The influence of photoperiod and temperature on the development of frost hardiness in seedlings of pinus silvestris and picea abies
Physiologia Plantarum 44(3): 288-294
ISSN/ISBN: 0031-9317 DOI: 10.1111/j.1399-3054.1978.tb08634.x
The influence of short days and low temperature on the development of frost hardiness in seedlings of Scots pine (P. silvestris L.) and Norway spruce [P. abies (L.) Karst.], grown for 6 mo. in glasshouses and climate chambers, was investigated. The degree of hardiness was estimated by freezing the shoots of the seedlings to predetermined temperatures. After 8 wk in a glasshouse the viability of the seedlings was determined by establishing bud flushing. The most effective climate for the development of frost hardiness was short days (SD) and low temperature (2.degree. C); the next most effective was SD and room temperature (20.degree. C). Long days (LD) and low temperature also had a marked effect on the development of hardiness. A combination of 3 wk treatment with SD and 20.degree. C, and 3 wk with SD and 2.degree. C gave the same results as 6 wk with SD and 2.degree. C. The results clearly demonstrate the importance of the photoperiod prior to low temperature for the development of frost hardiness. Both short days and low temperature induce frost hardiness development. Probably this occurs by initiation of different processes in the 2 cases. The degree of frost hardiness development appears to depend on the sum of these different processes and on the timing between them.