Thermoperiodic growth control by gibberellin does not involve changes in photosynthetic or respiratory capacities in pea

Abstract

Active gibberellin (GA1) is an important mediator of thermoperiodic growth in pea. Plants grown under lower day than night temperature (negative DIF) elongate less and have reduced levels of GA1 compared with plants grown at higher day than night temperature (positive DIF). By comparing the wild type (WT) and the elongated DELLA mutant la crys, this study has examined the effect of impaired GA signalling on thermoperiodic growth, photosynthesis, and respiration in pea. In the WT a negative DIF treatment reduced stem mass ratio and increased both root mass ratio and leaf mass ratio (dry weight of specific tissue related to total plant dry weight). Leaf, root and stem mass ratios of la crys were not affected by DIF. Under negative DIF, specific leaf area (projected leaf area per unit leaf dry mass), biomass, and chlorophyll content of WT and la crys plants were reduced. Young, expanding leaves of plants grown under negative DIF had reduced leaf area-based photosynthetic capacity. However, the highest photosynthetic electron transport rate was found in fully expanded leaves of WT plants grown under negative DIF. Negative DIF increased night respiration and was similar for both genotypes. It is concluded that GA signalling is not a major determinant of leaf area-based photosynthesis or respiration and that reduced dry weight of plants grown under negative DIF is caused by a GA-mediated reduction of photosynthetic stem and leaf tissue, reduced photosynthesis of young, expanding leaves, and reduced growth caused by low temperature in the photoperiod.

Effect of difference between day and night temperature on tomato (Lycopersicon esculentum Mill.) root activity and low molecular weight organic acid secretion

“…Merr.) (Stavang et al 2010). Similar results have been reported for cucumber (Cucumis sativus L.) (Patil and Moe 2009;Xiong et al 2011), tomato (Xu 2004), and rice (Oryza sativa L.) (Bai et al 2007).…”

“…In this study, the low day temperatures (19 and 22°C) and high night temperatures (28 and 31°C) of negative DIF treatments limited photosynthesis, which inhibited the growth of tomato aerial parts and roots, and resulted in a low root/shoot ratio (Table 1). High night temperature (28 and 31°C) has been shown to increase plant respiration, and decrease net assimilation (Stavang et al 2010). Under negative DIFs, gibberellin regulation reduced plant dry matter and photosynthetic rates of stem and leaf tissues of pea (Glycine max (Linn.)…”

Reply: Interaction between Brassinosteroids and Gibberellins: Synthesis or Signaling? In Arabidopsis, Both!

“…GA biosynthesis is highly regulated by exogenous stimuli (Stavang et al, 2005(Stavang et al, , 2010Weller et al, 2009), which must be taken into account when GA-related phenotypes are studied. For example, in BR mutants, a 4˚C treatment fully recovered germination defects (Unterholzner et al, 2015), indicating that cold may act independently of BRs to induce GA biosynthesis during germination.…”

Assessing in vitro germination and seedling growth of tomato (<em>Solanum lycopersicum</em> L.) cv KC-1 in response to polyethylene glycol-induced water stress

“…The root: shoot ratio represents the partitioning of biomass between root and aerial parts and it is an important index for evaluating plant health. Well-developed roots of the seedling help in nutrient and water absorption (Stavang et al, 2010). A strong positive correlation with significant effect was noted between shoot length and fresh weight of seedling for the combined data according to the Pearson correlation.…”