Abstract:

With the development of computer graphics and crop simulation, virtual crop study, intuitionally expressing crop growth on computer, attracted many scientists to focus on this field. Some scientists have made great progress on the visualization of wheat, maize, soybean, rice and cotton, etc. Leaf shape is a very important characteristic in virtual crop growth modeling, and some empirical curves have been used to describe leaf morphology based on field experiments in the previous study. The fitting curves can help to understand organ morphogenesis, but the fitting parameters obtained from the given leaves and time cannot suit to changed growth process of leaves. So developing a mechanism model to simulate the leaf morphology is critical for virtual crop growth.
Organ morphogenesis of plant is decided to its forces. After force analysis on a rice leaf, the gravity fraction in leaf normal direction keeps equilibrium with elasticity, and then a dynamic leaf curvature equation was deduced with some assumption. The equation included the synthetic effect of leaf blade length, leaf blade width, initial leaf angle, specific leaf weight and deformation coefficient on leaf space shape. Then the equation was solved with parameterization. The sensitivity analysis showed that the equation could well reflect the integrated effects of leaf length, leaf width, specific leaf weight and leaf deformation coefficient, consistent with rice plant architecture in practice.
A field experiment was conducted at the Nanjing Agricultural University for validating the equation. Two cultivars (SU63 and WYG7) were nursed in dry-bed on May 20, and transplanted on June 20 with single seedling. Water and nutrients were supplied according to high yielding rice management. At jointing and booting stage of rice, the 3-dimension coordinates of several points in leaf midrib were measured with the 3D digitizer, and at the same time leaf blade length, width, initial leaf angle were obtained. Then simulation analyses were conducted on the equation with the experiment data. The results indicated that the leaf curvature equation could reasonably and reliably describe the change pattern of leaf shape characteristics of rice under different conditions.
The leaf curve equation could dynamically simulate the space shape of leaves with different initial leaf angles and special leaf weights by reduced parameters of rice leaf, especially in modeling day-to-day crop growth.

Key words: Rice, Leaf shape, Leaf curvature, Quantitative modeling, Virtual crop