Abstract
Low temperature at stand establishment and high temperature at reproductive stage are involved in reduction of grain yield of spring maize. A field study was therefore conducted to evaluate different physiological strategies for improving performance of spring maize under temperature extremes. Seed priming and foliar spray with 3% moringa leaf extract (MLE) and 100 mg L-1 kinetin solution alone or in all possible combinations with each other at three growth stages (knee height, tasseling and grain filling stage) and hydropriming was compared with control. Seed priming plus foliar spray of MLE and kinetin significantly improved stand establishment especially under early sown crop as indicated by reduced mean emergence time (MET), improved emergence index (EI) and final emergence percentage (FEP). Similarly increased chlorophyll contents, crop growth rate, leaf area index, photosynthetic rate, transpiration rate, relative water content and decreased membrane permeability were recorded in both early and optimum sowing conditions in MLE priming plus foliar spray treatment. All these improvements were harvested in the form of increased yield and harvest index compared with control treatment. Overall crop sown at optimum time performed best but exogenous application of MLE through seed priming and foliar spray maximally improved the performance of early sown maize crop which is attributed more likely due to improved stand establishment, chlorophyll and phenolic contents, increased leaf area duration and grain filling period. It can be concluded that seed priming with MLE along with its foliar spray could increase production of maize under temperature extremes.
Highlights
Out of 1.1 billion tons of coarse grains produced in the world during 2010 for food, feed and industrial purposes, maize accounts for 74% of aggregate output [1]
Priming and foliar techniques include hydropriming, seed priming with kinetin, seed priming with moringa leaf extract (MLE), water spray, foliar spray of kinetin, seed priming plus foliar spray of MLE and seed priming plus foliar spray of kinetin
Suboptimal temperature decreased the emergence count in early sown maize crop by causing chilling injury to the growing seeds. Besides this realization that chilling stress considerably increased the mean emergence time and decreased final emergence percentage in early sown maize crop, seed priming with growth promoting substances like MLE and kinetin significantly reduced mean emergence time (MET) and increased emergence index (EI) and final emergence
Summary
Out of 1.1 billion tons of coarse grains produced in the world during 2010 for food, feed and industrial purposes, maize accounts for 74% of aggregate output [1]. Spring Maize Enhancement by Physiological Strategies high day temperatures of 38°C at reproductive stage directly affect pollination and seed setting resulting in reduced grain yield [2]. One possible option to avoid heat stress is early planting of spring maize. Planted spring maize has experienced a decrease in daily soil temperature below 10°C that causes imbibitional injury to germinating seed [4]. Low temperature stress at early developmental stages resulted in poor photosynthetic performance of maize [5], which further leads to retarded plant growth and development [6]. Higher activities of reactive oxygen species has been observed that cause oxidative damage to membranes and impairs the normal functions of cells by reacting with proteins, lipids and DNA [7]
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