Leaf area and leaf area components analyses of wet sown rice and transplanted rice

On-farm experiment was conducted during the wet season from September 1995 to February 1996. A rice cultivar "Chieng Phatthalung" was used in this study. Plant density in wet sown rice was about 400 plants 1/square m and hill spacing in tranplanted rice was approximately 16-20 hills 1/square m. Rate of nitrogen fertilizer application was 75 kg N 1/ha. The results indicated that most of relationships between the leaf area and leaf area components of both planting methods showed positive correlation at the 0.001 probability level. No correlation was found in number of culms 1/square m (NCM2) vs leaf area 1/square m (LAM2), leaf size (LSIZE) vs number of leaves 1/square m (NLM2) in the wet sown rice and number of leaves 1/culm (NLC) vs NCM2 in the both planting methods. LSIZE vs NCM2 showed negative correlation in the wet sown rice, but a positive correlation in the transplanted rice. The average of leaf area and its components at various growth stages showed that LAM2, NLM2 and NCM2 at the beginnings of tillering and stem elongation in the wet sown rice were higher than those in the transplanted rice. In contrast, NLC and LSIZE at the beginning of tillering were lower in the wet sown rice. There was no significant difference in NLC between planting methods at the beginning of stem elongation and LSIZE at this growth stage was greater in the wet sown rice due to the delaying of stem elongation. The wet sown rice, therefore, had a longer duration for NLC and LSIZE formations than that in the transplanted rice. At the later growth stage of 50 percent flowering, LAM2 and NLC of the both planting methods were not different, while NLM2 and NCM2 were higher but LSIZE was lower in the wet sown rice. The patterns of growth in leaf area and leaf area components as a function of thermal time after sowing until the 50 percent flowering in each planting method could be explained by mathematical functions of time. These are decribed as follows: LAM2 increases in a logistic function, NCM2 increases during the tillering in a linear regression and after that it decreases in a negative logistic type of curve, NLC and LSIZE both increase in linear regressions throughout the growing period.