INFLUENCE OF SUPRAOPTIMAL ROOT-ZON E TEMPERATURES ON RUBISCO ACTIVITY, CHLOROPHYLL AND CAROTENOID LEVELS IN `ROTUNDIFOLIA' HOLLY

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  • 1 Department of Horticulture, Coastal Plain Experiment Station, Tifton, GA 31793
  • | 2 Department of Horticulture and Landscape Architecture, University of Kentucky, Lexington, KY 40546

High root-zone temperatures have been shown to affect photosynthate partitioning, respiration, nitrogen nutrition and growth of `Rotundifolia' holly. The loss of chlorophyll and protein in shoots of other plants in response to high root-zone temperatures has been documented. Therefore, the objectives of this research were to look at the effects of supraoptimal root-zone temperatures on RUBISCO activity, leaf protein and photosynthetic pigment levels.

Soluble protein levels in leaves increased linearly as root-zone temperature increased from 30 to 42 C. RUBISCO activity per unit protein and per unit chlorophyll responded quadratically to root-zone temperatures. Total chlorophyll, chlorophyll a & b, and carotenoid levels decreased linearly with increasing root-zone temperature. It is possible that `Rotundifolia' holly was capable of redistributing nitrogen to maintain RUBISCO activity for photosynthesis.

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