Abstract: | Leaf diffusion resistance interpreted as stomatal resistance,leaf water potential (w), solute potential (s) and leaf turgorpotential (p) of the chilling sensitive species Phaseolus vulgariswere determined during chilling at 4 °C in the light. Bothchill-hardened and non-hardened plants were used. For comparison,the chilling resistant species Pisum sativum was also used. The results for chilled P. sativum were similar to those obtainedfor chill-hardened P. vulgaris plants receiving a chilling treatment.In both cases a reduction in stomatal aperture and the maintenanceof a positive leaf turgor were the responses to chilling. Leavesof chilled but non-hardened P. vulgaris plants were found tomaintain open stomata throughout the chilling treatment despitea severe wilt developing after 7 h at 4 °C. This was incontrast to the chill-resistant P. sativum. which showed a rapidclosing and subsequent re-opening of the stomata to a new reducedaperture. During the first 12 h of chilling wof P. vulgaris leaves changedfrom 0.47 MPa to 1.24 MPa. On more prolonged chillingw tended to return to pre-chilling values. In addition. p decreasedfrom 0.42 MPa to zero after only 9 h of chilling, and remainedat this value for the remainder of the chilling period, s, changedrapidly from 0.89 MPa to 1.35 MPa in the first7.5 h, and after 9 h. w and s, were equal, i.e. zero p. In contrast,the chilling resistant plant P. sativum maintained a positivep throughout the chilling period, and there was little differencebetween values of w, and s in control and chilled leaves. Key words: Chilling, Stomata, ater relations, Phaseolus vulgaris, Pisum sativum |