The effect of inorganic nutrients on water economy and hardiness of conifers. : II. The effect of varying potassium and calcium contents on water status and drought hardiness of pot-grown Pinus silvestris L. and Picea abies (L.) Karst. seedlings
The effect of varying amounts of potassium and calcium on drought hardiness, transpiration rates, and water status of pot-grown seedlings of Pinus sivestris and Picea abies, 5 months old, was investigated. An increased potassium content increased the drought hardiness of pine seedlings but not of spruce. An increased calcium content decreased the drought hardiness of pine seedlings but had no effect on spruce. When the soil of the pots dried out both pine and spruce seedlings were killed at a xylem pressure potential of about -30 bars. Stomata1 closure began at a xylem pressure potential of about -10 bars and ended at -25 bars in both pine and spruce seedlings. Different potassium contents did not affect those values. The transpiration rate of potassium-deficient seedlings of pine and spruce was about 65per cent of that of normal- and high potassium seedlings. The positive correlation between potassium content of pine seedlings and survival at low water potentials could not be explained by low transpiration rate or early stomata1 closure as the water potential decreased. It \vas assumed that the potassium contents influenced the desiccation tolerance of the cytoplasm, through the colloidal properties or the metabolism of carbohydrates and proteins.
inorganic fertilizers; water economy; hardiness; conifers; Pinus silvestris; Picea abies; potassium; calcium
Studia Forestalia Suecica
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