The growth of some New Zealand trees

Abstract

Summary Growth of Acer pseudoplatanus was compared with the New Zealand species Fuchsia excorticata. Aristotelia serrata, and Hoheria glabrata (deciduous) and Nothofagus menziesii, N. fusca, and N. solandri (evergreen) under long, short, and natural days in a greenhouse and outdoors. Acer rapidly became dormant in short days, as has been reported from the Northern Hemisphere. The New Zealand species, however, continued growth through the summer in all day lengths, and stopped only when temperatures began to decline with the approach of winter. Then all species became dormant, most rapidly in natural day lengths with the plants in short days usually soon following. In Hoheria and Fuchsia, however, dormancy was delayed in short days. In all species it was delayed in long days. It thus appears that the shortening days of autumn are involved in producing the natural dormancy of New Zealand trees, but are effective only in conjunction with declining temperature. In Northern Hemisphere trees, by contrast, it is known that short days fail to bring on dormancy at low temperatures and that low temperatures break dormancy already induced The temperature at which short days became effective for the New Zealand trees was not, however, as low as is needed to break dormancy in Northern trees, for Acer did not come into leaf after wintering in the greenhouse in which the New Zealand trees ceased growth in the winter and came into leaf quite normally the following spring. It thus appears that the winter quiescence of New Zealand trees is different from the dormancy induced by short days in Acer. Internode length was not affected by day length in Aristotelia. but in the rest, including Acer, it was less in short days. All species had shorter internodes outdoors than in the greenhouse. Leaf fall followed dormancy in response to short days in Acer. The native species lost leaves sporadically through the year in controlled day lengths 11 in nature, but the autumn peak periods were earlier out-of-doors than in the greenhouse, indicating an effect of temperature.