Epicuticular Wax Deposition Research Articles

The impact of epicuticular wax on gas-exchange and photoinhibition in Leucadendron lanigerum (Proteaceae)

This study investigated the seasonal modification of wax deposition, and the impact of epicuticular wax on gas-exchange as well as photoinhibition in Leucadendron lanigerum , a species from the Proteaceae family with wax-covered leaf surfaces and the stomata also partially occluded by wax. The results of this study demonstrated that the deposition of epicuticular wax in L. lanigerum is dependent on the age of the leaf as well as the season, and generation and regeneration of wax occur mostly in spring while transformation and also degeneration of wax crystals occur in winter. Epicuticular waxes decreased cuticular water loss, but had little impact on leaf reflectance. The temperature of leaves without wax was lower than that of wax-covered leaves, indicating that the rate of transpiration impacted more on leaf temperature than reflectance of light in the PAR range in L. lanigerum . The wax coverage at the entrance of stomata in L. lanigerum increased resistance to gas diffusion and as a consequence decreased stomatal conductance, transpiration and photosynthesis. Also, the results indicated that epicuticular waxes do help prevent photodamage in L. lanigerum , and so this property could benefit plants living in arid environments with high solar radiation.

Effect of environment on giant foxtail (Setaria faberi) leaf wax and fluazifop-P absorption

Controlled-environment experiments were conducted to determine giant foxtail epicuticular wax (ECW) deposition and fluazifop-P absorption under different environmental conditions and with two adjuvants. Drought stress and low temperature increased leaf ECW content, whereas low light intensity decreased ECW content compared with medium light intensity. Drought stress conditions decreased the fatty acid and primary alcohol content of ECW and increased the hydrocarbon content compared with field capacity. Compositional changes would make the ECW more hydrophobic and reduce leaf wetting by herbicide spray. Increasing air temperature decreased the aldehyde content of ECW, whereas decreasing light intensity increased ECW fatty acid and aldehyde content while decreasing primary alcohols and esters. Compositional changes under low light intensity would make the ECW more hydrophilic and increase leaf wetting by a herbicide spray. Drought stress reduced fluazifop-P absorption regardless of the temperature but could not further reduce fluazifop-P absorption under low light intensity. Fluazifop-P absorption by plants under low light and drought stress conditions was similar to plants under low or medium light intensity and field capacity conditions. Similarly, the rate of fluazifop-P absorption was less under drought stress and low light conditions. Fluazifop-P absorption was greater when crop oil concentrate was added compared with 28% urea ammonium nitrate or no additive. Crop oil concentrate, added to the herbicide solution, overcame reduced fluazifop-P absorption under the low light conditions and in one of the two drought stress regimes but could not overcome reduced fluazifop-P absorption with the high temperature regime.

Adaptative anatomical characteristics of grapevine leaf in the south of Tunisia

<p style="text-align: justify;">The adaptation qualities of local (Razegui, Asli) and introduced (Cardinal) grapevine cultivars were evaluated through an experimental test carried out in the Tunisian Sahara (Rjim-Mâatoug), characterized by severe environmental conditions (temperature, light intensity, sirocco and salinity). These adaptation qualities were evaluated on an anatomical and ultrastructural scale.</p><p style="text-align: justify;">Thus, the histological study showed a significant difference in vine leaf blade thickeness between the north and the south, in Cardinal cultivar. The Scanning Electron Microscope results showed a remarkable difference in the leaf epidermic cell shapes between the north and the south-cultivated varieties. We think that this difference is due to abundant epicuticular wax deposits observed as irregular crystalloid plates which are definitely more abundant in the northern leaf samples than in the southern. In parallele, the transverse leaf blade section showed thicker « cuticle and outer epidermal cell wall » in the southern leaf samples than in the northern. Besides, the transmission microscopy observations confirmed the thickening of the abaxial epidermis surface, which is mainly attributed to the cell wall simultaneously with a wax accumulation across the cuticule, in the Sahara.</p>

Anatomia foliar de quatro espécies do gênero Cattleya Lindl. (Orchidaceae) do Planalto Central Brasileiro

As espécies analisadas (Cattleya araguaiensis Pabst, C. bicolor Lindl., C. nobilior Rchb. e C. walkeriana Gardn.) apresentam epiderme uniestratificada em ambas as faces da lâmina foliar, ocorrendo estômatos na face abaxial; deposição de cera epicuticular em crostas, escamas, flocos e plaquetas; em C. araguaiensis ocorrem estegmatas incrustados nas células epidérmicas; em todas as espécies ocorre hipoderme com células de paredes espessadas; mesofilo bifacial, compacto; células paliçádicas atípicas, com barras de espessamento; feixes vasculares colaterais dispostos alternadamente, acompanhados por bainha de fibras; cordões fibrosos acompanhados por estegmatas ocorrem longitudinalmente na lâmina foliar; presença de ráfides. Os aspectos descritos revelam acentuada xeromorfia, em função de economia de água.

Effects of elevated [CO2] and O3 on stomatal and surface wax characteristics in leaves of pubescent birch grown under field conditions

The responses of pubescent birch (Betula pubescens Ehrh.) leaves to elevated levels of carbon dioxide and ozone were investigated. The micropropagated birch clones used in this research were divided into coastal (Kempele 64°N °25E) and inland (Ylikiiminki 65° N 26°E) clones according to the provenance of the parent tree. The seedlings were exposed to elevated levels of CO2 and CO2+O3 in open-top chambers over four growing seasons (1993–1996). The leaves used in this investigation were gathered in 1995 and 1996. Leaf characteristics seemed to be dependent on leaf age and weather conditions. Stomatal density was greater in plants grown in open-top chambers relative to unchambered controls. The CO2 and CO2+O3 treatments did not affect the stomatal density of the birches. However, the mean stomatal size of the coastal clone increased significantly (13%) in the CO2 treatment compared with the filtered and ambient controls in 1995. In 1996, the mean stomatal sizes of the inland clones were also significantly higher in the CO2 (10%), CO2+O3 (11%) and non-filtered (12%) treatments compared with the filtered control. The distribution of wax deposits on the abaxial leaf surface increased in the inland clone under elevated levels of CO2. The growth environment affected the development of the epicuticular waxes: non-filtered air, CO2 and CO2+O3 treatments seemed to stimulate the formation of wax deposits compared with the charcoal filtered control in which wax formation was the weakest. The combined effects of elevated CO2 and O3 levels on the stomatal size and epicuticular wax deposits were similar in comparison to the effects of elevated CO2 levels alone.

Effect of different salts and of ABA on growth and mineral uptake in Jojoba shoots grown in vitro

ABA and different kinds of salinity were compared for their effect on shoot development in salt-sensitive and salt-tolerant jojoba clones. Shoot segments were proliferated in vitro in the presence of different salts or different concentrations of ABA. Growth parameters (shoot elongation, new node production, dry weight, leaf length) and accumulation of Na+, K+, Ca2+, Cl−, and SO42- were examined. Wax deposition on leaves was detected by electron scan microscopy. Chloride salinity reduced shoot elongation, node production, and biomass production in salt-sensitive clones, while in salt-tolerant clones its adverse effects were generally less pronounced (although significant inhibition was observed in the presence of Na2SO4) or it even enhanced growth. The effect of ABA on shoot growth was similar to that of the chloride salinities, with salt-sensitive clones responding to much lower ABA concentrations than the salt-tolerant ones. Unlike ABA, salinity (mainly salts containing Cl− anions) significantly promoted leaf expansion in both sensitive and tolerant clones. ABA and salinity induced some epicuticular wax deposition on leaves of salt-sensitive clones. The conclusion is that the salt sensitivity of jojoba clones is partly related to sensitivity to ABA.

How in vitro light affects growth and survival of ex vitro cassava

SummaryCassava is one of the most important food crops in Africa. Meristem culture is an effective method of eliminating viruses and other systemic diseases spread through the vegetative propagation of stems. However, in semi‐arid conditions, survival of ex vitro plants in the field is often disappointing. When an increasing range of light regimes in vitro was provided, the fresh and dry masses more than doubled their values between 29 and 369 mmol s−1 m−2 PPFDs. Increases in numbers of senescent leaves and stem thickness were also recorded with increasing PPFD. However, PPFD above 101 mmol s−1 m−2 resulted in 30–70% reduction in plant survival, with the thin plants with the smallest fresh and dry masses being the ones with highest survival rates. High light and temperature levels in the greenhouse were also found to be critical for plant survival. It was also shown that transpirational loss from detached leaves and epicuticular wax deposits were not good indicators for predicting survival of ex vitro cassava plantlets during acclimatisation.

QUALITY BIOMASS PRODUCTION VIA PHOTOAUTOTROPHIC MICROPROPAGATION

The commercial use of conventionally micropropagated plantlets is often undermined by their poor physiological quality and growth. A substantial percentage of plantlets cannot survive or cannot grow fast and vigorously after transplantation in the ex vitro conditions. This limits the possible prospects of this unique propagation technique. Plantlets grown under conventional micropropagation system (with use of 20 - 30 g l -1 sucrose in the medium and airtight vessels) are often characterized by non-functional stomata and limited epicuticular wax deposition on the leaves. Thus, immediately after transplantation, rapid water loss due to uncontrolled transpiration occurs followed by wilting. These effects are probably due to the prolonged exposure of the plantlets to high relative humidity in vitro (> 95 %) and low CO 2 concentration and photosynthetic photon flux in the culture vessels during the photoperiod. The presence of sucrose in the medium and the accumulation of ethylene in the vessel may also play a role. The photoautotrophic micropropagation system (without any sucrose in the nutrient medium and with enriched CO 2 and high photosynthetic photon flux), especially under forced ventilation, has been proved to produce morphologically superior and physiologically normal quality transplants. Plantlets grown in vitro under photoautotrophic conditions show high net photosynthetic rate, enhanced shoot and root growth and shortened multiplication period and the leaves contain functional stomata and high wax content. These plantlets exhibit less water loss after transplantation, as a result leaves do not wilt and grow fast even without any special ex vitro acclimatization. In photoautotrophic micropropagation, humidity is controlled (< 90 %) and the CO 2 concentration is raised and ethylene can not accumulate simply due to increased air exchange rate of the culture vessel. Our recent research on the scaled-up vessel with forced ventilation system and on the aseptic culture room as an alternative for many large culture vessels for photoautotrophic micropropagatior. is introduced in this article.

Effects of Elevated Atmospheric CO2 Concentration on Leaf Anatomy and Morphology in Panicum Species Representing Different Photosynthetic Modes.

Panicum tricanthum Nees, Panicum antidotale Retz., and Panicum decipiens Nees ex Trin. were selected to represent C3, C4, and C3/C4 intermediate perennial species of Panicum, respectively. Plants grown from seed with 900 ppm [CO2] under natural sunlight and controlled temperatures (30 degrees /22 degrees C) were compared with plants grown with ambient [CO2]. The anatomy of the last fully expanded leaf of the main tiller was studied by light microscopy with computerized graphic image analysis and by transmission electron microscopy. Leaf anatomy did not change qualitatively in response to elevated [CO2], but there were changes in leaf thickness and in the proportions of total transsectional area occupied by mesophyll, bundle sheath cells, vascular elements, and sclerenchyma, according to species. The abaxial stomatal frequency decreased by 22% for P. tricanthum but increased by ca. 30% for the other two species. With 900 ppm CO2, all three species showed a considerable increase in leaf starch content (to >30% of dry matter). Starch granules accumulated in chloroplasts of the mesophyll and bundle sheath cells. Increased leaf glaucousness in response to elevated [CO2] was the result of increased or modified deposition of epicuticular wax on both leaf surfaces, a response to elevated [CO2] that is unusual and one that has not been previously recorded for monocotyledons. The wax patterns were studied by scanning electron microscopy. Panicum decipiens did not respond to elevated [CO2] in a truly intermediate fashion; its responses resembled those of either the C3 or the C4 species. C3/C4 intermediates may thus be interpreted as developmental chimeras and not as species in transition between C3 and C4 modes in an evolutionary sense.

PHYSIOLOGICAL ASPECTS OF IN VITRO-GROWN COCONUT (Cocos nucifera L.) PLANTS DURING ACCLIMATIZATION

The physiological status of in vitro-grown coconut (Cocos nucifera L.) plants during acclimatization was studied using nursery-raised seedlings as the control. The percentage of open stomata in leaves of in vitro-grown coconut plants was high at the initial stage of acclimatization but decreased during the course of acclimatization indicating an improvement in stomatal regulation. A progressive increase in the stomatal density, epicuticular wax deposition and leaf thickness in in vitro-grown plants was observed during acclimatization. As a result of the low light intensity, the epidermal cells of in vitro-grown plants were narrower and longer when compared to the control. With the exposure of plants to increased light intensity, the cells became wider and shorter as observed in the control.&#x0D; &#x0D; The leaf chlorophyll content was high in in vitro-grown plants under low light intensity. With increasing light intensity, a reduction in leaf chlorophyll content in vitro-grown plants was observed and at the later stages of acclimatization, it was comparable to that of the control. Variations in the rates of photosynthesis and transpiration in vitro-grown plants were observed in response to the changing environmental conditions. However, at the end of acclimatization, where the plants were ready to be transferred to the field, the physiological statuses of in vitro-grown coconut plants were comparable to that of nursery raised seedlings. The present study revealed that the embryo-cultured coconut plants could adjust well to the changing environmental conditions during acclimatization.

The promoter of a Brassica napus lipid transfer protein gene is active in a range of tissues and stimulated by light and viral infection in transgenic Arabidopsis.

cDNA and genomic clones encoding Brassica napus non-specific lipid transfer proteins (LTP) were isolated and sequenced. The encoded amino acid sequences were very similar to those reported previously for LTPs from B. napus and other species. Sequence information indicates that B. napus contains an LTP gene family. The 5'-flanking region of one gene, designated BnLTP, was fused to GUS and the fusion introduced into Arabidopsis. LTP transcripts and BnLTP-Gus expression were present predominantly in the epidermis of leaf and stem, consistent with the hypothesised function of LTPs in the deposition of cuticular or epicuticular waxes. However, GUS activity was detected in other tissues, including lateral root initials, anthers, stigmas and vascular tissues, which may suggest additional functions. LTP transcript levels in B. napus and Arabidopsis and BnLTP-GUS expression in transgenic Arabidopsis were stimulated by blue and red light but not UV-B. BnLTP promoter activity was also stimulated upon viral infection, at a time when the virus had spread systemically. No increase in expression was observed in response to cold or wounding.

Fatty acid and wax biosynthesis in susceptible and triallate-resistantAvena fatuaL.

The recent characterization of triallate-resistant lines of wild oat (Avena fatua L.) deficient in triallate sulfoxidation provides an experimental system to investigate and differentiate the effects of triallate and triallate sulfoxide on wax and lipid biosynthesis. Greenhouse applications of triallate dramatically reduced epicuticular wax deposition in susceptible (S) but not resistant (R) wild oats. Triallate treatment had no effect on in-vivo concentrations of C 12 to C 26 fatty acids and fatty alcohols in R plants, while elongated fatty acid fractions (C > 18) were significantly reduced in S plants. In contrast, treatment with triallate sulfoxide reduced in-vivo concentrations of elongated fatty acids equally in R and S, supporting the hypothesis that triallate sulfoxide is more inhibitory than triallate towards fatty acid elongases. Although de-novo synthesis of short-chain fatty acids was not affected by triallate or triallate sulfoxide in R or S plants, synthesis of elongated fatty acid fractions was dramatically reduced in S plants by triallate. Fatty acid biosynthesis in R and S plants was equally sensitive to triallate sulfoxide. The results support the idea that in-vivo triallate sulfoxidation is necessary for herbicidal activity, and confirm that reduced rates of triallate sulfoxidation confer resistance in R wild oats.

Effects of PEG-induced water stress onin vitro hardening of ‘Valiant’ grape

Polyethylene glycol was added to the rooting medium ofmicropropagated grape shoots to induce water stress. At the end of the rooting stage, plantlets treated with 2% polyethylene glycol were compared with untreated control plantlets and greenhouse-grown plants. Leaves of treated plantlets had the highest deposition of epicuticular wax, followed by those of the greenhouse and control. Stomatal index did not vary among treatments. However, differences in leaf epidermal cell configuration were observed among treatments. The morphological changes of treated plantlets, including substantial deposition of epicuticular wax and modified leaf surface anatomy were associated with increasedex vitro survival after four weeks in the greenhouse.

Effect of Soil Organic Matter on the Interaction Between Nicosulfuron and Terbufos in Corn (Zea mays)

Greenhouse and laboratory experiments were conducted to determine the effect of soil organic matter on the synergistic interaction between nicosulfuron, a sulfonylurea herbicide, and the insecticide terbufos in corn. Terbufos was applied infurrow at planting to soils containing 1, 3, and 5% organic matter and nicosulfuron was applied POST to corn at the three-leaf growth stage. The combination of terbufos and nicosulfuron reduced corn fresh weight 75, 45, and 41 % in soils containing 1, 3, and 5% organic matter, respectively. Terbufos increased [14C]nicosulfuron uptake into corn grown in both 1 and 5% organic matter soils. Terbufos decreased epicuticular leaf wax deposition on corn leaves by 35 and 18% in 1 and 5% organic matter soils, respectively. [14C]Nicosulfuron was completely metabolized after 24 h in the absence of terbufos. In the presence of terbufos, 19 and 11% of intact [14C]nicosulfuron remained 24 h after treatment while 11 and 6% remained after 48 h in the 1 and 5% organic matter soils, respectively. In vivo acetolactate synthase activity was reduced to 3 and 20% of control by nicosulfuron at 24 h and to 6 and 38% of control at 48 h, respectively, in the 1 and 5% organic matter soils that contained terbufos. These experiments indicated that soil organic matter is an important factor in determining the level of injury expected from the synergistic interaction between nicosulfuron and terbufos in corn.

Zinc Requirement for Stomatal Opening in Cauliflower.

Zn deficiency induced increases in epicuticular wax deposits, lamina thickness, degree of succulence, water saturation deficit, diffusive resistance, and proline accumulation and decreases in carbonic anhydrase activity, water potential, stomatal aperture, and transpiration in the leaves of cauliflower (Brassica oleracea L. var botrytis cv Pusa) plants. Restoration of Zn supply to the deficient plants increased stomatal aperture, transpiration, and carbonic anhydrase activity significantly within 2 h. However, leaf water potential in the Zn-deficient plants did not recover within 24 h after resupply of Zn. The guard cells in epidermal peels from the Zn-deficient leaves had less K+ than those from the controls. Stomatal aperture in the epidermal peels from Zn-deficient leaves was 64% less than in the controls when the epidermal strips were floated on 125 mM KCl. Supplementing the ambient medium 25 mM KCl with ZnCl2 enhanced stomatal aperture in both control and Zn-deficient peels, and the effect was significant in the latter. The observations indicate involvement of Zn in stomatal opening, possibly as a constituent of carbonic anhydrase needed for maintaining adequate [HCO3-] in the guard cells, and also as a factor affecting K+ uptake by the guard cells.

Carry-over of Morphological and Biochemical Characteristics Aßociated with Hyperflowering of Micropropagated Strawberries

Strawberry plants issued from shoots raised after a high number of subcultures (HNS) in vitro, which were previously characterized by an abnormal hyperflowering process ex vitro, were multiplied conventionally through runners for 8 generations, and then meristem tips re-entered in vitro for a low number of shoot subcultures (LNS). Such HNS-LNS vitroplants flowered abnormally abundantly as compared with always conventionally propagated N-LNS vitroplants, thus self-perpetuating a long term memory of an abnormal developmental pattern. The HNS-LNS hyperflowering vitroplants were also characterized by a carry-over of other biological (reduced growth habit), morphological (reduced hairiness and deposition of epicuticular wax, unifoliolate leaves prevailing) and biochemical (higher peroxidase activity) traits. They also proliferated in vitro at higher rates, which corresponded to higher endogenous levels of cytokinins and higher cytokinin/auxing ratios. Unifoliolate leaves and high cytokinin/auxin ratios are recognized criteria of rejuvenation. These characteristics of HNS strawberry vitroplants are carried-over in the next generations through heritable gene expression.

Mechanisms of deposition of epicuticular wax in leaves of broccoli, Brassica oleracea var. capitata L.

Broceeli (Brassika oleraceo L. var. capitata L.) leaf waxes were labelled with [2-14 Cjacetate 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 epicuriculur wax position. The hypothesis of wax-depositing pores running perpendicular to the leaf surface is not supported.

Comparative Uptake, Translocation, and Metabolism of Paraquat in Tolerant Kwangkyo and Susceptible Hood Soybean

The "Kwangkyo" and "Hood" cultivars of soybean [ Glycine max (L.) Merr.] are differentially sensitive to the herbicide paraquat. The margin of this intraspecific differential herbicide tolerance is narrow and Kwangkyo is about 10-fold more tolerant to paraquat than Hood soybean. The deposition of epicuticular wax on the surface of the first fully expanded trifoliolate was similar in both soybean cultivars and treatment with 1 m M paraquat did not influence the epicuticular wax content in any cultivar. Seedlings of Kwangkyo and Hood soybean absorbed comparable amounts of radioactivity following exposure to root-applied 14C-labeled paraquat for 24 hr. Most of the absorbed radioactivity remained in the roots of seedlings of both cultivars, but a greater amount of the recovered radioactivity translocated from roots to stems and leaves of the sensitive Hood soybean. Following feeding of the cut ends of their petioles with [ 14C]paraquat for 12 and 24 hr, excised trifoliolates of Kwangkyo soybean retained a greater portion of absorbed radioactivity in their petioles and translocated a smaller amount of radioactivity into the interveinal regions. By contrast, excised trifoliolates of Hood soybean retained a smaller portion of absorbed radioactivity in their petioles and released a higher amount of absorbed radioactivity into the interveinal regions. Extractable paraquat was not metabolized to any extent by tissues of either of the two cultivars and differential metabolism does not appear to play a role in the observed differential response of Kwangkyo and Hood soybean to paraquat. Overall, the results of the present study suggest that restricted mobility or a delayed release of paraquat into the mesophyll region is a likely basis for the observed tolerance of Kwangkyo soybean to the herbicide paraquat.

Epicuticular Wax on Johnsongrass (Sorghum halepense) Leaves

Studies were conducted to investigate the uniformity of epicuticular wax deposition on leaf blades of johnsongrass. Johnsongrass leaves grown under drought stress had greatly increased epicuticular wax weights compared to leaves from plants with adequate moisture, but relative humidity (95% vs. 40 ± 5%) had little effect on wax deposition. Wax weights decreased as leaves matured. Sections of lower leaf surfaces of young johnsongrass leaves tended to have more wax than sections of upper leaf surfaces, but weights were nearly equal on upper vs. lower leaf surfaces of older leaves. The narrow side of asymmetrical johnsongrass leaf blades often had more wax per unit area than the wide side. The area over the midvein contained more wax per unit area than either the narrow or wide side of the leaf blade. Greatest wax concentrations on individual leaves were over the midvein area near the leaf apex. Leaf blades of johnsongrass had more wax per unit area than leaves of corn or grain sorghum.

Comparative leaf morphology of young sporophytes of rheophyticOsmunda lancea and drylandO. japonica

Field and morphological observations were made of the young sporophytes of rheophyticOsmunda lancea and its related drylandO. japonica, and the rheophyte's adaptation in the early sporophytic stages was discussed. Mature plants ofO. lancea andO. japonica do not occur in dryland and rheophytic habitats, respectively, but their very young sporophytes rarely grow there. The young sporophytes ofO. lancea differ considerably from those ofO. japonica in having the relatively short petioles with thin-walled epidermal cells, early lamina partition, cuneate leaf- and pinna-base, oblique (not horizontal) lamina disposition, a fine network of spongy tissue in the 4th and older leaves, and dense epicuticular wax deposits on leaf epidermis. They seem to relate to the flexibility of petioles and the toughness and flood-tolerance of blades, and make the young sporophytes adapted to the rheophytic habitat.Osmunda japonica lacking those characteristics disappears from the rheophytic habitat during the early ontogenetic stages.