No abstract

Of 33 chemicals tested, 21 had no effect on net photosynthesis (Pn) or dark respiration (Rd) of apple (Malus pumila Mill.). Of the 12 having an effect, most reduced Pn, 2 increased Pn, and 1 increased Rd. Oil and emulsifiable concentrate formulations generally reduced Pn, while Plictran and formetanate hydrochloride increased Pn. In 1 test qxythioquinox increased Rd whereas other materials had little or no effect in any test. There was no difference in response by cultivar or to environment, but the method of treatment introduced wide variation in the effects of certain chemicals.