Drought or Mechanical Stress Affects Broccoli Transplant Growth and Establishment but Not Yield

Abstract

Broccoli (Brassica oleracea L. Group Italica cv . Green Duke) seedlings were subjected to brushing with a piece of cardboard (40 strokes/min, 1 min twice daily), wind (7 m·s -1 for 5 min twice daily) or drought (visible wilt for 2 hours daily) treatments. Plant response to treatment was affected by seasonal or environmental conditions. All conditioning treatments reduced leaf dry weight and area, stem dry weight and length, and the total shoot and root dry weights in an experiment conducted in Sept. 1986 (Fall 1986). However, in experiments conducted the following year, broccoli transplants treated in March (Spring 1987) showed little response to the treatments, while transplants treated in August (Fall 1987) showed only a moderate response. In Fall 1986 and 1987, brushing improved field establishment as measured by the rate of shoot dry weight gain over the period of field establishment. Yield of the primary head of broccoli transplants treated in either Spring or Fall 1987 was not affected by the conditioning treatments. Brushing may provide an effective alternative to drought or plant growth retardants in conditioning broccoli transplants prior to field planting.