Asian Research Thesis Index

Abstract

Water-limited conditions in early growth stages negatively affect germination and seedling growth, often leading to suboptimal plant population and poor stand establishment. Germination and seedling growth of ten local wheat (Triticum aestivum L.) genotypes in response to induced water stress conditions and supplemental foliar fertilisation with macronutrients (NPK) were investigated. In two laboratory experiments, the observed germination parameters and calculated stress indices were used as screening criteria for drought tolerance. In one glasshouse experiment, the dose and combinations of N, P, and K for foliar spray were optimised. Germination parameters viz. germination percentage, germination index, promptness index, and germination stress tolerance index declined in response to the increasing polyethylene glycol induced stress levels. Water stress conditions imposed by withholding irrigation at seedling stage reduced plant height stress tolerance index and dry matter stress tolerance index but increased root length stress tolerance index and root to shoot ratio. Based on the results of germination attributes and stress indices, Bhakkar-02 was the most drought tolerant genotype and Shafaq-06 was the most drought sensitive genotype among all tested genotypes. Supplemental foliar fertilisation of macronutrients (N, P, and K), alone or in different combinations improved the water relations, gas exchange characteristics and nutrient contents in both contrasting genotypes, Bhakkar-02 and Shafaq-06. Foliar spray NPK in combination was the most effective treatment in improving plant growth under both well- watered and water-deficit conditions. Subsequently, the best combination of foliar NPK was tested in wire house and field conditions to evaluate the most appropriate growth stage for supplemental fertilisation. In wire house experiment foliar application of NPK spray improved the water relations, gas exchange characteristics (i.e. through accumulation of soluble sugars), total free amino acid, and proline. The antioxidant activity was also improved with foliar NPK spray at anthesis stage. In field experiments foliar application of NPK in combination improved the number of grains per spikelet and 1000-grain weight, which ultimately increased the grain yield at anthesis stage in normally irrigated plants as well as under water stress conditions at anthesis stage in both wheat genotypes. The water shortage at anthesis stage decreased the yield and its components more severely as compared to tillering stage. The drought tolerant Bhakkar- 02 performed well under water stress. So, foliar application of NPK at anthesis stage under water stress conditions gave better results as compared to tillering stage

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