ANALYSIS OF GRAVITY-INDUCED GROWTH-RESPON SE OF SHOOT IN RICE (ORYZA-SATIVA L) - RESPONSE OF LEAF PULVINUS, LAMINA JOINT AND TORSION OF LEAF SHEATH

Plants were grown in pots containing soil. Every tiller was cut off wh en it emerged and only the main shoots were allowed to grow. Exp. 1. P lants in pots were artificially placed horizontally and the bending de gree of lamina joints and pulvini was investigated. The artificial pla cement in the horizontal direction increased the bending degree of lam ina joint and pulvini. In the treatment in which pots were placed hori zontally and then turned upright, the bending degree of pulvini was de creased, but that of lamina joint was not changed. Exp, 2, The respons e direction of the torsion in the leaf sheath of rice placed horizonta lly was downward at a portion from the top to the center, while it was upward from the center to the bottom. Exp. 3. The leaf blade was part ly removed or added weight. The results suggested that the leaf blade weight influenced the degree of torsion. When the weight of the leaf b lade which was set sideways was released, the degree of torsion decrea sed. Exp, 4, In the temperature treatment, the low temperature decreas ed the torsion of the leaf sheath. This result suggested that the tors ion of leaf sheath physiologically influenced by the temperature. It s eems that the unit of ''pulvinus = leaf sheath = lamina joint'' was a response to gravity.