Effect of Nitrogen Nutrition Upon Sugar Content and Dry Weight of Juvenile Lodgepole Pine and White Spruce

Abstract

A factorial experiment was conducted in which Pinuscontorta var. latifolia and Piceaglauca (Moench) Voss seedlings were grown for 6 weeks under controlled environmental conditions with deficient and normal supplies of nitrate and ammonium. Free sugars (sucrose, fructose and glucose), starch (as glucose) and pectic sugars (galactose, arabinose, mannose and xylose) were quantitated. Effects of nitrogen form and nitrogen level, and their interactions, upon sugar contents and dry weights of the two species were examined. Growth responses to nitrogen occurred mainly in the shoots. For most parameters the two species reacted similarly to changes in nitrogen level and form, although the concentration of individual sugars differed between the species. In the shoots there were level × species interactions in the dry weight and the sum of free sugars plus starch. Plants grown under nitrogen deficiency were characterized by higher starch contents throughout and lower free sugars in the shoots. Supplying nitrate instead of ammonium lowered glucose levels, particularly in the shoots. Pectic sugar contents were unaffected by nitrogen nutrition. These compositional and growth responses to the nutritional regime implied changes in carbohydrate metabolism and physiological processes that are described by the C/N ratio of the plant.