The growth conditions involved both low-temperature treatment and the addition of abscisic acid to the culture medium.

However, an 8-h photoperiod did enhance the effect of the low-temperature treatment at the young-seedling stage.

Similarly, there were stronger J–M correlations in the high- than in the low-temperature treatment.

A low-temperature treatment of 5:5°C increased the frost tolerance of cotyledon and young seedling stage germinants, while their response to a shortened photoperiod (8 h) was quite variable.

Frost cankers were induced by low-temperature treatments with freon in Pinus contoria var. latifolia, P. sylvestris, Malus sylvestris, Tilia cordata, Ulmus americana, and U. pumila.

Respiration rates in high-temperature treatments showed an initial increase to a wide peak (wider and later at 18 than at 26 °C), followed by a sharp decline; respiration of low-temperature treatments was nearly constant through time or declined slowly.