Interacción déficit hídrico-ambiente lumínico en la respuesta fotosintética de plantas de soja (Glycine max (L.) Merril)

Soybean is the main agricultural crop in Uruguay. Its yield varies depending on water conditions during growth, the availability of soil nutrients, as well as the light environment for growth. The objective of the study was to analyze the photosynthetic activity response in soybean (Glycine max) leaves to changes in light environments with different spectral compositions (white light, white light enriched in red, blue light, and red light) and water conditions (control and Deficit). Two genotypes (Don Mario 6.8i and Génesis 5601) were used, and four replicates were performed per treatment. The treatments were defined by the interaction of the genotype factor (Don Mario 6.8i and G5601), the water condition factor (control and Deficit), the light environment factor (White1, White2, Blue, and Red), and a level of actinic light factor (850 μmol photons m⁻² s⁻¹). Energy partitioning in PSII was studied based on three main parameters (Φ_PSII, Φ_NPQ, and Φ_NO) and two sub-parameters (Φ_NPQ._fast and Φ_NPQ.slow). Additionally, variance analyses were conducted to determine whether there was a significant effect of the factors on the studied parameters, and a contrast analysis was performed to establish differences between the treatment means. It was evident that the light environment during the development of a soybean plant determines PSII efficiency, as well as that the spectral quality of the development light environment determines the energy partitioning strategy in a functional soybean leaf. It was also found that the combination of water deficit and spectral deficiency reduces the efficiency of the photochemical phase of the photosynthetic process.