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The recent visualization of stomatal nanoparticle uptake ended a 40-yr-old paradigm. Assuming clean, hydrophobic leaf surfaces, the paradigm considered stomatal liquid water transport to be impossible as a result of water surface tension. However, real leaves are not clean, and deposited aerosols may change hydrophobicity and water surface tension., Droplets containing Na Cl, Na Cl O3, ( NH4)2 SO4, glyphosate, an organosilicone surfactant or various combinations thereof were evaporated on stomatous abaxial and astomatous adaxial surfaces of apple ( Malus domestica) leaves. The effects on photosynthesis, necrosis and biomass were determined. Observed using an environmental scanning electron microscope, Na Cl and Na Cl O3 crystals on hydrophobic tomato ( Solanum lycopersicum) cuticles underwent several humidity cycles, causing repeated deliquescence and efflorescence of the salts., All physiological parameters were more strongly affected by abaxial than adaxial treatments. Spatial expansion and dendritic crystallization of the salts occurred and cuticular hydrophobicity was decreased more rapidly by Na Cl O3 than Na Cl., The results confirmed the stomatal uptake of aqueous solutions. Humidity fluctuations promote the spatial expansion of salts into the stomata. The ion-specific effects point to the Hofmeister series: chaotropic ions reduce surface tension, probably contributing to the defoliant action of Na Cl O3, whereas the salt spray tolerance of coastal plants is probably linked to the kosmotropic nature of chloride ions. [ABSTRACT FROM AUTHOR]

Broccoli (Brassica oleracea L. var. capitata L.) leaf waxes were labelled with [2-14C]acetate and examined during synthesis and deposition using microautoradiography. Waxes were viewed with light microscopy and scanning electron microscopy (SEM), including cryo-SEM. In microautoradiography, silver grains resulting from radioactive decay of labelled waxes seemed to be distributed randomly throughout the cuticle. This random distribution supports the hypothesis of diffusion or complex anastomosing pores as the mechanism of epicuticular wax deposition. The hypothesis of wax-depositing pores running perpendicular to the leaf surface is not supported. [ABSTRACT FROM AUTHOR]

Low activities of the monomeric aluminium (Al) species, Al3+, Al(OH)22+ and Al(OH)2+ in solution reduce root growth and root hair development in soybean [Glycine max (L.) Merr.]. Calcium (Ca) ameliorates to a certain extent the toxic effects of Al on root growth, but the interactive effects of Ca and Al on root hair development are not known. In the absence of added Al in solution culture, Ca concentration over the range 500-2000 μM had little effect on root growth or root hair development of soybean cv. Fitzroy. Where the sum of the activities of the monomeric Al species was 2 μM, taproot elongation and lateral root development of soybean was suppressed in solution with 500μM Ca. The length of the root hair zone was only 10% of that in plants not exposed to Al, and scanning electron microscopy revealed a low density of root hairs. Increasing the Ca concentration to 2000 μM largely overcame these deleterious effects. The results are discussed in relation to the role of root hairs as infection sites for Bradyrhizobium, and the known effects of Al in suppressing nodulation in soybean. [ABSTRACT FROM AUTHOR]

Scanning electron microscopy was used to investigate the effects of O3 fumigation (70 d of 240 μg O3 m-3 for 6 h d-1, during a 12 h photoperiod) on the condition of the epicuticular wax that fills and surrounds the stomatal antechamber of the needles of seven clones of Norway spruce (Picea abies (L.) Karst.). The rate of change of the physical structure of the wax differed between clones, but in all cases O3 accelerated the process on current and previous year's needles. The change consisted of a transition from a crystalline array of fine tubes to an amorphous, 'melted' layer with no visible structure. This resulted in a higher frequency of stomata occluded by an apparently continuous plug. In four clones, O3 fumigation resulted in 70 - 80% of the stomata on previous year's needles being occluded, in contrast to 7- 28% in charcoal-filtered air. Five of the clones showed a greater effect of O3 on the wax of the previous year's needles than on current needles. The physiological consequences of such O3-induced effects are discussed. Premature wax degradation induced by O3 and/or acid mist may have contributed to the decline of spruce in high-altitude forests of continental Europe. [ABSTRACT FROM AUTHOR]

Scanning electron microscope examination of the morphology of adaxial and abaxial leaf surfaces of salt spray-tolerant and normal plants of Agrostis stolonifera L., Dactylis glomerata L. and Holcus lanatus L. was carried out. Differences were found in degree and types of waxiness of epidermal cells, number and size of macro-hairs and prickles, epidermal cell lengths and extent to which stomata were sunken. These differences were consistent with a reduction of the wettability, and hence salt spray damage, to adaxial leaf surfaces. Abaxial leaf surface differences were much less pronounced. [ABSTRACT FROM AUTHOR]

A wick feed method was used to recrystallize a range of different plant epicuticular waxes from solutions in organic solvents. Using the scanning electron microscope the ultrastructure of the recrystallized wax from each species was compared with that of the wax on the corresponding intact plant surface and in many cases was found to be similar. It is concluded that the crystal structure of epicuticular waxes is greatly influenced by their inherent chemical and physical properties rather than by properties of the underlying curricular membrane or by any mechanism of extrusion or transport of the wax to the plant surface. [ABSTRACT FROM AUTHOR]

This article informs that thirteen fossil Erica-type seeds extracted by D.G. Wilson from samples collected from the Cromer Forest Bed Series at Pakefield, Suffolk, and Beeston, Norfolk, were examined in the Cambridge Stereoscan Mark II scanning electron microscope at the New University of Ulster. Of the thirteen fossil seeds examined under S.E.M. five were assigned with varying degree of certainty to Erica lusitanica. They could be distinguished from Bruckenthalia spiculifolia on the basis of the characteristics already noted. One seed was tentatively identified with Erica tetralix L., though poor preservation made confirmation impossible. All but one of the remainder were too poorly preserved to permit confident identification.

Unpollinated, cross-pollinated and self-pollinated stigmas of Brussels sprouts and kale were examined in a scanning electron microscope as fresh uncoated specimens. The stigmatic papillae are closely appressed in young stigmas, but are held apart in the mature stigma by the swollen bases of the papilla cells. Some self-pollen tubes show obvious signs of inhibition by being very short, or by coiling over the surface of the papilla without penetrating it. Other self-pollen tubes appear to behave like cross-pollen tubes by producing tubes which penetrate papillae directly. The implications of these observations for the identification of the site of the incompatibility reaction are discussed. [ABSTRACT FROM AUTHOR]

The morphology of the inner and outer surfaces of cuticular membranes of mono- and dicotyledonous leaves and fruits was studied with the scanning electron microscope. Variations in surface structure are related to differences in thickness and composition of the membranes. Delicate leaf membranes have fine ridges and simple stomata, well-developed membranes, thick V-shaped ridges and heavily cutinized stomata. Fruit membranes show deep ridges and extensive secondary cutinization. The most heavily cutinized structures occur in membranes which yield high proportions of 10, 16-dihydroxyhexadecanoic or 9,10,18-trihydroxyoctadecanoic acid which suggests that the membrane thickness and the complexity of the structural features are associated with the degree of hydroxylation of the constituent cutin acids. The relationship between the structure and composition of the cuticular membrane and the type and growth habit of the plant is discussed. [ABSTRACT FROM AUTHOR]