Graduate Thesis Or Dissertation

 

Biology of mudplantain (Heteranthera reniformis Ruiz et Pavon) and its control in flooded rice Public Deposited

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https://ir.library.oregonstate.edu/concern/graduate_thesis_or_dissertations/w3763b37w

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  • In CIAT, Centro Internacional de Agricultura Tropical, located in Palmira, Colombia, a series of experiments were conducted to study the biology and control of mudplantain (Heteranthera reniformis Ruiz et Pavon), a member of Pontederiaceae family. Mudplantain is a perennial aquatic plant which reproduces by both seeds and stolons. It is found in rice in some areas of Colombia, especially in thin rice stands, and is spreading rapidly because of its resistance to the traditional rice herbicides. The biological aspects studied were: (a) life cycle; (b) effect of light reduction on growth; (c) effect of water depth on growth; (d) germination requirements; and (e) vegetative propagation ability. The weed control experiments included the control of mudplantain in flooded rice planted with either pre-germinated or dry rice seed. The life cycle of mudplantain was observed in the field from 20 days after germination to 118 days later at 14-day intervals. It was found that fresh weight, number of nodes, number of leaves, number of capsules and length follow an approximate sigmoid curve. Capsules appear between the 48th and 62nd day after germination and their production increases progressively during the cycle. The effect of 0, 33, 53, 59, 79, 88, 96, and 100% light reduction on fresh weight, number of nodes, number of leaves, number of capsules, and capsule length observed 60 and 120 days after germination indicated that mudplantain is more adpated to grow under reduced light. Only when light is reduced by more than 75% is growth seriously inhibited. Seed germination decreased when light intensity was reduced by 88% or more. The effect of 0, 5, 10, 15, and 20 cm water depths on mudplantain growth was determined in plants in the 3- and 10-leaf growth stages. Younger seedlings were more affected by water depth. However, a depth of 5 cm was the most favorable, while lower or higher depths reduced growth. This shows why mudplantain is adapted to grow in flooded rice and that it would be impossible to control mudplantain by flooding since the rice would not tolerate more than 10 cm of water in the initial stages and the weed is not killed by this or greater water depths. Results of germination trials indicated that seeds germinate only under light and that light intensity controls total germination. Light, however, had to be combined with alternating da.y/night temperatures to stimulate germination. Moist or dry chilling as well as scarifying with sandpaper or sulfuric acid, or soaking the seeds did not promote germination under dark conditions nor improve germination under light. Seed germination was affected by germination media and seeding depth. Water gave the highest germination followed by puddled soil, and then by moist soil. Seeding at soil depths greater than one centimeter prevented germination. The vegetative propagation studies demonstrated that mudplantain propagates by stolons. Regrowth ability, however, was higher for stolons with leaves and low for stolons without leaves regardless of whether or not the roots had been removed. Control studies in flooded rice showed that mudplantain generally exhibits a great resistance to herbicides. Only butachlor (2-chloro- 2', 6-diethyl-N-(butoxymethyl) aceta.nilide) at 2. 5 kg ai/ha and oxadiazon (2 -tertiobuty1-4 -(2 , 4-dichloro-s -is o -propyl-oxyphenyl) 5-oxo - , 3,4-oxadiazoline) at 1.0 kg ai/ha in he dry-seeded rice experiment gave excellent control. The best control can be obtained by a rapidly established, dense rice stand growing under optimum conditions for pre-germinated rice. A dense stand and the use of chemicals is recommended for dry-seeded rice.
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