Title: Effects of high night temperature and abscisic acid (ABA) on rice (Oryza sativa L.) physiology Authors
|Mohammed, Abdul -|
|Tarpley, Lee -|
Submitted to: Rice Technical Working Group Meeting Proceedings
Publication Type: Proceedings
Publication Acceptance Date: February 5, 2014
Publication Date: N/A
Technical Abstract: High night temperature (HNT) is known to decrease rice yields. The impact of abscisic acid (ABA) on plants has been the subject of many studies. However, little or no work has been carried out on rice response to ABA under HNT-stress conditions. This study determined the effects of ABA on rice leaf photosynthetic rate, photochemistry, respiration and physiology under HNT-stress conditions. Plants were grown under ambient night temperature (ANT) (25 oC) and HNT (30 oC) in the greenhouse. They were subjected to a HNT through use of continuously controlled infrared heaters, starting from boot stage of the rice plants until harvest. Night temperatures were imposed from 2000h until 0600h. Plants were treated with ABA at boot stage of the rice plant. Net photosynthesis of the penultimate leaf was measured between 1000 h and 1200 h using a LI-6400 portable photosynthetic system (LI-COR Inc., Lincoln, Nebraska, USA), 5 days after treatment (DAT). Respiration rates were measured on the penultimate leaf between 2400 h and 0200 h using a LI-6400, 5 DAT. Pollen viability was determined using a staining technique (IKI) and pollen germination was determined in vitro. Spikelet fertility was defined as the ratio of filled grains to total number of grains in the panicle. Grain length, width, surface area, volume and chalkiness of brown (dehulled) rice were determined using a Winseedle, which uses analysis of scanned color images of the grain to calculate these parameters. Grain nitrogen concentration was measured using a FP-528 Nitrogen/Protein analyzer. High night temperature decreased leaf photosynthetic rate (5%), stomatal conductance (21%), spikelet fertility (5%) and yield (6%) and increased respiration rate (74%) and grain chalkiness (221%). The application of ABA increased leaf photosynthetic rate (6%) as a result of increased stomatal conductance (18%), quantum yield (8%) and electron transport rate (8%), under HNT. In addition, application of ABA decreased non-photochemical quenching (41%) and respiration rate (33%), under HNT. The ABA-treated plants grown under HNT showed increased spikelet fertility (10%) and yield (13%) as a result of increased leaf photosynthetic rate and decreased respiration. Abscisic acid has the potential to be used as a plant growth regulator to partially negate high night temperature stress.