Architectural Engineering of Rice Panicle for Increased Productivity: A Powerful Biological Tool for Combating Agricultural Water Crisis

Abstract

Grain sterility in rice increases with plant water deficit, particularly during panicle development. We compared certain aspects of water relations of rice panicle with that of flag leaf. The emerging young rice panicles transpired more water than the flag leaves, despite the latter being heavily lashed with stomata. On an individual organ basis, the rate of water loss by panicle was about 4.5 times greater (45 × 10⁻⁴ ml min⁻¹ panicle⁻¹) than the rate exhibited by flag leaf (10 × 10⁻⁴ ml min⁻¹ leaf⁻¹), whereas on an equal or unit area basis, the magnitude of difference in water loss was 22 times higher (33.5 × 10⁻⁶ ml min⁻¹ cm⁻²) than the rate of water loss by flag leaves (1.3 × 10⁻⁶ ml min⁻¹ cm⁻²). Panicles coated with gypsum, covered by polythene bags, compacted with threads or devoid of awns had a significant impact on the rate of water loss. For cv. NDRH-2, water loss was less when panicle was coated with gypsum than when it was covered with polythene bags or compacted with threads in that order, i.e., gypsum coating > polythene covering > compacting. Further, awns inhibited water loss in cv. Tipakhiya. Open panicles of cv. Sathi transpired more water than those inherently hidden inside the leaf sheaths. Barriers to water loss increased the water content and viability of the panicles during soil-moisture stress. Increased panicle water content decreased the spikelet desiccation injury and spikelet sterility during plant water stress. We concluded that it was the excessive water loss by panicles, not leaves, and the diurnal fluctuations, which appeared to be the first and foremost signal-transduction stimulus, that caused the commonly observed grain sterility and its irregular and random distribution within the panicle.

KEYWORDS:

• Architectural engineering
• biological tool
• grain sterility
• panicle
• potometer
• relative water content
• rice (Oryza sativa L.)
• transgenic approaches
• transpiration
• water loss

The authors sincerely thank Dr. S.P. Giri and Mr. R.A. Yadav of N.D. University of Agriculture & Technology, Faizabad (U.P.), India, for supplying seeds for these studies, as well as Dr. M.K. Sharma, Associate Professor for statistical analysis of the data, and Dr. S. Rajan, Principal Scientist, Central Institute for Sub-Tropical Horticulture, Lucknow, for preparing the figures.