Gas exchange and chlorophyll fluorescence responses of Pinus radiata D. Don seedlings during and after several storage regimes and their effects on post-planting survival

Abstract

Post-storage gas exchange parameters like CO2 assimilation, stomatal conductance, transpiration, water use efficiency and intercellular CO2 concentrations, together with several chlorophyll a fluorescence parameters: F o, F v, F v/F m, F m/F o and F v/F o were examined in radiata pine (Pinus radiata D. Don) seedlings that were stored for 1, 8 or 15 days at 4° or 10°C with or without soil around the roots. Results were analysed in relation to post-storage water potential and electrolyte leakage in order to forecast their vitality (root growth potential) following cold storage, and post-planting survival potential under optimal conditions. During storage at 4° and 10°C, photosynthesis was reduced, being more pronounced in bare-root seedlings than in seedlings with soil around the roots. The depletion of CO2 assimilation seemed not to be solely a stomatal effect as effects on chloroplasts contributed to this photosynthetic inhibition. Thus, the fall in the ratios F v/F m, F v/F o and F m/F o indicated photochemical apparatus damage during storage. Photosynthetic rate was positively correlated with the root growth index and new root length showing that new root growth is dependent primarily on current photosynthesis. Pre-planting exposure of bare-root radiata pine seedlings to temperatures of 10°C for more than 24 h during transportation or storage is not recommended.