Growth analysis serve a significant perspective on the yield and physiological aspects of crop plants. In the early stages of plant growth, the growth indicators, including the leaf area index (LAI), the crop growth rate (CGR) of decreases, and then due to suitable vegetation conditions, the absorption of light radiation will be better, and the accumulation of plant dry matter also increases, and after that due to plant aging and yellowing, the number of leaves and LAI are reduced. The amount of light radiation absorbed by the plant varies during the crop growth period, which depends on the Leaf Area Index (LAI) and the arrangement of the leaves on the plant.
Materials and Methods
The experiment was conducted in the research farm of Khuzestan University of Agricultural Sciences and Natural Resources in 2021-2022. In this research, the effect of three factors of irrigation interruption, rapeseed genotypes and plant density was investigated in the form of factorial split with the base design of randomized complete blocks in three replications. The factor (no interruption of irrigation (control), interruption of irrigation at the beginning of flowering until the formation of 50% of the pod and interruption irrigation at the stage of pod formation until harvest the main factor, rapeseed cultivars Hayola 4815 and Aram and plant density per meter square (80, 110 and 140 plants per square meter) were considered as secondary factors.
Result and Discussion
Irrigation interruption caused a decrease in growth indicators, including the amount of plant dry matter accumulation, leaf surface index, and leaf surface durability. The changes in harvest index and durability of leaf surface and accumulation of dry matter at the beginning of the development of leaves had a slow trend until a little before the appearance of inflorescences, but after that the slope of the mentioned parameters increased. During the experiment, changes in growth parameters including LAI, LAD, RGR, CGR and TDW were evaluated. At the beginning of the plant growth season, the growth rate of the product was low due to the lack of complete vegetation cover and proper light consumption efficiency. In all treatments, with the passage of time, the growth rate of the crop was gradually increasing and it reached the maximum value in the reproductive stages and then went through a decreasing process. The effects of stopping irrigation on dry weight were evident and the accumulation of dry matter was observed during the increasing time, which can be due to the increase in dry weight of stems, leaves and reproductive organs over time. Also the relative growth rate also showed an increasing trend with the increase of the leaf area index at first and then a decreasing trend.
The highest amount of grain yield, active photosynthetic radiation and the lowest light consumption were assigned to Hayola 4815 genotype. Aram genotype had a high leaf area index and increasing the leaf area index too much in the plant causes more shading of plants on top of each other and young leaves turn into older leaves.