CONICET | Buscador de Institutos y Recursos Humanos

Abstract: Heat stress (HS) combined with water stress (WS) negativelyimpact soybean [Glycine max (L.) Merr.] production. The aims of thisresearch were to quantify the combined effect of HS and WS during grainfilling (GF) on grain yield, and to identify physiological-biochemicaltraits strongly associated to crop performance and yield determinationprocesses under these stressful field environments. Two soybean cultivarswere exposed during GF to ambient temperature or to HS (> 32 °C for 6 hper d) during 21 d; and to field capacity or to WS (20% of available soilwater content) during 35 d. Yield was significantly reduced under HScombined with WS but also in irrigated plots, due to diminutions in grainnumber and weight (GN and GW). Final GW of irrigated HS was similar tothat of control, highlighting compensation mechanisms. Chlorophyllfluorescence analysis indicated that detrimental effects of HS and WS onphotosynthesis were via structural capacity aspects but also throughdamage to photosystem II. The HS × WS decreased the availability ofassimilate to grains, but also impaired the sink-grain metabolization ofthe remobilized products from leaves. A multivariate analysis highlightedstrong correlations between quantum efficiency of photosystem IIphotochemistry, chlorophyll content (SPAD value), and the antioxidantstate of leaves, which were all positively correlated with yield. Canopytemperature throughout grain filling (CTGF) was negatively associatedwith GN and GW, the latter also positively associated with SPAD.Explaining these physiological traits 81, 50, and 82% of the totalvariability of yield, GN and GW, respectively. To our knowledge this isthe first report that integrating different scales of study, demonstratesthe potential of physiological-biochemical parameters to explain yieldvariations in field-grown soybean under HS and WS conditions.

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