Changes in Leaf Stomatal Properties in Rice with the Growing Season

Transplanting rice varieties grown in different seasons can lead to different yields due to different dry matter production. Early-season rice varieties transplanted in the late season can obtain high yields with short-growth duration and higher yields driven by higher dry matter production. To make clear the variations in dry matter production across seasons, four early-season rice varieties were chosen for late-season transplantation. The grain yield, dry matter accumulation, leaf photosynthetic, and leaf stomatal properties were studied. It was observed that the average yields of these four varieties in the late season were 33% greater, despite a reduced growth period of 13 days in comparison with the early season. Furthermore, there was a notable increase in both total and post-heading dry matter production during the late season. The leaf net photosynthetic rate, stomatal area, stomatal width, and stomatal length were higher in the late season. Despite no significant difference in stomatal density between seasons, strong positive linear relationships were observed between net photosynthetic rate and stomatal conductance, and between stomatal conductance and area. These relationships demonstrate that the increase of the stomatal width and length of the leaves in the late season leads to an increase in the stomatal area, thereby increasing the stomatal conductance and enhancing the photosynthesis of the leaves. Consequently, this leads to greater dry matter production and a higher yield compared to the early season. Therefore, when breeding new high-yielding and short-growing varieties, the large stomatal area can be used as a reference index.