Abstract:

In order to develop water saving irrigation stratagem and increase cotton yield in Xinjiang, we did the irrigation experiment in the field, controlled the lower limit of soil relative moisture content in layer of 0–60 cm at 45%, 60%, and 75% (the control) respectively of field water-holding capacity, which was the upper irrigation limit, and studied the effects of rewatering after drought on photosynthesis and yield during flowering-boll stage of cotton under-mulch-drip irrigation. The result showed that drought reduced the parameters of gas exchange. Photochemical quenching coefficient (qP) and P_SⅡ photochemical quantum yield (Ф_PSⅡ) were reduced but non-photochemical quenching coefficient (NPQ) was increased significantly under moderate drought. Net photosynthetic rate (P_n) and stomatal conductance (G_s) of three water treatments could be rapidly recovered within three days after rewatering, and the recovery of mild drought treatment was the most rapid. The recovery of Ф_PSⅡ and qP in three water treatments was similar to that of P_n which achieved the maximum in 2–3 days after rewatering. The NPQ of three water treatments decreased significantly in 1–2 days after rewatering. From early flowering stage to early full boll stage, accumulation of single plant photosynthate was not much different from that of mild drought treatment after rewatering and the control, but the accumulation of single plant photosynthate was decreased significantly from later full boll stage to boll opening stage that let the seed cotton yield in mild drought treatment after rewatering be lower than that in control. Accumulation of single plant photosyn-thate and seed cotton yield in moderate drought treatment after rewatering was always lower than that in mild drought treatment and control.

Key words: Cotton (Gossypium hirsutum L.), Drought, Rewatering, Photosynthesis, Xinjiang, Under-Mulch-Drip irrigation