Influence of Epicuticular Waxes on Foliar Absorption of Nitrate Ions by Apricot Leaf Disks

Abstract

The poor response of Prunus spp. to foliar nitrate sprays under field conditions (Leece and Kenworthy 1971) is not caused by an inability of Prunusleaves to metabolize nitrate ions (Leece, Dilley, and Kenworthy 1972). This is analogous to the response ofPrunus spp. to urea sprays (Dilley and Walker 1961a). Dilley and Walker (1961b) demonstrated that pretreatment of peach leaf disks by immersion in acetone to dissolve lipid components of the cuticle increased subsequent urea absorption. Bukovac (1965) found that lightly brushing the upper and lower surfaces of peach leaves with a camel-hair brush enhanced uptake of 3-chlorophenoxy-a-propionic acid by 22 and 34% respectively. Brushing was assumed to have partially removed or rearranged the epicuticular waxes.This paper reports that the uptake of nitrate ions by apricot leaf disks, via the astomatous cuticle, was enhanced by partial removal or disruption of the epicuticular waxes. Materials and MethodsFully expanded, mid-shoot leaves were obtained from 5-year-old apricot trees (Prunus armeniaca L. cv. Curtis) growing at East Lansing during the summer of 1970. The leaves were transferred to the laboratory in polyethylene bags at 0-4°C.Nitrate ion uptake by apricot leaves was assayed by measuring the induction of nitrate reductase in excised leaf disks, following cuticular penetration. Apricot leaf disks were prepared for the uptake studies using the technique of Sargent and Blackman (1962) as modified by Greene and Bukovac (1971). Glass cylinders (height 10 mm; external diameter 24 mm; internal diameter 21 mm) were attached to the upper, astomatous surface of leaf disks (diameter 25 mm) using RTV Illiquid silicone rubber (General Electric Company, Waterford, New York) hardened with Harter T I catalyst (Wacher Chemie GMBH Company, Munich, Germany)_ The disks were placed in 9-cm Petri dishes lined with moist filter paper, and 1·0 ml ofO'4M KCl (control) or 0·4M KNOa (enzyme induction solution) was pipetted into each cylinder. Both solutions contained 0·1 % (v/v) X 77 surfactant (alkylarylpolyoxyethylene glycols, free fatty acids, and isopropanolChevron Chemical Company, Ortho Division, San Francisco, California). The dishes were incubated in a water-bath at 25°C for 15 hr and at a light intensity (from fluorescent tubes) of 8600 lux at leaf level. Following incubation, the glass cylinders were peeled off the disks, the disks were rinsed with distilled water, blotted dry, then assayed for nitrate reductase as previously reported (Leece, Dilley, and Kenworthy 1972).Where required, disruption and partial removal of epicuticular waxes was achieved either by brushing (10 strokes in one direction with a camel-hair brush), or with 80% (v/v) aqueous acetone (leaf wiped with acetone-treated tissue paper then dried immediately with untreated paper). Chloroform proved unsuitable for wax removal as it produced leaf senescence within 3 hr.

Response of ‘Burlat’ Sweet Cherry Trees to Postharvest Sprays of Nitrogen, Boron and Zinc

“…The above opinion can be confirmed in the studies of Eckert and Childers (1954) and Norton and Childers (1954) for peach (Prunus persica L.), Włodek et al (1959) and Leece and Dirou (1977) for prune (Prunus domestica L.), and Leece and Kenworthy (1972) for apricot (Prunus armeniaca). However, Hołubowicz (1974), Leece (1978), Swietlik and Słowik (1981), Rosecrance et al (1998), Tagliavini et al (1998), and Furuya and Umemiya (2002) were able to improve N status in nectarine (Prunus persica var nectarina), prune, peach, and sour cherry trees as a result of leaf-applied urea.…”

Salinity Damage to Norfolk Island Pines Caused by Surfactants. III. Evidence for Stomatal Penetration as the Pathway of Salt Entry to Leaves

“…Partial removal or disruption of the epicuticular waxes of apricot leaves was shown to double the uptake of nitrate ions through the astomatous cuticle (Leece and Kenworthy 1972). Such damage produced by surfactants was considered as a possible cause of NaCl uptake from sea-spray but electron microscopy of the cuticle showed no evidence of damage despite observed changes in the waxy fibrils over the stomata after repeated applications of solution.…”

Quantitative and Qualitative Characterization of Carrot Root Periderm during Development

“…Carrots have been reported to lose approximately half of their high-boiling volatile terpenoids upon canning (3) and 15% to 20% of their carotenoids (1 ,7 , 16). In addition, cultivar differences have been noted for canned snap bean flavor volatiles (15) and processed carrot firmness (4,8).…”

“…The structure, location, and chemistry of the cuticle limits water loss and provides a barrier to the uptake of foliar-applied chemicals (15,18). In addition, the cuticle serves as a protective barrier to insect and disease infestation (17).…”