Studies on the development of various parts of paddy rice plant of 1st crop in Okinawa. 1. Relation of elongation and dry weight of the organs of the top of the rice plant.

In Okinawa, the 1st crop of rice is sown when it is cool and harvested when it is warm and long-day, and the 2nd crop seeding is practiced during warm season and it matures when it is cool and short-day. It is an interesting problem in relation to low productivity of the 2nd crop, to clearly the developmental characteristics of the crop happend is such quite contrary climatic conditions. This paper as a part of "Studies on the development of various parts of paddy rice plant of 1st crop, is on the elongation processes and the changes of dry weight of organs of the rice plant, i. e., leaf-blades, leaf-shehths, internodes, panicles, etc. 1. The elongation processes of leaf-blades, leaf-sheaths, internodes, and panicle show S-shape curve. The elongation of a blade is later than that of the sheath for one blade's emergence period. The panicle elongates together with the sheath of the boot-leaf (Fig. 1, Table 3). 2. Leaf-blades and sheaths grow longer as the leaf order goes up, until the turning period of leaf appearance cycle at which the plant reaches to the period of the highest activity of elongation. Those emerge during the period show maximum growth in length. The leaves which emerge after the ear differentiation time become gradually shorter, and the periods of their elongation become longer (Fig. 1). 3. As to the living period of the leaf on the main stem, the lower ones up to the 10th leaf have short periods and the higher ones above the 11th one have long period. Two or three leaves at the top of the stem continues to live up to the harvest time (Table 4). 4. As to the increase and decrease processes of dry weight, there are great differences between the lower leaf group (1st to 10th leaf) and the upper leaf group (11th to the 15th). The one among the lower group has a maximum dry weight before the ear differentiation time, and the movement of nutrient elements occurs mainly about the ear formation time. The leaf among the upper group has a maximum dry weight at the heading time, and the translocation of elements occurs after the heading time and the quantity of translocated materials is greater (Fig. 2, Fig. 3). 5. As to the relative quantity of translocated material from the leaf-sheath, those which increase dry weight during tillering period have higher quantities than the 10th leaf-sheath which shows the highest activity of weight increase during the ear formation time and has the least translocated material. Those upper than the 10th leaf-sheath have also higher translocated materials. But it is very small in upmost leaf-sheaths which are alive when other lower ones are dead (Table 6). It is considered that the relative quantity of translocated materials is high in the leaf-sheath which increases dry weight in tillering period is due to the pecuriality of the growth of the first crop and the characteristics of Taichu No. 65. 6. As to the relation between the elongation of organs and the increase of dry weight, an increase of dry weight generally begins around when the speed of elongation of the organ becomes greatest, and the maximum dry weight is reached around when the elongation completes. But the rate of dry weight increase in the leaf which increases dry weight during the formation and elongation of the ear and the elongation of lower internodes is lower (Fig. 4). There are close relations between the formation and elongation of organs and the increase and translocation of nutrient elements