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New Zealand Journal of Forestry (1969) 14(1): 50–58
©New Zealand Institute of Forestry

Research article
Water Relations of Wrenched and Unwrenched P. radiata Seedlings on Being Transplanted into Conditions of Water Stress

D.A. Rook

Internal water deficits and rates of transpiration of seedlings which had been unwrenched (C), root wrenched once (W/l), or wrenched at fortnightly intervals over the previous five months (W/F) were compared for seven days after being transplanted into conditions of water stress in a controlled environment cabinet. Relative turgidities of the needles of the seedling pretreatments were ranked in the order W/F > W/i > C. Rates of transpiration of the W/F seedlings were significantly higher than those of the seedlings of the other two treatments! Differences in rates of transpiration between detached shoots of the three treatments were slight; those of the W/F seedlings had the highest rates. Seven days after the seedlings were transplanted the root systems of only the W/F stock showed, many new roots. Results from this investigation support those from field trials which indicate that well-wrenched transplants survive dry conditions better than W/i plants, and even more so than C plants, owing in part at least to the effect of repeated wrenching in producing a root system more capable of meeting the requirements of the plant after transplanting.
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