Rice Growth and Development

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1 – Rice Growth and Development Karen Moldenhauer and Nathan Slaton Rice is an annual grass (Figure 1-1) with round, hollow, jointed culms; narrow, flat, sessile leaf blades joined to the leaf sheaths with collars; well-defined, sickle-shaped, hairy auricles; small acute to acuminate or two cleft ligules (Figure 1-2); and terminal panicles. The life cycle of rice cultivars in Arkansas ranges from 110 to 150 days from germination to maturity, depending on the variety and the environment. Principle: Identification of plant parts is essential in differentiating rice plants from weeds. Rice plant growth can be divided into three agronomic stages of development: 1. vegetative (germination to panicle initiation); 2. reproductive (panicle initiation (PI) to heading); and 3. grain filling and ripening or maturation (heading to maturity – Figure 1-3). These stages influence the three yield components: 1) number of panicles per unit land area, 2) the average number of grain produced per panicle and 3) the average weight of the individual grains. These three components determine grain yield. The following descriptions and diagrams characterize the growth stages for rice plants. Vegetative Stage The vegetative growth stage is characterized by active tillering, a gradual increase in plant height and leaf emergence at regular intervals. The length of this stage primarily determines the growth duration of varieties. Some very-early maturing varieties have a shortened vegetative growth stage, while others have both shortened vegetative and reproductive growth stages. Panicle initiation (PI) may occur before the maximum tiller number is reached in very-short­ season and some short-season varieties. Heading in these varieties may be staggered due to later tillers which produce panicles. In midseason varieties, the maximum tiller number is reached and followed by a

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