不同小麦品种（系）叶片表面蜡质对两种麦蚜取食的影响

采用气质联用(GC-MS)和生物测定法,探讨了不同小麦品种(系)叶片表面蜡质对麦长管蚜和禾谷缢管蚜取食的影响.结果表明:SN80、SN18和ZM12叶片表面蜡质对2种蚜虫取食具有刺激作用,而SN87叶片表面蜡质无刺激作用.对4种小麦材料叶片表面蜡质进行GC-MS分析发现,其表面蜡质化学组分有所不同,但主要组分均为长链烷烃,其它组分包括7-十四碳烯、8-十五烷酮、十四烷酸乙酯和十六烷酸乙酯等.生物测定结果表明:长链烷烃(>C17)、7-十四碳烯及8-十五烷酮对两种蚜虫取食具有显著的刺激作用;而乙基柠檬酸、十四烷酸乙酯和十六烷酸乙酯对麦长管蚜取食无刺激作用;十四烷酸乙酯和十六烷酸乙酯对禾谷缢管蚜取食也无刺激作用.     

Composition of leaf surface waxes of Triticum species: Variation with age and tissue

The composition of cuticular wax from plants of spring wheat (varieties Selkirk and Manitou) and of durum wheat (variety Stewart 63) at various stages of growth, and of wax from different parts of the plants varies considerably. Wax was analysed, without preliminary separation, by GLC using Dexsil 300 as liquid phase. Alcohols are major components of wax from leaf blades and β-diketones are major components of wax from leaf sheaths, especially the flag leaf sheath. Glaucousness of the leaf sheath is due to the high β-diketone content. In the first 50 days after germination, before sheaths and flag leaf are completely developed, the major component is octacosanol (> 50%). At 66 days, when sheath development is complete, β-diketone content is greatest. Hydrocarbon composition differs for wax from leaf blade and leaf sheath and also for different leaf blades and between adaxial and abaxial sides of the flag leaf. From 66 to 100 days ester content of wax increases, especially in Selkirk wheat, apparently due to formation of wax containing high proportions of esters of trans-α,β-unsaturated C₂₂ and C₂₄ acids. The content of these acids in the free fatty acids and of diesters based on these acids also increases during this period.     

Leaf hydrocarbons of Phacelia species (hydrophyllaceae)

Whole leaf hydrocarbons of six species of Phacelia were investigated for their variability among natural Californian populations, and for adaptive     

Influence of leaf epicuticular waxes from cerrado species on substrate selection byAtta sexdens rubropilosa

The influence of leaf epicuticular waxes of nine woody species from cerrado (a savanna ecosystem of Brazil) on the foraging behavior of the leaf-cutting antAtta sexdens rubropilosa Forel, 1908 (Formicidae, Attini) was investigated. Some waxes showed neither inhibitory nor attractive effect over a series of tests, while a second group caused a delayed rejection. Waxes of two species were shown to be strongly deterrent to the ants. Since different waxes caused different responses, it is concluded that their chemical composition, rather than hydrophobicity or mechanical constraints, accounts for the observed effects. Plant species with leaves rejected by the ants did not necessarily have repellent waxes. On the other hand, no species with acceptable leaves yielded waxes with deterrent effects.     

Leaf wax constituents of some myrtaceous species

Eucalyptin and 8-desmethyleucalyptin have been isolated from the leaf wax coatings of several species of Eucalyptus, from Syncarpia glomulifera, Lophostemon confertus and an Angophora hybrid indicating that C-methylated flavones may be fairly distinctive of the family Myrtaceae. Ursolic acid has been isolated from the leaf waxes of E. youmanii, S. glomulifera, Leptospermum petersonii and Melaleuca quinquenervia, friedelin from Lophostemon confertus and 4,6-dimethoxy-2-hydroxyacetophenone from E. michaeliana.     

Taxonomic significance of the distribution of constituents of leaf cuticular waxes of Croton species (Euphorbiaceae)

Foliar epicuticular waxes of specimens of 13 Croton species native in Brazil were extracted. The fractions containing alkanes and primary alcohols were isolated by preparative thin layer chromatography. Derivatized n-primary alcohols were identified by gas chromatography (GC) coupled with mass spectrometry and n-alkanes by GC and comparison with known standards. Relative abundances were estimated by GC coupled with flame ionization detector. The distribution of constituents of both classes was analyzed by cluster analysis, using the UPGMA method and Euclidean distances. The chemical affinities among species were compared with published data of molecular phylogenetic relationships. The distribution of n-alkanes and primary alcohols were shown to be useful markers of Croton species. Primary alcohols were more consistent than n-alkanes for species fingerprinting.     

Decline of photosynthetic capacity with leaf age in relation to leaf longevities for five tropical canopy tree species

The effect of leaf aging on photosynthetic capacities was examined for upper canopy leaves of five tropical tree species in a seasonally dry forest in Panama. These species varied in mean leaf longevity between 174 and 315 d, and in maximum leaf life span between 304 and 679 d. The light-saturated CO2 exchange rates of leaves produced during the primary annual leaf flush measured at 7-8 mo of age were 33-65% of the rates measured at 1-2 mo of age for species with leaf life span of < 1 yr. The negative regression slopes of photosynthetic capacity against leaf age were steeper for species with shorter maximum leaf longevity. In all species, regression slopes were less steep than the slopes predicted by assuming a linear decline toward the maximum leaf age (20-80% of the predicted decline rate). Maximum oxygen evolution rates and leaf nitrogen content declined faster with age for species with shorter leaf life spans. Statistical significance of regression slopes of oxygen evolution rates against leaf age was strongest on a leaf mass basis (r = 0.49-0.87), followed by leaf nitrogen basis (r = 0.48-0.77), and weakest on a leaf area basis (r = 0.35-0.70).     

The determination of n-alkanes in the cuticular wax of leaves of Ludwigia adscendens L

An n-hexane extract of fresh, mature leaves of Ludwigia adscendens, containing a thin layer of epicuticular waxes, has been analysed for the first time by TLC, IR and GC using standard hydrocarbons. The leaves contained 22 identified long chain (C15-C36) n-alkanes, accounting for 74.27% of the hydrocarbons present, and an unknown number of unidentified branched chain alkanes. The predominant n-alkane was C25 (11.02%), whilst C18 (7.62%), C20 (6.14%), C29 (5.36%) and C27 (5.29%) n-alkanes were moderately abundant: the C35 homologue was present only in minor amounts (0.22%).     

The effects of Kloeckera apiculata on the cuticular waxes of navel orange fruit

Kloeckera apiculata 34-9 was selected from the rhizosphere soil for its high efficacy in controlling citrus green and blue mold. In this study, the effect of the antagonistic yeast K. apiculata on citrus cuticular wax was investigated in ripening Newhall navel orange (Citrus sinensis L. Osbeck). Our results show that K. apiculata triggers the production of cuticular waxes and surface wax morphology changes in the fruit surface. 15 K. apiculata-responsive differentially expressed genes (DEGs) were identified for wax metabolism by using the Affymetrix citrus genome GeneChip. Using GC–MS, 46 wax compounds were found in the Newhall fruit surface. On one hand, esters including docosanoic acid, 1,2,3-propanetriyl ester and 9-hexadecenoic acid, 9-octadecenyl ester were up-regulated approximately twofold in the treatment condition compared with the control; and on the other hand, the fatty acids and fatty alcohols decreased by 74.4% and 72.3%, respectively, in the treatment condition. The new wax production and increased hydrophobicity of the Newhall surface resulting from the treatment may influence spore adhesion and germination. Furthermore, the response of the fruit waxes to the K. apiculata stimulus is likely to be regulated by intra-cellular H₂O₂ signaling. This study demonstrated the response fruit waxes to K. apiculata in Newhall navel oranges, thus providing new clues that aid our understanding of the mechanisms of action of antagonistic yeasts in postharvest fruits.     

Plant surface lipid biosynthetic pathways and their utility for metabolic engineering of waxes and hydrocarbon biofuels

Due to their unique physical properties, waxes are high-value materials that are used in a variety of industrial applications. They are generated by chemical synthesis, extracted from fossil sources, or harvested from a small number of plant and animal species. As a result, the diversity of chemical structures in commercial waxes is low and so are their yields. These limitations can be overcome by engineering of wax biosynthetic pathways in the seeds of high-yielding oil crops to produce designer waxes for specific industrial end uses. In this review, we first summarize the current knowledge regarding the genes and enzymes generating the chemical diversity of cuticular waxes that accumulate at the surfaces of primary plant organs. We then consider the potential of cuticle biosynthetic genes for biotechnological wax production, focusing on selected examples of wax ester chain lengths and isomers. Finally, we discuss the genes/enzymes of cuticular alkane biosynthesis and their potential in future metabolic engineering of plants for the production of renewable hydrocarbon fuels.     

Composition of suberin-associated waxes from the subterranean storage organs of seven plants

The waxes associated with the suberin in the periderm of the underground storage organs of parsnip (Pastinaca sativa L.), carrot (Daucus carota L.), rutabaga (Brassica napobrassica Mill.), turnip (Brassica rapa L.), red beet (Beta vulgaris L.), sweet potato (Ipomoea batatas L.) and potato (Solanum tuberosum L.) were isolated, fractionated into hydrocarbon, wax ester, free fatty alcohol and free fatty acid fractions, and analyzed by combined gas chromatography and mass spectrometry. The amount of wax extracted from the periderm of the storage organs ranged from 2 to 32 μg/cm². The hydrocarbons from the suberin layer have a broader chain-length distribution, a predominance of shorter carbon chains, and a higher proportion of even-numbered carbon chains than the leaf alkanes from the same plants. The major components of the free and esterified fatty alcohols and fatty acids have an even number of carbon atoms, and are similar in chain-length distribution to their counterparts found covalently attached to the suberin polymers; however, these suberin components are shorter in chain length than their cuticular analogues from the leaves. Also extracted from the storage organs were polar components which included fatty alcohols and fatty acids in a conjugated form, and ω-hydroxy acids and dicarboxylic acids. Evidence is presented that removal of the wax from the periderm of whole storage organs results in a decrease in diffusion resistance to moisture. Scientific Paper No. 5516, Project 2001, College of Agriculture Research Center, Washington State University, Pullman, WA 99164, USA     

Epidermal conductance in different parts of durum wheat grown under Mediterranean conditions: the role of epicuticular waxes and stomata

Abstract. Epidermal (non-stomatally-controlled) conductance from the fourth leaf, first node leaf, flag leaf and ear of durum wheat (Triticum turgidum var durum L.) grown under Mediterranean field conditions has been measured, along with leaf stomatal frequency and the amount and distribution of epicuticular waxes. Measurements were carried out on varieties and land-races from the Middle East, North Africa, ‘Institut National de la Recherche Agricole’ (INRA) and ‘Centra Internacional de Mejora de Maiz y Trigo’ (CIMMYT). Significant differences were observed among genotypes in the epidermal conductances (g_e) of the four organs. For each of the four organs tested, genotypes from the Middle East and CIMMYT showed higher g_e. values than those from North Africa and INRA. Ears showed epidermal conductances that were more than four times higher than those of leaves when g_e. values were expressed per unit dry weight. The amount of epicuticular waxes was higher in the fourth leaves, intermediate in the first node and flag leaves and lower in the ears. For each organ, g_e differences among genotypes were unrelated with the amount of epicuticular waxes. Removal of epicuticular waxes by dipping the organs into chloroform significantly increased the epidermal conductance for the fourth and first node leaves and the ear. However, this did not occur for the flag leaf. For the fourth leaf, g_e of intact leaves and g_e of leaves in which epicuticular waxes were removed were unrelated (r = -0.265). The regression coefficient of this relation for the first node and flag leaves showed values of 0.666 and 0.650 (P > 0.05), respectively, and values were even higher in the ear (r > m 0.892, P > 0.01). Scanning electron microscope analysis showed that wax bloom decreased from the fourth leaf to the flag leaf, whereas the extent of amorphous wax increased. Wax bloom in leaves consisted mainly of deposits of thin wax plates. In the ears and the adaxial surface of flag leaves, fibrillar waxes predominated. In the first node and flag leaves, the wax deposits on the adaxial side cover the surface of the leaf more densely and uniformly than those on the abaxial side. There was no significant correlation between g_e and total stomatal density, or between g_e and either adaxial or abaxial stomatal density for any sample of the three different leaves. The contribution of epicuticular waxes plus total stomatal frequency only explained 42.4, 11.8, 28.3 and 16% of g_e (per unit leaf area) variations for the fourth leaf, first node leaf, flag leaf and the combined variation of the three leaves together, respectively. From these results, it is concluded that complex interrelationship between different morphophysiological characteristics probably control g_e differences among genotypes and that these interrelationships differ for each different plant part.     

Ontogenetic variations in the composition of peach leaf wax

The composition of the epicuticular waxes from the adaxial and abaxial surfaces of peach leaves varies considerably during one season's growth. Triterpenoid acids are major components 84–95% of the waxes from the youngest leaves but the proportions of these constituents decrease as the leaves expand. The waxes from the abaxial surfaces of fully expanded leaves consist primarily of hydrocarbons (C_22–C34) and triterpenoid acids, whereas the adaxial surface waxes also contain large proportions of primary alcohols (C₂₆-C₃₄) and esters (C₄₂-C₅₂). The latter include sitosteryl esters of hexacosanoic, octacosanoic and eicosanoic acids. Variations were also noted between fully expanded leaves of different ages, the abaxial surface waxes of the oldest leaves containing the highest proportions of hydrocarbons, whilst the wax from the adaxial surface of the corresponding leaves contained the largest amounts of esters, sitosterol and hydrocarbons.     

Comparative alkane chemistry of Parthenium argentatum (guayule) and some F1 hybrids

The leaf alkanes of Parthenium argentatum (guayule), P. tomentosum var. stramonium, P. fruticosum var. trilobatum, and the first filial (F₁) generations obtained from crosses with guayule were investigated by GC and mass spectrometry and shown to be useful in chemotaxonomic studies. The identified n-alkanes ranged from C₁₉ to C₄₀ with either n-C₂₉ or n-C₃₁ as the main component. The alkane chemistry of guayule with n-C₃₁ being the main component predominated in most of the F₁ hybrids. The presence of iso-branched alkanes (C₂₇, C₂₉, C₃₁) in P. tomentosum and its hybrids could be detected by GC/MS. These preliminary investigations indicate that epicuticular wax alkanes can be useful in inheritance studies of guayule and its hybrids.     

Homologous very-long-chain 1,3-alkanediols and 3-hydroxyaldehydes in leaf cuticular waxes of Ricinus communis L

Surface extracts from primary leaves of Castor bean were found to contain 1.8 microg cm(-2) of cuticular waxes. The mixture comprised alkanes (C(26)-C(29)), primary alcohols (C(22)-C(38)), aldehydes (C(26) and C(28)), fatty acids (C(20)-C(34)) and triterpenoids (lupeol, beta- and alpha-amyrin). Besides, a series of n-alkane-1,3-diols was detected, with chain lengths ranging from C(22) to C(28), a strong predominance of even-numbered homologs, and a maximum for hexacosane-1,3-diol. Seven other compounds were assigned to a novel class of wax constituents and identified as homologous unbranched 3-hydroxyaldehydes ranging from C(22) to C(28). As the chain length distribution of this series closely paralleled the homolog pattern of 1,3-diols, it seems likely that both compound classes are biosynthetically related.     

冠层部位和叶龄对红松光合蒸腾特性的影响

利用Li-6400便携式CO2/H2O红外气体分析仪测定了红松不同冠层部位和叶龄针叶的光合蒸腾特性及其环境影响因子.结果表明:冠层部位和叶龄显著地影响最大净光合速率(Pmax)、光饱和点(LSP)、光补偿点(LCP)、表观最大量子效率(α)、蒸腾速率(Tr)和比叶面积(SLA),但对水分利用效率(WUE)影响不显著.随着冠层部位的下降和叶龄的增加,红松针叶的Pmax逐渐下降,其平均值变动在6·55～9·05μmol·m-2·s-1之间.不同冠层部位和叶龄针叶的LSP和LCP的差异很大,以树冠中部针叶对弱光和强光的利用能力最大.Tr随着冠层部位的下降而降低;不同叶龄针叶的Tr在1·37～1·59mmol·m-2·s-1之间变化.不同部位和叶龄红松针叶的Tr和光合有效辐射存在极显著正相关关系(R2=0·967).红松的WUE与净光合速率紧密相关(R2=0·860).随冠层部位的上升和叶龄的增大,红松针叶的SLA递减,分别在6·61～8·41m2·kg-1和6·65～8·38m2·kg-1之间波动.