Effect of the Alternating Stresses of Drought and Waterlogging on the Growth, Chlorophyll Content, and Yield of Rice (<i>Oryza sativa</i> L.)

Abstract

The height, number of tillers, chlorophyll (Chl) a and b content, and yield of rice (Oryza sativa L.) in response to alternating stresses of drought and waterlogging (ASDW) at the tillering and jointing stages were evaluated in a greenhouse. This was done to simulate field conditions and explore appropriate water management strategies, including the use of rainwater. The experiment tested four different ASDW treatments and regular irrigation (CK) in 2012 and 2013. The ASDW treatments were light drought + light waterlogging + light drought (T-LD) and severe drought + light waterlogging + severe drought (T-HD) at the tillering stage, and light drought + light waterlogging + light drought (S-LD) and severe drought + light waterlogging + severe drought (S-HD) at the jointing stage. CK was the control. Plant heights at harvest stage with the T-HD and T-LD treatments were 7.35 and 8.65&nbsp;cm higher than plant heights with CK in 2012, while plant heights with the S-HD and S-LD treatments were lower than plant heights with CK in 2012 and 2013. Compared with CK, the number of tillers with the T-LD and T-HD treatments was reduced by approximately 1 to 2, and the number of ineffective tillers in the S-LD and S-HD treatments was reduced by approximately 2 to 3 and 2 to 4, respectively. After ASDW with the T-LD and T-HD treatments the Chl a and b content increased in 2012, but with the S-LD and S-HD treatments the Chl a and b content decreased by 8.11% and 10.81%, respectively, in 2013. Decreases in the 1,000-grain weight and filled grains per spike were the main causes of yield reduction. Yield per pot with the T-LD and T-HD treatments decreased by 29.25% and 25.37%, respectively, in 2013 (P&lt;0.05). Yield per pot with the S-LD and S-HD treatments decreased by 19.01% and 39.80%, respectively, in 2013 (P&lt;0.05). The harvest index values for the T-LD and T-HD treatments were higher than those for CK. The irrigation water use efficiency (IWUE) value for the T-HD treatments improved by 46.77% (P&lt;0.05) in 2012, and the IWUE value for the S-HD treatments decreased by 29.78% in 2013.