Photothermal quotient captures adequately the combined effects of heat and shade stresses on canola productivity

RIVELLI GM; GOMEZ N; ABELEDO LG; MIRALLES DJ; RONDANINI DP

Santa Fe

Congreso; XXXIII Argentinian Meeting of Plant Physiology; 2021

Sociedad Argentina de Fisiología Vegetal

Shading and heat stress during critical reproductive period affect negatively yield in canola (Brassica napus L.), however, the impact of combined effect of both stresses has not yet studied. Although photothermal quotient (radiation:temperature ratio) is commonly associated with seed yield, its utility under combined stress conditions is unknown. This work was aimed to (i) evaluate the effects of shading and heat stress, alone and combined, on seed yield and quality, (ii) quantify the resulting effect (additive, synergistic, antagonistic) of combined stresses, and (iii) examine the utility of the photothermal quotient to predict seed yield in stressed crops. Two experiments were carried out under field conditions in Buenos Aires (34°35′S, 58°29′W) applying to a canola hybrid a high daytime temperature stress (HT, 25-30°C average from 10:00 to 15:00), a shading stress (SH, -80% irradiance), and combined stresses (SH+HT), with an unstressed Control (C, 20°C and 100% irradiance). Exp 1 was longer (37 d) and less hot than Exp2, which was short (10 d) and heated more intensely. Treatments overlapped the critical periods of 100-500 ºCd and 200-400 ºCd after flowering defined in the literature. Long and short duration SH and HT strongly affected seed yield (reduction from -40 to -90%). Combined SH+HT exhibited additive effects on seed yield and oil concentration for long duration stresses. Photothermal quotient (accumulated between 100-500 °Cd) captured adequately (p