V. Orbovic et al., Air temperature, humidity, and leaf age affect penetration of urea throughgrapefruit leaf cuticles, J AM S HORT, 126(1), 2001, pp. 44-50
Citations number
40
Categorie Soggetti
Plant Sciences
Journal title
JOURNAL OF THE AMERICAN SOCIETY FOR HORTICULTURAL SCIENCE
Effects of air temperature, relative humidity (RH), and leaf age on penetra
tion of urea through isolated leaf cuticles of 'Marsh' grapefruit (Citrus x
paradisi Macfad,) trees on 'Carrizo' citrange (C, sinensis L, Osbeck x Ponc
irus trifoliata (L,) Raf, rootstock were examined. Intact cuticles were obt
ained from adasial surfaces of 'Marsh' grapefruit leaves of various ages. A
finite dose diffusion system was used to follow movement of C-14-labeled u
rea from urea solution droplets across cuticles throughout a 4-day period.
Within the first 4 to 6 hours after urea application, the rate of urea pene
tration increased as temperature increased from 19 to 28 degreesC, but ther
e was no further increase at 38 degreesC. Increasing relative humidity incr
eased urea penetration at 28 degreesC and 38 degreesC, Cuticle thickness, c
uticle weight per area, and the contact angle of urea solution droplets inc
reased as leaves aged. Cuticular permeability to urea decreased as leaf age
increased from 3 to 7 weeks, but permeability increased in cuticles from l
eaves older than 9 weeks. Contact angles decreased with increased urea solu
tion concentration on leaf surfaces that were 6 to 7 weeks old, but solutio
n concentration had no effect on contact angle on cuticles from younger and
older leaves, Changing urea solution pll from 8.0 to 4.0 could have an eff
ect on the amount of urea penetrating the cuticle through the loss of urea
from breakdown possibly due to hydrolysis. Results from this study define l
eaf age, environmental conditions, and formulation for maximum uptake of fo
liar-applied urea.