Abstract
ABSTRACTLeaf erectness is an important agronomic trait for improving canopy photosynthesis in rice. It is well known that leaf inclination angle (LIA) decreases after expansion during ripening. However, the high-yielding indica cultivar ‘Takanari’ retains a greater LIA during ripening than the high-quality japonica cultivar ‘Koshihikari’. To clarify the cause of the cultivar difference in LIA, we investigated anatomical characteristics of the lamina joint of a flag leaf. We found a close linear correlation between LIA at the centre and at the base of the leaf blade in both cultivars during ripening. The length of the lamina joint increased significantly more on the adaxial side of a leaf (the margin of the collar) than on the abaxial side (the abaxial side of the central part of the collar) in ‘Koshihikari’ after leaf expansion, but there was no clear difference in ‘Takanari’. We found a close linear correlation between the ratio of lamina joint length on the adaxial to abaxial sides and LIA in ‘Koshihikari’ and ‘Takanari’ during ripening. In ‘Koshihikari’, the average length of cells on the adaxial side increased significantly after leaf expansion, with no significant increase in that on the abaxial side and no significant change in cell number on either side. In ‘Takanari’, cell length and cell number showed no significant changes on either side of the lamina joint. We conclude that the cultivar difference in LIA during ripening is caused mainly by cell elongation on the adaxial side of the lamina joint.List of Abbreviations: k: light extinction coefficient; LIA: leaf inclination angle; QTL: quantitative trait locus
Highlights
Improving rice production to meet the needs of the growing global population is a major challenge in rice breeding (Kubo & Purevdorj, 2004)
Plant architecture is crucial to the efficiency of photosynthesis, and its manipulation is a feasible approach to increasing canopy photosynthesis and crop production per unit land area (Hall, 1993; Kumura, 1995; Li, Paterson, Pinson, & Stansel, 1999)
The relationship between leaf inclination angle (LIA) at the centre and at the base of the leaf blade was linear (1:1) at both full heading and 3 weeks after full heading (Figure 1). These results indicate that the LIA of the flag leaf is determined at the base of the leaf blade
Summary
Improving rice production to meet the needs of the growing global population is a major challenge in rice breeding (Kubo & Purevdorj, 2004). ‘Takanari’, the highest yielding indica cultivar in Japan, has a higher net assimilation rate after heading and produces more dry matter and grain yield than other Japanese cultivars owing to its erect leaves, small k value, and high individual photosynthetic rate (Takai et al, 2006; Taylaran, Adachi, Ookawa, Usuda, & Hirasawa, 2011). ‘Koshihikari’, an elite japonica cultivar, produces high-quality rice and is widely grown in Japan, but its LIA and leaf photosynthetic rate are not as large and its grain yield is not as high as those of ‘Takanari’ (Taylaran et al, 2011). These two cultivars offer the opportunity to study varietal differences in LIA. We conducted this study to investigate the differences in the LIA of the flag leaf between ‘Koshihikari’ and ‘Takanari’ following full expansion and to examine the causes of the difference from full heading to the end of ripening through anatomical examinations of the lamina joint
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