Assessing the Effects of High Night Temperature on Rice Photosynthetic Parameters: Involvement of Cellular Membrane Damage and Ethylene Response

Abstract

Plant ecophysiological response to environmental stresses involves sub-organismal mechanisms. For example, elevated ethylene levels can promote the degradation of chlorophyll (CD) and damage to the cellular membranes (MD), leading to decreased photosynthetic rate (PN) and photosynthate transfer, as well as increased respiration (RS) under heat stress, causing loss of yield. To determine the extent of contribution of ethylene-triggered responses in rice plants under high night temperature (HNT; 30 °C) stress, the capability of applied ethylene perception inhibitor, 1-methylcyclopropene (1-MCP), to prevent rice yield loss by minimizing HNT-induced, ethylene-promoted CD and MD, was examined. Rice was subjected to either 30 or 25 °C (ambient night temperature (ANT)); under each night temperature regime, sets of plants received 1-MCP application or not. High night temperature increased CD (7%), MD (46%), and RS (28%) and decreased PN (6%), pollen germination (42%) and spikelet fertility (SF; 31%), and yield (14%). In response to 1-MCP application, plants grown under HNT showed decreased CD (from 8 to 10.6 μg cm−1), MD (from 42% to 35%), and RS (from 1.3 to 0.9 μmol m−2 s−1) and increased SF (49.5 to 70%), pollen germination (15 to 18.9%), and yield (15 to 17.7 g plant−1). The 1-MCP application increased SF and brought rice yields under HNT up to levels observed under ANT as a result of increased pollen germination and decreased RS and MD, indicating that ethylene-triggered responses are a major component of rice response to HNT.