Cool storage of pine seedlings

Abstract

Aspects of the seedling physiology of Pinus radiata D. Don, and and Pinus mugo Turra, have been studied following periods in cool storage of up to 18 weeks. Prior to storage the seedlings were subject to different treatments of nurserybed wrenching and date of lifting.

Storage caused a marked reduction in the rate of photosynthesis, the level of carbohydrate resources and the capacity for translocation of ¹⁴C labelled assimilate. Pinus mugo, and to a lesser extent, wrenched seedlings of Pinus radiata, were able to recover in the absence of severe moisture stress after planting. Growth following all storage periods was not affected in the low stress climate of a controlled environment cabinet but was markedly reduced by field environment.

Wrenching did not reduce the effect of storage on the level of carbohydrate resources or on the capacity for assimilate translocation but did promote an earlier recovery of photosynthesis. As a result wrenching improved survival and growth in both species following storage.

Late, or spring lifting was more damaging to seedling vigour than the combination of winter lifting and cool storage, especially in Pinus radiata. The more resistant state of winter lifted seedlings was preserved in cool storage.

Pinus radiata could not adapt readily to cool storage as growth was dependent on current photosynthesis and this was critically reduced after 12 weeks storage. Maximum practical storage period in this species was 3-4 weeks.

Pinus mugo adapted readily to cool storage as this species is naturally dependent on stored carbohydrate resources for both winter survival and spring growth. Prolonged storage reduced the carbohydrate resource and limited growth, and under these circumstances current photosynthetic production was insufficient to sustain vigorous growth after planting. Maximum practical storage period was 18-20 weeks.

Both species gave the best survival and growth when planted out into a cool, moist environment.