Effect of Plant Density on Allometric Relationships between Leaf Area and Vegetative Traits of Wheat

IntroductionCrop models are the most important components of ecological models. These models could provide the possibility of crop systems prediction in addition to increase the understanding of their performance. Allometric relationships of plants show changes of growth of one part in comparison to other parts of the plant. Determine the appropriate plant density in crops, especially wheat has the high importance which affects some characteristics such as yield and yield component. This affects varies in different stages of plant growth.
Materials and MethodsThis research has been done in research station of Gorgan University of Agricultural Sciences and Natural Resources (37,45N, 54,30E and 120m above sea level) in the growing season of 2012-13. The experiment was conducted in a factorial experiment with randomized complete block design with four replications as base. Treatments consisted of two wheat cultivars (Koohdasht and Morvarid) and 7 plant densities (50, 100, 200, 350, 500, 650, 800 seed.m2). Each replication consisted of 14 plots and each plot had 10 rows with length of 5 m, width of 2 m and a row spacing of 20 cm. Plot distances from each other was 40 cm and block distances was 1 m to each other. Measurements were done from tillering to the end of the growing every 7 to 10 days (depending on weather conditions). Cumulative thermal units were calculated using GDD_Calc program. Power model and non-liner segmented regression model were used to describe allometric relationships.
Results and DiscussionFor fitting equations related to leaf area versus days after planting, coefficient of determination was 0.73 and root mean square error ranged between 0.37 and 0.77 which revealed that the logistic model could well describe increasing leaf area during the time. There is a significant effect for a, b and c coefficients in different plant density of wheat and increasing density could lead to -the increasing coefficient and decreasing the a and b coefficients. In addition, regarding the relationship between leaf area and number of leaves in different plant density, coefficient of determination values greater than 0.87 and ranges of root mean square error between 9.65 and 24.39, belong to the plant densities of 800 and 50, respectively, which showed a good correlation between leaf area per plant and the numbers of leaves. In this regard, b coefficient has a significant difference in various wheat density.
The relationship between leaf area and green leaf dry weight coefficient of determination greater than 0.78 and the root mean square error between 31.44 and 17.68, respectively belong to plant density of 350 and 100 with no significant difference in b coefficient. In connection with the relationship between leaf area and plant height, coefficient of determination greater than 0.85 and the root mean square error between 9.29 and 21.13 cm.m-2.plant-1 respectively belong to plant density of 800 and 200. We found a significant difference in b coefficient and decrease about 0.0003 unit with increasing plant density.
ConclusionsThe results of relation between leaf area of each plant with the number of leaves in main stem, dry weight of green leaf and plant height showed good allometirc correlation until booting stage (0.87, 0.78 and 0.85, respectively). In addition, significant effects were investigated for correlation between leaf area of each plant and the number of leaves and plant height, however, correlation between leaf area of each plant and dry weight of green leaf area of plant was not significant.