Involvement of 1-Methylcyclopropene in Plant Growth, Ethylene Production, and Synthase Activity of Inferior Spikelets in Hybrid Rice Differing in Panicle Architectures

Abstract

Chlorophyll content (SPAD values) of leaves, 1-aminocyclopropane-1-carboxylic acid synthase (ACS) activities and ethylene production of inferior spikelets, aboveground biomass, grain yield, and yield components were studied to compare the effects of 1-methylcyclopropene (1-MCP) on plant growth, and inferior spikelet development in hybrid rice (Oryza sativa L.) differing in panicle architectures. There were four hybrid rice cultivars in this trial, including two lax-panicled cultivars, Liangyoupeijiu (LYPJ) and Guodao 6 (GD6), and two compact-panicled cultivars, Yongyou 9 (YY9) and Yongyou 12 (YY12). Results showed that chlorophyll content of leaves in 1-MCP treatment was higher than control (CK) after application of 1-MCP. ACS activities and ethylene production in 1-MCP treatment for LYPJ, GD6, and YY9 were significantly decreased compared to their corresponding CK. Aboveground biomass and grain yield of cultivars were increased with the increase of chlorophyll content of leaves, but decreased with the increase of ACS activities and ethylene production of inferior spikelets. On average, grain yield in 1-MCP treatment for LYPJ was increased by 7.3 % compared to CK, GD6 was increased by 2.6 %, YY9 was increased by 3.2 %, and YY12 was increased by 0.8 %, respectively. Application of 1-MCP showed marked effects on increasing spikelet fertility and harvest index of cultivars, but exhibited little effects on improving sink capacity and 1,000-grain weight. Our results indicate that 1-MCP could play a positive role in regulating the growth and development of hybrid rice with lax panicles or with compact panicles.