Abstract
In order to study effective methods for nondestructive analysis of water-stressed leaves, changes in spectral reflectance, stomatal conductance, PS‡U Yield (ΦPSII), and shape of cucumber leaves during dehydration were measured. Dehydration was induced by ceasing the regular watering of potted plants. The relationships between these changes and indexes of water stress, such as water potential, pressure potential, osmotic potential, water content per dry matter (WC), water saturation deficit (WSD), and water content per leaf area (LWC), were then examined. Leaves with water potential above about -1.5MPa recovered after re-watering but those with water potential below -1.5MPa did not recover and died. For water potential above -0.8MPa, changes in stomatal conductance and shape relating to wilting were principally caused by changes in pressure potential. Changes in ΦPSII depended on changes in osmotic potential for water potential below -0.5MPa. The ratio of reflectance at 1,450nm to reflectance at 850nm showed a good linear correlation (R2=0.91) over a wide range of water potentials above -7.1MPa. However, only slight changes occurred in the ratio of spectral reflectance of recoverable leaves with water potential above -1.2MPa.
