| Reproductive and vegetative responses of three strawberry (Fragaria x ananassa) cultivars ('Pocahontas', 'Raritan', and 'Sparkle') were studied under two sets of conditions: constant temperatures (15 and 30(DEGREES)C) at 8 hr photoperiod and varying day/night temperatures (20/10, 30/20, and 40/30(DEGREES)C) at 16 hr photoperiod.;At the varying day/night temperatures, fruit set, the size and total soluble solids of the berries were reduced by increasing the growth temperature. The leaf area, final length and width of the middle leaflets, length of the petioles, and fresh and dry weights of the leaves were reduced by increasing the growth temperature to 40/30(DEGREES)C. The number of leaves produced per plant were more at 30/20(DEGREES)C than the other two temperatures. The different cells composing the leaf blade and the epidermal cells of the petiole were reduced in size by increasing the growth temperature to 40/30(DEGREES)C. The proportion of epidermis in the leaf sections was not affected by the growth temperature; whereas the mesophyll proportion was increased and the intercellular space was decreased by increasing the growth temperature to 40/30(DEGREES)C. Shoot growth was much reduced by increasing the growth temperatures compared to the roots.;Increasing the growth temperature from 20/10 to 40/30(DEGREES)C had increased the acquired heat tolerance of plants as measured by the increased time to cause 50% electrolyte leakage in the cells and the reduce leakage rate. Increased growth temperature also increased the apparent number of molecular events to induce leakage.;Comparing the reproductive responses of the three cultivars to high temperatures, 'Pocahontas' was less sensitive to high temperatures, followed by 'Sparkle', and 'Raritan' was the least sensitive as was suggested. On the other hand, ranking the three cultivars based on their vegetative response to high temperature was not consistent and depended on the growth parameter used.;The time to first flowering was hastened, the number of secondary and tertiary flowers produced per plant, and the fertility of the pollen grains were reduced by increasing the growth temperature from 15 to 30(DEGREES)C. No such effect was noticed on the number of inflorescences produced, the number of primary flowers produced, nor the total heat units accumulated to the date of first flowering. Leaf area, length, and width of the middle leaflets, length of the petiole and the number of leaves produced per plant were increased by elevating the growth temperature to 30(DEGREES)C. |
