Submitted to: American Society of Plant Biologists Annual Meeting
Publication Type: Abstract Only
Publication Acceptance Date: August 4, 2006
Publication Date: August 9, 2006
Citation: Deridder, B.P., Crafts-Brandner, S.J., Salvucci, M.E. 2006. Warm Root Temperature Mitigates the Effect of Chilling in the Dark on Photosynthesis in Cotton (Gossypium hirsutum) Seedlings. American Society of Plant Biologists Annual Meeting. P09005. Available: http://abstracts.aspb.org/pb2006/public/cgi-bin/search.cgi Technical Abstract: Productivity of warm season crops such as cotton (Gossypium hirsutum L.) can be reduced by untimely episodes of chilling temperature that often occur during the first weeks after planting. We examined the impact of chilling stress on cotton seedlings two weeks after planting by chilling both shoots and roots, or only shoots, to 10 ºC for three consecutive nights while maintaining normal daytime temperature (28 ºC). Compared to the control, seedlings with shoots and roots chilled for 3 nights exhibited greatly reduced photosynthetic rates correlated with a 25% reduction in dry-weight. In contrast, when only the shoots were chilled, photosynthetic rates were only moderately reduced and dry matter accumulation was similar to the control. Upon return to control temperature conditions, growth rate of seedlings with chilled roots and shoots remained lower than that of control seedlings or seedlings with chilled shoots/warm roots. Examination of photosynthetic indicators revealed a stomatal limitation to carbon assimilation (CER) shortly following the overnight chill. Upon re-warming, inhibition of CER persisted despite normal leaf water status and was associated with non-stomatal effects. Assessment of antioxidant defense mechanisms and chlorophyll fluorescence failed to support photoinhibitory limitations to CER. Considerable differences were observed between all treatments with respect to free amino acid levels in leaf tissue. The results of this study suggest normal root temperature maintained during a dark chill may mitigate the effects of shoot chilling on photosynthesis in cotton and affect the accumulation of free amino acid pools in leaves.