GROWTH AND WATER RELATIONS OF KENTUCKY COFFEE TREE IN PROTECTIVE SHELTERS DURING ESTABLISHMENT

Growth and water relations of Kentucky coffee tree [Gymnocladus dioica (L.) K. Koch] whips in translucent tubelike shelters were investigate d. In a container study, 1.2-m-high shelters were placed over whips fo llowing transplanting, then diurnal microclimate, water relations, and water use were measured. Shelter air temperature and vapor pressure w ere substantially higher, and solar radiation was 70% lower, than ambi ent conditions. Sheltered trees responded with nearly three-times high er stomatal conductance than nonsheltered trees. However, due to subst antially lower boundary layer conductance created by the shelter, norm alized water use was 40% lower. In a second experiment, same-sized she lters were placed on whips following spring transplanting in the field . Predawn and midday leaf water potentials and midday stomatal conduct ance (g(s)) were monitored periodically through the season, and growth was measured in late summer. Midday g(s) was also much higher in fiel d-grown trees with shelters than in those without. Sheltered trees in the field had four times greater terminal shoot elongation but 40% les s stem diameter growth. Attenuated radiation in the shelters and lower specific leaf area of sheltered trees indicated shade acclimation. Sh elters can improve height and reduce water loss during establishment i n a field nursery, but they do not allow for sufficient trunk growth.