growing seasons than cool ones.
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