Perturbations of malate accumulation and the endogenous rhythms of gas exchange in the Crassulacean acid metabolism plant Kalanchoë daigremontiana: testing the tonoplast-as-oscillator model.

摘要: In continuous light, leaves of the Crassulacean acid metabolism (CAM) plant Kalanchoe daigremontiana Hamet et Perrier exhibit a circadian rhythm CO2 uptake, stomatal conductance and leaf-internal pressure. According to current quantitative model CAM, pacemaking mechanism involves periodic turgor-related tension relaxation tonoplast, which determines direction net flux malate between vacuole cytoplasm. Cytoplasmic malate, in turn, through its inhibitory effect on phosphoenolpyruvate carboxylase, controls rate uptake. this mechanism, when accumulation is disrupted by removing from ambient air, induction phase delay with respect an unperturbed control expected. First, using mathematical model, such delays were observed numerical simulations three scenarios removal: (i) starting at trough lasting for about half cycle (ca. 12 h vivo); (ii) identical phase, but 1.5 cycles 36 h); (iii) while increases, again. Applying same protocols K. vivo did not induce predicted shifts, i.e. after end removal perturbed adopted nearly as that plant. Second, exposed nitrogen atmosphere nights prior onset light prevent accumulation, small, 4-h advance was instead delay, again contrary model-based expectations. Hence, vacuolar malic ruled out central process. This observation line our earlier suggestion [T.P. Wyka, U. Luttge (2003) J Exp Bot 54:1471–1479] extended uptake switches gradually CAM-like C3-like oscillations two systems being tightly coordinated. It appears gas exchange CAM emerges one or several devices are capable generating temporal information robust manner, they protected even severe metabolic perturbations.