Scott A. Holaday
Photosynthetic Carbon Metabolism
- Ph.D., Botany, University of Florida (1978)
- M.S., Forestry, University of Florida (1973)
- B.S., Forestry, University of Illinois (1971)
My laboratory has spent over 20 years studying the effects of environmental stress (chilling, drought, heat) on primary metabolism, with an emphasis on photosynthesis. Studying cotton plants that over-express a gene indirectly linked to cellulose synthesis, a Ph.D. student of mine has recently discovered what may be an important method for improving water conduction in the root and stem of cotton. An increase in the supply of water to leaves, especially during a drought, would enhance photosynthetic activity that would be supplying carbohydrate to the developing bolls. Also, leaf senescence would be reduced and plants could grow larger, as we have observed. More water to the bolls would improve their ability to metabolize the carbohydrate that they receive and improve fiber growth, leading to a greater fiber yield, as has occurred in our experiments.
A second project involves the study of the physiological bases for why nitrogen enrichment of wetlands facilitates their invasion by certain non-native species. The study focuses on the invasive grass, Phalaris arundinacea, and the sedges in the genus, Carex, that are often displaced by P. arundinacea. A high photosynthetic rate is important for the competitive success of P. arundinacea, and it allocates a high proportion of its leaf nitrogen to photosynthetic proteins. Under nitrogen deprivation, it allocates much less nitrogen to photosynthesis and becomes a poor competitor. A more conservative approach is taken by Carex stricta that allocates a moderate proportion of its leaf nitrogen to photosynthesis when nitrogen is readily available. However, when it experiences nitrogen deprivation, it will maintain its nitrogen in photosynthesis for a couple of months. What controls these allocation differences and whether other species of Carex are closer to P. arundinacea in terms of leaf nitrogen allocation will require molecular and physiological analyses. A position for a master's student to work on this project is now available.
- Singh, B., L. Haley, J. Nightengale, W.-H. Kang, C.H. Haigler, and A.S. Holaday. 2005 Long-term night chilling of cotton, Gossypiumhirsutum, does not result in reduced CO2 assimilation. Funct. Plant Biol. 32:655-666.
- Kornyeyev, D., B.A. Logan, R.D. Allen, and A.S. Holaday. 2005.Field-grown cotton plants with elevated activity of chloroplastic glutathione reductase exhibit no significant alteration of diurnal or seasonal patterns of excitation energy partitioning and CO2 fixation. Field Crops Res. 94:165-175.
- Hozain, M.I., M.E. Salvucci, M. Fokar, and A.S. Holaday. 2010. The differential response of photosynthesis to high temperature for a boreal and temperate Populus species relates to differences in Rubisco activation and Rubisco activase properties. Tree Physiol. 30:32-44.
- Kornyeyev, D., B.A. Logan, and A.S. Holaday. 2010. Excitation pressure as a measure of the sensitivity of photosystem II to photoinactivation. Funct. Plant Biol. 37:943-951.
- He, Z., L.P. Bentley, and A.S. Holaday. 2011. Greater seasonal carbon gain across a broad temperature range contributes to the invasive potential of Phalaris arundinacea L. (Poaceae, reed canary grass) over the native sedge, Carex stricta LAM. (Cyperaceae). Amer. J. Bot. 98:20-30.
- Hozain, M.I., H. Abdelmageed, J. Lee, M. Kang, M. Fokar, R. D. Allen, and A. S. Holaday. 2012. Expression of AtSAP5 in cotton up-regulates putative stress-responsive genes and improves the tolerance to rapidly developing water deficit and moderate heat stress. J. Plant Physiol. 169:1261-1270.