Sa. Prior et al., INFLUENCE OF ATMOSPHERIC CO2 ENRICHMENT, SOIL N, AND WATER-STRESS ON NEEDLE SURFACE WAX FORMATION IN PINUS-PALUSTRIS (PINACEAE), American journal of botany, 84(8), 1997, pp. 1070-1077
Interactive effects of increasing atmospheric CO2 with resource limita
tions on production of surface wax in plants have not been studied. Pi
nus palustris seedlings were grown for 1 yr at two levels of soil N (4
0 or 400 kg N.ha(-1).yr(-1)) and water stress (-0.5 or -1.5 MPa xylem
pressure potential) in open-top field chambers under two levels of CO2
(365 or 720 mu mol/mol). Needle surface wax content was determined at
8 mo (fall) and 12 mo (spring) and epicuticular wax morphology was ex
amined using scanning electron microscopy (SEM) at 12 mo. Wax content
expressed on both a leaf area and dry mass basis was increased due to
main effects of low N and water stress. No main effects of CO2 were ob
served; however, a CO2 x N interaction at 12 mo indicated that under l
ow soil N the elevated CO2 treatment had less wax (surface area or dry
mass basis) compared to its ambient counterpart. Morphologically, low
N needle surfaces appeared rougher compared to those of high N needle
s due to more extensive wax ridges. Although the main effect of water
treatment on wax density was not reflected by changes in wax morpholog
y, the CO2 x N interaction was paralleled by alterations in wax appear
ance. Decreases in density and less prominent epicuticular wax ridges
resulting from growth under elevated CO2 and limiting N suggest that d
ynamics of plant/atmosphere and plant/pathogen interactions may be alt
ered.