NON-NUTRITIONAL STRESS ACCLIMATION OF MYCORRHIZAL WOODY-PLANTS EXPOSED TO DROUGHT

Mycorrhizal enhancement of drought resistance of two woody plant speci es, loblolly pine (Pinus taeda L.) and rose (Rosa hybrida L. cv. Ferdy ), occurred independently of phosphorus nutrition. Mycorrhizae tended to alter root morphology and carbon allocation patterns of shoots and roots. Increased drought resistance of mycorrhizal plants was in part attributed to drought-induced colonization by mycorrhizae and the abil ity of the mycorrhizal plants to maintain high transpiration rates as a result of greater lateral root formation and lower shoot mass (in ec tomycorrhizal loblolly pine), and a higher root/shoot ratio and leaf a bscission (in endomycorrhizal roses). Neither the endo- nor ectomycorr hizal symbionts affected osmotic adjustment of droughted plants.