Strawberry Growth and Photosynthetic Responses to Paclobutrazol

Abstract

Foliar sprays of increasing concentrations (0, 75, 150, 300, 600, and 1200 mg·liter-1) of paclobutrazol were applied to `Cardinal' strawberry plants (Fragaria × ananassa Duch.) 35 days after transplanting. The plants were established in August in cultivated plots for measurement of paclobutrazol effects on first year growth or in a double-row hill system on black polyethylene-covered raised beds for 2nd year measurements. Increasing the paclobutrazol concentration reduced the number of runners, decreased runner length, and limited biomass partitioned into daughter plants. By the end of the first growing season, paclobutrazol had increased lateral crown development but reduced leaf area per treated plant. Root growth was reduced by concentrations >600 mg·liter-1. Treatment with 75 to 300 mg·liter-1 increased total plant dry weight by 33% to 46%. The following spring, plant growth was decreased by ≥ 300 mg·liter-1. Yield was increased by all treatments, except 1200 mg·liter-1. Leaf net photosynthesis increased within 12 days after treatment with paclobutrazol and was higher than in the controls the next summer. Leaf stomata1 conductance also increased the first year and was significantly higher the 2nd year after treatment. The optimum concentration of paclobutrazol for strawberries appears to be between 150 and 300 mg·liter-1.