The effect of indoleacetic acid and 2, 4-dichlorophenoxyacetic acid on the ripening of intact mature-green pears (Pyrus communis var. Bartlett) was investigated using a vacuum infiltration technique.The effects of indoleacetic acid and 2, 4-dichlorophenoxyacetic acid at concentrations of 0.01, 0.1, and 1.0 mM each were studied on softening, degreening, and on ethylene and C02 evolution. Softening and degreening were inhibited increasingly in response to increased concentrations of indoleacetic acid.This inhibitory property was amplified by 2 ,4-dichlorophenoxyacetic acid at concentrations comparable to those of indoleacetic acid. Application of the auxins also prevented the climacteric rise in respiration, but stimulated ethylene synthesis. Despite the presence of elevated ethylene levels, the inhibitory auxin effect was predominant.It is proposed that endogenous auxins in fruit represent a resistance factor in ripening and must be inactivated before ripening can occur.It was proposed that endogenous factors in fruit resist the action of ethylene in the promotion of ripening (14). Auxins are among the naturally occurring constituents in fruit which could function as resistance factors in ripening (16). Consequently, it was suggested by Frenkel (9) that the decline in the level of auxins concomitant with ripening is required to sensitize fruit tissue to the action of ethylene gas. In order to verify the role of auxin as a resistance factor in ripening, the authors studied changes in ripening and in CO2 and ethylene evolution in Bartlett pears in relation to applied auxins. The results of this study indicate that auxin could overcome the action of ethylene and inhibit ripening in Bartlett pear.MATERIALS AND METHODS Pears (Pyrus communis var. Bartlett) at the mature green stage were obtained from the pear orchard of Rutgers University, New Brunswick, New Jersey. The fruits were treated with 10 jul/l ethylene for 12 hr at room temperature prior to auxin application.Solutions containing IAA or 2, 4-D were applied to the fruit by a modified vacuum infiltration procedure (10). Intact fruits were punctured through the central cavity from the calyx end with a 20-gauge needle and were submerged in the infiltration solution. Infiltration of the solutions was regulated by the vacuum setting at which the fruits were equilibrated prior 1 This study was supported in part by Hatch Funds. to infiltration (Fig. 1). Fruits were infiltrated at 5 ml/ lOOg tissue. Solutions used were 0.01, 0.1, and 1.0 mm of IAA or 2,4-D in combination with 0.3 M mannitol as a carrier solution (10). The resulting auxin concentration in the fruit tissue was one-twentieth of the auxin concentration in the infiltration solution. After infiltration the fruits were kept at room temperature, and samples were taken at intervals for measure-

Low temperature and oxygen stresses were imposed during the first 48 hr of germination on 2 lines of snap bean (Phaseolus vulgaris L.), stress tolerant (PI-165426-BS) and stress-sensitive (‘Goldcrop’). At 22°C, O2 concentrations of 0%, 1%, and 2% increased leakage from the seeds, delayed emergence, and reduced growth, compared to 5% and 21% O2. These effects were aggravated by reducing the initial seed moisture from 12% to 8% in ‘Goldcrop’, but not in PI-165426-BS. At 10°, the effect of oxygen deficiency was minimized. Low temperatures inhibited growth of ‘Goldcrop’, but not of PI-165426-BS, and increased leakage from seeds of both lines. The survival of seeds exposed to the low temperature decreased when initial seed moisture was reduced from 12% to 8%. Flooding the seeds for 24 hr increased leakage and reduced emergence and growth much more than 24 hr of complete anoxia. Since the effects of anoxia are different than flooding injury, a mechanism of flooding injury not related to oxygen deficiency is discussed.