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Dive into the research topics where T. A. Gunawardena is active.

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Featured researches published by T. A. Gunawardena.


Crop & Pasture Science | 2003

Low temperature induced spikelet sterility in rice. I. Nitrogen fertilisation and sensitive reproductive period

T. A. Gunawardena; S. Fukai; F. P. C. Blamey

Low temperature during panicle development in rice increases spikelet sterility. This effect is exacerbated by high rates of nitrogen (N) application in the field. Spikelet sterility induced by low temperature and N fertilisation was examined in glasshouse experiments to clarify the mechanisms involved. In two glasshouse experiments, 12-h periods of low (18/13degreesC) and high (28/23degreesC) day/night temperatures were imposed over periods of 5-7 days during panicle development, to determine the effects of low temperature and N fertilisation on spikelet sterility. In one experiment, 50% sunlight was imposed together with low temperature to investigate the additive effects of reduced solar radiation and low temperature. The effect of increased tillering due to N fertilisation was examined by a tiller removal treatment in the same experiment. Pollen grain number and spikelet sterility were recorded at heading and harvest, respectively. Although there was no significant effect of low temperature on spikelet sterility in the absence of applied N, low temperature greatly increased spikelet sterility as a result of a reduction in the number of engorged pollen grains per anther in the presence of applied N. Spikelet sterility was strongly correlated with the number of engorged pollen grains per anther. Low temperature during very early ( late stage of spikelet differentiation-pollen mother cell stage) and peak ( second meiotic division stage-early stage of extine formation) microspore development caused a severe reduction in engorged pollen production mainly as a result of reduced total pollen production. Unlike low temperature, the effect of shading was rather small. The increased tillering due to application of high rates of N, increased both spikelet number per plant and spikelet sterility under low temperature conditions. The removal of tillers as they appeared reduced the number of total spikelets per plant and maintained a large number of engorged pollen grains per anther which, in turn, reduced spikelet sterility. The number of engorged pollen grains per anther determined the numbers of intercepted and germinated pollen grains on the stigma. It is concluded that N increased tillering and spikelet number per plant and this, in turn, reduced the number of engorged pollen grains per anther, leading into increased spikelet sterility under low temperature condition.


Crop & Pasture Science | 2003

Low temperature induced spikelet sterility in rice. II. Effects of panicle and root temperatures

T. A. Gunawardena; S. Fukai; F. P. C. Blamey

Low temperatures impose restrictions on rice (Oryza sativa L.) production at high latitudes. This study is related to low temperature damage that can arise mid-season during the panicle development phase. The objective of this study was to determine whether low temperature experienced by the root, panicle, or foliage is responsible for increased spikelet sterility. In temperature-controlled glasshouse experiments, water depth, and water and air temperatures, were changed independently to investigate the effects of low temperature in the root, panicle, and foliage during microspore development on spikelet sterility. The total number of pollen and number of engorged pollen grains per anther, and the number of intercepted and germinated pollen grains per stigma, were measured. Spikelet sterility was then analysed in relation to the total number of pollen grains per spikelet and the efficiency with which these pollen grains became engorged, were intercepted by the stigma, germinated, and were involved in fertilisation. There was a significant combined effect of average minimum panicle and root temperatures on spikelet sterility that accounted for 86% of the variation in spikelet sterility. Total number of pollen grains per anther was reduced by low panicle temperature, but not by low root temperature. Whereas engorgement efficiency ( the percentage of pollen grains that were engorged) was determined by both root and panicle temperature, germination efficiency (the percentage of germinated pollen grains relative to the number of engorged pollen grains intercepted by the stigma) was determined only by root temperature. Interception efficiency (i.e. percentage of engorged pollen grains intercepted by the stigma), however, was not affected by either root or panicle temperature. Engorgement efficiency was the dominant factor explaining the variation in spikelet sterility. It is concluded that both panicle and root temperature affect spikelet sterility in rice when the plant encounters low temperatures during the microspore development stage.


Crop & Pasture Science | 2005

The interaction of nitrogen application and temperature during reproductive stage on spikelet sterility in field-grown rice

T. A. Gunawardena; S. Fukai

Increased grain yield in response to high rates of application of nitrogen (N) fertiliser is often limited by increased spikelet sterility, particularly under low temperature conditions in the New South Wales (NSW) rice industry. In 3 field experiments, different N rates were applied for different sowing dates to investigate the interaction between N rate and temperature during microspore development on spikelet sterility and grain yield. In one experiment the effect of water depth on spikelet sterility was also investigated. Engorged pollen production, spikelet sterility, and yield and its components were recorded. Application of N affected a few different processes that lead into spikelet sterility. Application of N at both pre-flood (PF) and panicle initiation (PI) significantly reduced the number of engorged pollen grains per anther, which was negatively correlated with spikelet sterility. Application of N and low temperature during microspore development with the absence of deep water also decreased pollen engorgement efficiency (the percentage of pollen grains that were engorged). Application of N further increased spikelet density, which, in turn, increased both spikelet sterility and grain yield. The combined effect of spikelet density and low temperature during microspore development explained the 44% of variation in the number of engorged pollen grains per anther. Grain yield was decreased by low temperature during microspore development in the shallow water when N was applied. Spikelet sterility as a result of late sowing was strongly correlated with minimum temperature during flowering. It is concluded that N application reduced pollen number per anther as a result of increased spikelet density, and this made the spikelets more susceptible to low temperature, causing increased spikelet sterility.


Seed Science and Technology | 2005

Seed treatment with gibberellic acid and glycinebetaine improves seedling emergence and seedling vigour of rice under low temperature

D. Chen; T. A. Gunawardena; B. P. Naidu; S. Fukai; J. W. M. Basnayake


4th International Crop Science Congress | 2004

The effects of nitrogen application and assimilate availability on engorged pollen production and spikelet sterility in rice

T. A. Gunawardena; S. Fukai


4th International Crop Science Congress | 2004

Expression of genotypic responses to frost tolerance in wheat

T. A. Gunawardena; P.N. Bodapati; S. Fukai


IREC Farmers' Newsletter, Rice R & D Edition | 2003

Increasing cold tolerance in rice

P.N. Bodapati; T. A. Gunawardena; S. Fukai


10th Australian Agronomy Conference | 2001

Nitrogen decreases deep irrigation efficacy in reducing low temperature damage in rice

T. A. Gunawardena; S. Fukai; F. P. C. Blamey


Solutions for a better environment: Proceedings of the 11th Australian Agronomy Conference, Geelong, Victoria, Australia, 2-6 February 2003. | 2003

Assessing the likelihood of the occurrence of low temperature damage in the NSW rice industry.

T. A. Gunawardena; S. Fukai; F. P. C. Blamey


3rd Interantional Temperate Rice Conference | 2003

Warm root can mitigate low temperature induced spikelet sterility

T. A. Gunawardena; S. Fukai

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S. Fukai

University of Queensland

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T. C. Farrell

University of Queensland

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