Winter variation in physiological status of cold stored and freshly lifted semi-evergreen Quercus nigra seedlings.

摘要

Water oak (Quercus nigra) is a tardily deciduous species commonly planted in afforestation projects in the Lower Mississippi River Alluvial Valley, USA. Field performance is often marked by low survival rates and top dieback, which may be associated with poor physiological quality of planting stock. We investigated physiological status of cold stored (2-4 degrees C; CS) and freshly lifted (FL) seedlings during the period between lifting and planting (December-February). In mid-February, seedlings were transplanted into a controlled greenhouse environment for 90 days to evaluate post-transplant growth performance. Net photosynthetic rates were positive until late January (generally greater in CS seedlings) and became negative thereafter. FL seedlings generally had lower LT₅₀ values from freeze-induced electrolyte leakage (FIEL), reflecting greater cold hardiness. FIEL of foliage provided the best indicator of physiological status, though terminal buds may serve as a suitable substitute. All seedlings experienced top dieback following transplant; CS seedlings had less relative root-collar diameter, height, and root volume increments. Cold storing seedlings did not appear to prolong dormancy, increase stress resistance, or hold promise as a means to improve outplanting success. Regardless of storage regime, seedlings appeared to be most cold hardy and perhaps stress resistant until late January.