Anatomy and physiology of sugar maple (Acer saccharum March) seedlings uninoculated or inoculated with the vesicular-arbuscular endomycorrhizal fungus Glomus etunicatum

Abstract

Hanover, 1981).Webb (1976) investigated the effects of light intensity and photoperiod on root elongation rates and found that active root growth proceeded at the expense of shoot growth followed by a period of increased shoot growth and reduced root growth.The cyclic nature of these processes allowed for the maintenance of a relatively stable root to shoot ratio. Reduction in light intensity to a point that limited photosynthesis severely inhibited root growth, while a return to adequate light intensities resulted in normal rates of growth. It appeared that root growth was dependent on photosynthate supply. During a period of inactivity, roots became suberized. This was followed by the growth of white roots from these suberized tips during an active period. Taylor and Dumbroff (1975) and Dumbroff and Brown (1976) found that root growth in sugar maple continued through the winter ceasing only when the ground was frozen in December and January. A surge of root growth was observed in late February to early April indicating that this species prepares for spring growth very early in the year. In fact, sugar maple seeds are often observed to germinate under snow cover in early spring. An increase in cytokinin activity, just before bud break, followed this early root activity. It was suggested that synthesis of cytokinins is not the initial step leading to the breaking of shoot dormancy since cytokinin Bonfante-Fasolo, P., J. Dexheimer, S. Gianinazzi, V. Gianinazzi-Pearson, and S. Scannerini. 1981. Cytochemical modifications in the host-fungus interface during intracellular interactions in vesicular-arbuscular mycorrhizae. Plant Sci. Letters 22:13-21. Buwalda, J. G. and K. M. Goh. 1982. Host-fungus competition for carbon as a cause of growth depressions in vesiculararbuscular mycorrhizal ryegrass. Soil Biol. Biochem. 14:103-106.