Pressure-volume analysis of tissue water relations parameters for individual fascicles of loblolly pine (Pinus taeda...

A technique was tested for obtaining water relations parameters from individual fascicles of loblolly pine needles by the pressure-volume curve method. Comparisons were made between parameters derived from (1) individual fascicles that were rehydrated in a pressure chamber after being removed from the shoot and (2) fascicles that were rehydrated on the shoot. Estimates of tissue osmotic potential for needles rehydrated by the two methods were significantly different for needles from terminal shoots, but not significantly different for needles from lateral shoots. Similarly, a significant difference in the estimated tissue elasticity at zero water potential was noted for needles on terminal shoots, but not for those on lateral shoots. It is suggested that differences due to rehydration method are related to the duration of the rehydration period and not the choice of technique. The use of fascicles of needles, rehydrated after detachment, allows repeated estimation of the tissue water relations of a single conifer shoot.