Cell walls were prepared from cultured mesophyll cells of Zinnia elegans L. that were transdifferentiating into tracheary elements and incubated in a buffer to undergo autolysis. The rate of autolysis of cell walls was determined by measuring the amount of carbohydrate released from the cell walls into the buffer during incubation. During the course of culture of mesophyll cells, the autolysis rate increased markedly at the time when thickenings of secondary cell walls characteristic of tracheary elements became visible (after 48-72 h of culture), and thereafter the rate remained at a high level. Comparative studies on the autolysis rate of cell walls using various control cultures, in which tracheary element differentiation did not take place, revealed a close relationship between the autolysis rate around the 60th hour of culture and differentiation. Sugar analysis by colorimetric assays and gas chromatography of carbohydrates released from the cell walls detected uronic acid, arabinose, galactose, glucose, xylose, rhamnose, fucose, and mannose. Among these sugars, uronic acid was the most abundant, and accounted for approximately half of the total released sugars. The decrease of acidic polysaccharides in the primary cell walls during tracheary element differentiation was visualized by staining cultured cells with alcian blue at pH 2.5. These results suggest that active degradation of components of primary cell walls, including pectin, is integrated into the program of tracheary element differentiation.

Twenty cultivars were grown in paddy fields seven times from 2008 to 2010. The percentage of cracked grains was positively correlated with the temperature during the early stage of grain filling. Among the cultivars used, Futaba, Yamahikari and Fujisaka 5 showed high percentages of cracked grains. Cultivars Hananomai, Hanaechizen, Nikomaru and Himenomai showed high percentages of grain cracking when the temperature during grain filling was high although cracks were scarcely formed when it was low. On the other hand, Chinese cultivar Yan Xuang 203 showed stably lower percentages of cracked grains under higher temperature conditions. In the pot experiments conducted in 2009, the temperature conditions after the heading stage were identical for all cultivars and high temperature treatment was given during the early stage of grain filling. In this experiment, the percentage of cracked grains was significantly lower in Yan Xuang 203 than in the other cultivars. We concluded that Yan Xuang 203 is highly resistant to grain crack formation even when the air temperature during the grain filling stage is high.

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A newly developed early maturing and high palatability rice cultivar Tsukiakari has been disseminated in the Hokuriku region. It showed 10% higher grain yield than an early maturing rice cultivar Akitakomachi. This study aimed to clarify the highyielding characteristics of Tsukiakari through the multi-environmental testing in the Hokuriku region. A total of 47 yield trials during 2017 -2019 revealed that the grain yield of Tsukiakari reached a plateau around 750 g m -2 . From the significant linear regression among grain yield, yield components, and shoot nitrogen content in Tsukiakari, the values obtained were 35,700 spikelets per square meter, 423 panicles per square meter, 83.8% of filled grains, 25.1 g of one-thousand grains, and 14.0 g m -2 of shoot nitrogen content at a grain yield of 750 g m -2 . The percentage of perfect grains and grain protein content was estimated to be 72.5% and 7.1% at a grain yield of 750 g m -2 using the significant linear regression with spikelet number per square meter, which was developed using the data set obtained in 2017 -2018 and 2017 -2019, respectively. Note that the percentage of perfect grains in 2019 was much lower than that in 2017 -2018 due to an extremely high temperature during ripening. Calculated culm length of Tsukiakari at a grain yield of 750 g m -2 was 80.4 cm, and it is expected to avoid lodging at maturity up to approximately 80 cm. Overall results indicate that Tsukiakari is an elite cultivar that can achieve high yield and grain quality without lodging if rice plants are not subjected to an extremely high temperature during ripening.