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Physiological Section

Mohammed, Abdul Razack [1], Rounds, Elliott W. [1], Tarpley, Lee [1].

Response of rice tillering to sub-ambient levels of ultraviolet-B radiation.

Low levels of ultraviolet-B (UV-B: 280-320 nm) radiation below the canopy in densely planted rice (Oryza sativa L.) fields have a negative impact on tiller initiation and development. Moreover, there is a varietal difference in the response to UV-B radiation in rice. The objective of this study was to examine the effects of UV-B radiation on rice physiology with special emphasis on tiller development of both the main and ratoon crops for three different rice cultivars: Cocodrie, Saber and CL-161. Rice plants were exposed to UV-B radiation of 0 (control), 8 (ambient), or 16 (twice ambient) kJ m-2 d-1 in Experiment I and 0, 4 (sub-ambient) or 8 kJ m-2 d-1 in Experiment II. Exposure was from 20 d after emergence to the early grain-filling stage (76 d after emergence), in a square-wave approach for 8 h from 0800 to 1600 h. The UV-B radiation intensity was checked daily with a UVX digital radiometer. Plant height, tiller number per plant, and chlorophyll content showed no significant (P>0.05) difference between cultivars at 8 and 16 kJ m-2 d-1. There was, however, a significant (P>0.05) difference between the control and ambient UV-B levels for tiller number per plant in Experiment I. Control plants were taller and had more chlorophyll content when compared to the UV-B treatments, but this difference was not significant. In the second experiment, there was no significant (P>0.05) difference between the control and UV-B treatments with respect to plant height and chlorophyll content for all three cultivars. There was, however, a significant (P>0.05) difference between the ambient and sub-ambient UV-B levels with respect to tiller number in Experiment II. Our results show that UV-B radiation plays an important role in tiller initiation and development. Partially supported by the Texas Rice Belt Warehouse and Texas Rice Research Foundation.


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1 - Texas Agricultural Experiment Station, TAMU Dept. Soil and Crop Sciences, 1509 Aggie Dr., Beaumont, Texas, 77713

Keywords:
rice
ultraviolet radiation
tillering.

Presentation Type: Oral Paper
Session: 7-7
Location: 408/Hilton
Date: Monday, August 15th, 2005
Time: 11:00 AM
Abstract ID:210


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