Interactions of shading conditions and irrigation regimes on photosynthetic traits and seed yield of soybean (Glycine max L.)

Field experiments were conducted in 2013 and 2014 with eight treatments consisting of combination of four shading periods (shading during vegetative phase (V), reproductive phase (R), whole growing season and a control treatment) and two irrigation regimes (irrigation after depleting 40 and 80% of available water). Under limited irrigation conditions, the highest PSII quantum yield, the capacity of electrons move beyond QA and electron move from intersystem to PSI acceptor side reduced, with greater decline degree in sunlight treatment. The minimum seed yield was recorded by plants treated with limited irrigation and whole growing season shade. Changes in the state of the photosynthetic electron transport chain and photorespiration rates in response to different shading treatments were primarily related to leaf water loss. In general, the results revealed that shading caused some shade avoidance responses in soybean, which finally reduced seed production.