Poster: Global change

Abs # 21: Temperature sensitivity of pollen viability and seed-set of grain-sorghum (Sorghum bicolor L.) is adversely affected by growth at elevated carbon dioxide

Presenter:	Prasad, P.V. Vara , vpaga@mail.ifas.ufl.edu
Authors	Prasad, P.V. Vara  (A)   Boote, Kenneth J.  (A)   Allen, Jr, L. Hartwell  (B)
Affiliations:	(A): University of Florida, Agronomy Department (B): USDA-ARS, Gainesville

Global climate change, especially increases in temperature and carbon dioxide (CO₂), will have significant impacts on crop seed yields. Pollen viability and seed-set are important factors governing yields which are highly sensitive to temperature. Objectives of our research were to (a) quantify the impact of elevated temperature on pollen viability and seed-set of grain-sorghum at ambient and double ambient CO₂; and (b) determine if the temperature sensitivity of pollen viability and seed-set was influenced by elevated CO₂. Plants of cv. DK28E were grown at temperatures of 32/22, 36/26, 40/30 and 44/34 C at ambient (350 μmol mol^-1) and elevated (700 μmol mol^-1) CO₂ from emergence to maturity. Panicles were tagged at emergence and characteristics of pollen germination were determined at anthesis. The total numbers of filled and unfilled florets from tagged panicles were counted at maturity to estimate seed-set. Pollen grains from various treatments were collected and their ability to germinate at temperatures ranging from 10 to 45 C was determined to estimate cardinal temperatures. There was no panicle emergence at 44/34 C at either ambient or elevated CO₂. Growth temperature of 36/26 C significantly decreased pollen viability and seed-set (proportion of total florets setting seeds) compared to 32/22 C. The perecentage decrease in pollen viability and seed-set at 36/26 C was greater at elevated CO₂ when compared to ambient CO₂. Seed-set at elevated CO₂ compared with ambient CO₂ was significantly lower at both 32/22 and 36/26 C due to greater number of florets per panicle and lower pollen viability. There was no influence of elevated CO₂ on the cardinal temperatures (Tmin, Topt and Tmax) for pollen germination, which were 19, 30 and 39 C, respectively.