A comparative study of shoot and root development of interior and coastal Douglas-fir seedlings

Abstract

Bud development and root elongation of coastal and interior seedlots of Douglas-fir (Pseudotsugamenziesii (Mirb.) Franco) were compared from September through March after 4 months of growth under Styroblock container nursery production conditions. Apical development of vegetative buds was described in terms of morphology, mitotic index, apical dimensions, and cell numbers. An estimate was made of the number of leaf primordia produced on the embryonic shoot. Morphological and anatomical stages of bud development in the interior variety occurred about 4 weeks in advance of those in the coastal variety. Cell divisions ceased in apices in November and December in interior and coastal varieties, respectively, and resumed in mid-February in both varieties, so all apices were undergoing cell division by March 1. Flushing was variable but occurred earlier in the interior variety. Numbers of white root tips were highest during October and March in both varieties. Root elongation tended to follow the pattern of bud development in each variety, so the interior variety had greater numbers of white root tips >0.5 mm long about 2 weeks earlier in the fall than the coastal variety. Apical activity and peak numbers of root tips >0.5 mm long were synchronized in both varieties by the following March. In the interior variety white root tips were absent during December and January whereas some were present throughout the sampling period in the coastal variety. The interior variety produced a larger bud and entered dormancy earlier than the coastal variety when cultivated under coastal conditions. Differences in phenology between the two varieties are sufficient to justify the development of more specific nursery cultural practices to achieve maximum seedling quality.