MATURITY OF APPLE CV ELSTAR AS AFFECTED BY TEMPERATURE DURING A 6-WEEK PERIOD FOLLOWING BLOOM

In two experiments under controlled conditions, the effect of temperat ure (16, 20 and 24 degrees C, experiment 1; 16 and 22 degrees C, exper iment 2) during a six-week period immediately following bloom on the p rogress of ripening around the normal picking time was evaluated for f ruits of cv. Elstar. After six weeks, the temperature in experiment 1 was kept at 20 degrees C throughout. In experiment 2 the temperature w as 22 degrees C from week 6 to 14, and 16 or 22 degrees C from week 14 to 22. Post-bloom temperature clearly affected the rate of fruit ripe ning as reflected in ethylene production, background colour, starch co ntent, firmness and red blush, but these variates did not respond to t he same degree. The effect of temperature late in the season on ripeni ng (just during the maturation period) was almost absent when the post -bloom temperature was 16 degrees C. However, when post-bloom temperat ure was 22 degrees C, fruits were greener, firmer, contained more star ch and showed more red blush at 16 than at 24 degrees C given from wee k 14 to 22. The acid content at ripening was lower at the higher post- bloom temperatures. Irrespective of the post-bloom temperature, acid c ontent was also reduced at the higher temperature given during the mat uration period. The content of soluble solids showed no consistent pat tern.