Life Cycle and Morphological Characteristics of Weedy Rice (Oryza sativa Complex, Locally Called Padi Angin), a Noxious Weed of Ricefields in Malaysia

Abstract: Studies were conducted at the plant house and the laboratory at the School of Biological Sciences, Universiti Sains Malaysia (USM), Pulau Pinang to evaluate seed germination, seedlings establishment and growth patterns Oryza Sativa of (weedy rice). Weedy rice is rated as one of the most troublesome weeds in direct seeded fields in Malaysia. Evidently, there are 10 variants of weedy rice based on morphological characteristics. Morphological structures of weedy rice namely open panicle type, compact panicle type, and awn type were examined. The comparison using scanning electron microscope (SEM) did not show anatomical differences between weedy rice variants for both seed and leaf surfaces. However, the hair or tnchomes structures are clearly shown in awn type compared with other variants and Oryza Sativa (cultivated rice). Cultivated rice and all variants have stomata on both adaxial and abaxial leaf surface. However, more dense deposits of epicuticular waxes were found on the adaxial surface of a leaf compared with the abaxial surface. The result of growth pattern showed that the variants of weedy rice produce an abundance seeds, as high as 200-220 numbers of spikelets per panicle for awn type, 190-210 spikelets for open panicle type and 210-230 spikelets for compact panicle type. All variants complete their life cycles within 85-95 days after emergence.