Submitted to: Agronomy Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: November 9, 2000
Publication Date: N/A
Technical Abstract: Plant species of the genus Cuphea are known to produce seeds rich in medium chain fatty acids, which are valued as feed stock for industrial chemical manufacturing. Presently, efforts are being made to domesticate certain species of Cuphea for oilseed production. The objective of this study was to evaluate the photosynthetic performance of Cuphea (C. viscosissima x lanceolata) to long-term growth under low temperatures. This is part of a larger study to determine the feasibility of its production in the northern Corn Belt. Plants were grown to full maturity at 18/12 and 24/18 deg C day/night temperatures in environment-controlled chambers. Analysis of leaf CO2 assimilation versus internal [CO2] showed that plants grown at 18/12 deg C had both higher carboxylation efficiency and CO2-saturated rates of photosynthesis. On a leaf area basis, the chlorophyll a/b content was slightly less in leaves of plants grown at 18/12 deg C. However, total Rubisco activity was considerably higher than plants grown at 24/18 deg C. When exposed to short-term cold-induced photoinhibition at 10 deg C and 1500 PPFD, leaves of plants grown at 18/12 deg C consistently maintained greater photochemical efficiency of PSII and degree of "open" (i.e., oxidized) reaction centers. Increased photosynthetic capacity in leaves developed under the lower temperature regime, rather than nonphotochemical dissipation of excitation energy, was a primary reason for greater PSII efficiency under photoinhibitory conditions. Results indicate that Cuphea can acclimate to low temperatures and hence may be well adapted for production in the northern Corn Belt.