FOLIAR ABSORPTION OF DEW INFLUENCES SHOOT WATER POTENTIAL AND ROOT-GROWTH IN PINUS-STROBUS SEEDLINGS

We investigated the effects of foliar absorption of dew by eastern whi te pine (Pinus strobus L.) seedlings on midday shoot water potential, as well as on other water relations variables and growth. Two-year-old container-grown eastern white pine seedlings were subjected to contra sting watering regimes (normal and deficient) and three frequencies of artificial dew (none, once and three times per week) for 10 weeks in a greenhouse. Midday shoot water potential was measured on four occasi ons during the study. Other water relations variables (relative water content, stomatal conductance, pressure-volume curves) and growth (hyp ocotyl diameter, aboveground dry mass, root dry mass) were also measur ed. Artificial dew significantly increased shoot water potential, stom atal conductance and seedling root growth, with greater responses obse rved for seedlings subjected to a deficient watering regime than for w ell-watered seedlings. Because dew can be a frequent microclimatic eve nt in some areas, this finding has practical implications for field st udies of water relations of eastern white pine and possibly of other c oniferous species.