Modeling the Effect of Plant Density on Leaf Production and Senescence of Wheat in Terminal Stage Water Holding Conditions

Background and Objectives Wheat (Triticum aestivum L.) is one of the world's major cereal crops. Approximately, one sixth of the total arable land is cultivated with wheat. Plant density is an important management factor on crop yield. A major component in a crop growth model is leaf area development which has a major influence on photosynthesis and transpiration. Leaves senesce because of the natural biological process of ageing, but the effect of water deficit can markedly reduce leaf longevity. The aim of this research was to model the effect of plant density on the production and aging leaves of two wheat cultivars (Gascojen and Pishtaz) under irrigation cut off conditions at the end of growth period.
Materials and Methods In order to model of leaf production and senescence in wheat, the experiment was conducted as a factorial based on randomized complete block design with four replications. The experiment was carried out at research farm of Saleh abad, Torbatjam, Iran in 2011. Treatments of this experiment were plant densities (50, 100, 200, 300, 400 and 500 plant in m2) and cultivars (Gaskojen and Pishtaz). In this experiment, irrigation was removed in stem elongation and seed development stages.
Results Phyllochron in wheat approximately was 102 GDD and showed ending after receiving 900 GDD. Plant density had no effect on leaf appearance and phyllochron. Leaf senescence in the main stem started when the main stem had about 5 leaves and proceeded at a rate of 0.7 per unit increase in GDD. Leaf production per plant versus main stem leaf number occurred in two phases; phase 1. Production increased when plant leaf number occurred with a slower and density-independent rate: phase 2. Production increased with a higher and density-dependent rate of leaf. A close relationship was found between the fraction of senesced leaves per plant and the same fraction on the main stem. Leaf lifetime average decreased with increasing density. Gaskojen was paramount to pishtaz variety in number and lifetime of leaf.
Discussion The results showed that leaf production and senescence of wheat in different plant densities on terminal stage water holding conditions could be quantified using different equations