Submitted to: Journal of Experimental Botany
Publication Type: Peer reviewed journal
Publication Acceptance Date: 10/1/2004
Publication Date: 2/1/2005
Citation: Koti, S., Reddy, K.R., Reddy, V., Kakani, V.G., Zhao, D. 2005. Interactive effects of carbon dioxide, temperature and ultraviolet-b radiation on soybean (glycine max l.) flower and pollen morphology, pollen production, germination and tube lengths. Journal of Experimental Botany. 56(412):725-736. Interpretive Summary: The carbon dioxide concentration, temperatures and harmful Ultraviolet-B (UV-B) radiation reaching the earth surface are rising rapidly. It is important to evaluate the effects of these atmospheric variables associated with global climate change on crop growth and development. A study was conducted to evaluate the effects of these global change variables and their interactions on soybean crop. From this study it was observed that there are no beneficial interactions between carbon dioxide, temperature and UV-B radiation on soybean especially on the reproductive performance of soybean crops like pollen germination. Increase in temperatures and UV-B radiation levels alone, or in combination with carbon dioxide levels, altered pollen morphology and decreased pollen production. These results indicate a negative effect on fruit set and yield of soybean under the projected climates of the future. These findings will be highly useful for soybean breeders in developing new cultivars of the future. In addition, the variability among soybean cultivars in their response to changes in the environment will help in selecting soybean cultivars for yield increases in a warmer, high UV-B and higher carbon dioxide environments of the future.
Technical Abstract: Global climate change components such as carbon dioxide concentrations ([CO2]), temperatures (T) and ultraviolet-B (UV-B) radiation are continuously increasing. The objectives of this study were to determine the effects of season-long exposures of two [CO2] treatments [360 and 720 mmol mol-1 (+CO2)] at two temperature treatments [30/22 degrees C and 38/30 degrees C (+T)] and two UV-B radiation treatments [0 and 10 kJ m-2 d-1 (+UV-B)] on flower and pollen morphology, pollen production, germination and tube lengths of six soybean genotypes. Plants grown either at +UV-B or +T alone or in combination produced smaller flowers with smaller standard petal and staminal column lengths at both control and +CO2 conditions. The flowers from plants grown under +UV-B or +T alone, or in combination, produced less pollen with poor germination and shorter pollen tube lengths in vivo. Pollen produced in plants grown under +T, +UV-B, and +T+UV-B conditions, produced shriveled/collapsed pollen without apertures and with disturbed exine ornamentation even at +CO2 conditions. Based on cumulative stress response index (CSRI), the sum of the relative responses, the genotypes could be arbitrarily classified as tolerant (DG 5630RR, CSRI < 600), intermediate (D 88- 5320, D 90-9216, Stalwart III, PI 471938, CSRI 600 - 1100) and sensitive (DP 4933RR, CSRI > 1100). On the whole, there were no beneficial interactions between [CO2], temperature and UV-B radiation, and the results show possibilities of decreasing seed yields in the future climates. The differences in sensitivity identified among genotypes imply the options for selecting soybean genotypes with tolerance to environmental stresses of future climates.