Carbohydrate Status of Mycorrhizal and Nonmycorrhizal Citrus Rootstocks1

Abstract

Abstract Carbohydrates were analyzed in mycorrhizal and nonmycorrhizal citrus rootstock seedlings in greenhouse studies. Inoculated seedlings grew taller or weighed more and their leaves contained greater amounts of total soluble sugar, sucrose, reducing sugars, starch, and total nonstructural carbohydrate per gram of tissue than noninoculated controls, in a low P soil (9–12 ppm). Only the reducing sugars, fructose and glucose, increased slightly in roots of inoculated seedlings over those levels found in uninoculated control seedlings. Levels of reducing sugars were higher in leaves than in roots. Uninoculated seedlings grown in high P soil (210 ppm) were about the same height and their leaves contained levels of total soluble and reducing sugars similar to those in inoculated rootstocks grown in low P soil. It does not appear that these mycorrhizal fungi mobilize sugars as a sink for photosynthate in roots.