2008 Volume 77 Issue 1 Pages 13-21
Percentage of dying rachis branches and ripened grains of rice plant exposed to salty winds due to typhoon no. 15, 2004 in the Shonai area of Yamagata prefecture was investigated, to evaluate the effect of salty wind on the yield and quality of the rice plant and mechanism of the yield decrease. Percentage of dying rachis branches increased with an increasing amount of salt adhesion per panicle up to 1mg NaCl/panicle. Percentages of ripened grains and whole grain decreased with an increasing percentage of dying rachis branches. On the other hand, protein content of brown rice tended to increase with an increasing percentage of dying rachis branch. Weight of brown rice per unit area tended to decrease with an increasing percentage of dying rachis branches. In contrast, rice screening weight per unit area tended to increase with an increasing percentage of dying rachis branches. Weight of brown rice was"Sasanishiki">"Haenuki">"Koshihikari". Weight of brown rice per unit area was significantly correlated with rice screening weight and the rate of grains distribution with a (>1.9mm) thickness. In contrast, the weight of brown rice per unit area was not correlated with the number of spikelets per unit area. The yield of rice plants suffering from salty wind damage was reduced by the following factors. (a) adhesion of salt to the panicle, (b) occurrence of dying rachis branch, and (c) occurrence of incompletely filled gains or rice screenings, resulting in the reduction of brown rice weight. The rate of yield decrease was estimated from relationship between weight of brown rice and percentage of dying rachis branch. Even at the same percentage of dying rachis branches, it was higher in “Haenuki” than in “Sasanishiki”. Thus the equation of relationship between the weight of brown rice and percentage of dying rachis branches was separated into 2 lines. These results suggested that the rate of yield decrease was affected by the percentage of ripened grains more greatly than the number of days after heading when attacked by a typhoon.
