RESUMO
Mycorrhizal enhancement of drought resistance of two woody plant species, 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 ability of the mycorrhizal plants to maintain high transpiration rates as a result of greater lateral root formation and lower shoot mass (in ectomycorrhizal loblolly pine), and a higher root/shoot ratio and leaf abscission (in endomycorrhizal roses). Neither the endo- nor ectomycorrhizal symbionts affected osmotic adjustment of droughted plants.
RESUMO
A nondestructive technique for repeatedly estimating total surface area of water-stressed pine (Pinus taeda L.) fascicle segments was evaluated. Fascicle radius was measured with a digital caliper and needle surface area calculated on the assumption that the needles were segments of a cylinder. High correlations (r >/= 0.94) were found between surface area estimated in this way and surface area calculated (a) from needle displacement, also on the assumption that needles are segments of a cylinder, and (b) from needle dry weight using a regression between dry weight and surface area estimated from needle displacement. The caliper-radius method gave slightly lower estimates of surface area than the other methods. However, differences among surface area estimates made with the three methods and between estimates made on water-stressed and fully hydrated needles were small relative to variances of leaf gas exchange measurements.
