Protective and defensive roles of non-glandular trichomes against multiple stresses:structure-function coordination

As superficial structures,non-glandular trichomes,protect plant organs against multiple biotic and abiotic stresses.The protective and defensive roles of these epidermal appendages are crucial to developing organs and can be attributed to the excellent combination of suitable structural traits and chemical reinforcement in the form of phenolic compounds,primarily fl avonoids.Both the formation of trichomes and the accumulation of phenolics are interrelated at the molecular level.During the early stages of development,non-glandular trichomes show strong morphological similarities to glandular ones such as the balloon-like apical cells with numerous phenolics.At later developmental stages,and during secondary wall thickening,phenolics are transferred to the cell walls of the trichomes.Due to the diff use deposition of phenolics in the cell walls,trichomes provide protection against UV-B radiation by behaving as optical fi lters,screening out wavelengths that could damage sensitive tissues.Protection from strong visible radiation is also aff orded by increased surface light refl ectance.Moreover,the mixtures of trichome phenolics represent a superfi-cial chemical barrier that provides protection against biotic stress factors such as herbivores and pathogens.Although the cells of some trichomes die at maturity,they can modulate their quantitative and qualitative characteristics during development,depending on the prevailing conditions of the external biotic or abiotic environment.In fact,the structure and chemical constituents of trichomes may change due to the particular light regime,herbivore damage,wounding,water stress,salinity and the presence of heavy metals.Hence,trichomes represent dynamic protective structures that may greatly aff ect the outcome of many plant–environment interactions.     

泡桐属叶毛类型及对丛枝病的抗性

调查研究结果认为泡桐属叶毛类型有单枝毛、腺毛、叉状毛和树状毛4大类型.各类又有长柄、短柄或无柄之别.叶背有无叶毛和叶毛类型的不同对丛枝病的抗性有很大差异.叶背无毛或毛非常稀少对丛枝病高度感染,叶背毛为无柄（或几无柄）树状毛、短柄叉状毛和短柄、腺细胞小并无粘性腺毛的泡桐感病,叶背为不同类型的混合毛亦感病,但感病程度随长柄和短柄毛的比例不同而有所差异.叶背毛为较稠密的长柄树状毛、长柄叉状毛、长柄单枝毛和长柄、腺细胞大的粘性腺毛的泡桐为高度抗病.抗病的原因是抗传毒介体昆虫.     

Classification of Azolla spp., section Azolla

Summary Azolla accessions (section Azolla) from the germplasm collections of the International Rice Research Institute and Washington State University were fingerprinted and classified by enzyme electrophoresis and leaf trichome morphology. A. filiculoides was enzymatically distinctive and also reliably identified by its prominent one-celled trichomes. Neotropical accessions labelled as A. filiculoides proved to be members of other species. Two groups of isolates were designated A. rubra, but those from Japan were identified as A. filiculoides. The A. rubra of Australia-New Zealand was biochemically unique and possessed less protuberant trichomes than A. filiculoides. A. microphylla, A. mexicana, and A. caroliniana were phenetically similar, but a. microphylla was identifiable from the others in the banding patterns of certain enzymes. A. mexicana and A. caroliniana were closely related enzymatically. The two-celled leaf trichomes of these three species were similar in size and shape.     

Contradictions in host plant resistance to pests: spider mite (Tetranychus urticae Koch) behaviour undermines the potential resistance of smooth-leaved cotton (Gossypium hirsutum L.)

BACKGROUND: Two‐spotted spider mites (Tetranychus urticae Koch) oviposit near leaf veins or in leaf folds on the undersides of cotton (Gossypium hirsutum L.) leaves where the humid boundary layer offers protection from desiccation. The authors predicted that the boundary layer of glabrous cotton leaves should be shallower than that of hairy leaves, providing some resistance to mites. The dynamics of mite populations, leaf damage, leaf gas exchange and crop yield on two leaf hair isolines (smooth versus hairy) in two genetic backgrounds was assessed. RESULTS: Mite colonies developed faster on the hairy leaf isolines, but leaf damage per mite was higher in smooth leaf isolines, indicating more intense damage. A 50% reduction in photosynthesis on the hairy isolines required 1.8 times more mites than smooth leaves. The yield of cotton was reduced in + mite treatments, but the magnitude of reduction was similar for hairy and smooth isolines. CONCLUSION: Paradoxically, the relative inhospitality of glabrous leaves may have induced mites to concentrate in protected leaf sections, causing more localised and more severe damage, negating the yield benefits from fewer mites. These results highlight interactions between leaf microenvironment, pest behaviour and plant productivity that may have implications for other instances of plant resistance. Copyright © 2010 Society of Chemical Industry     

Stage of development affects penetration of calcium chloride into apple fruits

Using young fruits or fruit segments, rates of penetration of ⁴⁵CaCl₂ across apple fruit cuticles (Malus x domestica) were studied during fruit development in two consecutive years (’?Golden Delicious’ in 2000, ’?Cox Orange Pippin’ and ’?Boskoop’ in 2001). The aqueous donor solutions contained 5 g l^—1 CaCl₂ and 0.2 g l^—1 Glucopon 215 CSUP as wetter. A droplet (5 μl) was applied to each fruit disc and allowed to dry within 1 h. Amounts penetrated were estimated immediately after droplet drying (0 h) and after 6 and 24 h penetration, respectively. Temperature during penetration was 20 ?C and 100 % humidity was maintained throughout the experiment, once the droplet had dried. Rates of penetration were greatly affected by the stage of fruit development. With all varieties tested, highest rates were measured during the early stages of fruit development (before June drop) when approx. 100 % of the CaCl₂ applied penetrated within 24 h. After June drop, when trichomes had vanished and most stomata developed into lenticels, penetration rates decreased rapidly and large variability among the samples developed. This pattern was similar with all three varieties. The involvement of trichomes, stomata, and lenticels as preferential sites of penetration of calcium chloride across the apple fruit cuticles is discussed. Using a model calculation, it is argued that ten or more spray applications are needed to significantly increase calcium contents of apples. This has two causes: Only a small fraction of the spray liquid is intercepted by the fruits, and penetration can be rather slow.     

烤烟EMS诱变后代高香气突变体筛选

为筛选高香气且品质较优的烤烟后代,以中烟100为材料,采用EMS诱变技术对中烟100种子进行处理,筛选出2个叶面腺毛密度大的突变体材料,通过田间试验,对其叶面腺毛密度、叶面化学成分、烤后化学成分、香气物质含量和感官质量评吸等指标进行评估,并与正常中烟100后代和NC89进行对照。研究结果表明,EMS-2诱变株系腺毛密度最大,为65.55个/mm ²,分别是中烟100（37.19个/mm ²）和NC89（56.06个/mm ²）的1.8和1.2倍;叶面化学成分分析结果表明,EMS-1诱变株系西柏烷类和烷烃类含量最多,分别为57.18、5.16mg/m ²,EMS-2突变株系蔗糖酯类物质分泌较旺盛,含量最多,为0.33mg/m ²;烤后样化学成分分析结果表明,EMS-2突变株系化学成分含量较协调,且香气成分含量最多,达到890.32μg/g,分别比中烟100和NC89增加34.5%和29.0%;结合对诱变后代的感官评价,得出结论：诱变株系综合品质较好,可提高烟叶质量,EMS-2综合品质最好,可以作为待选株系进行下一步品种选育。     

野菊和神农香菊毛状体及叶片表面分泌物的比较

本研究以野菊(Dendranthema indicum)和神农香菊(D.indicumvar.aromaticum)为研究对象,对比分析了其叶片的表皮毛形态、密度以及叶片表面分泌物种类和含量。结果表明,其叶片表皮毛主要有两种类型,一类是没有分泌功能的T-形非腺毛,一类是具有分泌功能的头状腺毛。T-形非腺毛在上下表皮的密度差异不大,而头状腺毛差异较大,主要集中在叶片的下表皮。两种植物材料叶片表面分泌物里共分析出73种化合物,其中大部分为萜类及其衍生物,共有的化合物有18种;野菊和神农香菊中分别分析出48、43种化合物,分别占分泌物总相对含量的90.96%和84.33%。     

Research inSolanum spp. of sources of resistance to the potato tuber mothPhthorimaea operculella (Zeller)

Summary The potato tuber moth (PTM) represents a dangerous pest on potato crop in Italy, spreading out from southern areas to central and northern areas. Introductions ofSolanum berthaultii, S. commersonii, S. pinnatisectum, S. sparsipilum, S. spegazzini, S. sucurense, S. tarijense wild species andS. tuberosum × S. berthaultii hybrids were evaluated for resistance to a PTM population isolated from a field in central Italy, by means of an antibiosis test on tubers in the laboratory and of an antixenosis trial in the field. SeveralS. sparsipilum andS. pinnatisectum clones showed an antibiosis effect on larval survival and antixenosis of the aerial and the hypogeal parts of the plant. In the field, the genotypes with leaf glandular trichomes did not revcal the expected antixenosis effect of the acrial part of the plant.     

UV–B辐射对神农香菊叶片表皮毛及其分泌物的影响

以神农香菊(Dendranthema indicum var.aromaticum)为材料,用紫外光UV–B对其进行辐射处理,处理时间分别为0(CK)、1、3、5、7 d,研究其对叶片表皮毛形态、密度和叶片表面分泌物的影响。结果表明:UV–B处理后的头状腺毛中部出现不规则凹陷,甚至扭曲;"T"形非腺毛出现顶细胞破裂、脱落现象;头状腺毛和"T"形非腺毛的密度均随处理天数的增加,呈先增加后减少的趋势,两者均在处理1 d时达最大,此时叶尖、叶中、叶基的头状腺毛密度每视野分别为16.00、13.67、18.67根,叶片下表皮的"T"形非腺毛密度每视野达43.84根;叶片表面分泌物中α–蒎烯、α–荜澄茄油烯的相对含量变化不明显,而杜松萜烯、1–石竹烯的相对含量变化较大,均在处理3 d时相对含量达到最高,分别为19.45%和14.71%;樟脑类物质和醇酮类物质的相对含量呈现先升高后降低的变化趋势,在第1天或第3天达到最大值,第7天降到最低。     

Susceptibility of sunflower inbreds to Melanagromyza minimoides in Argentina and potential association with plant resistance traits

Seed-feeding by larvae of the mosquito head fly, Melanagromyza minimoides, can substantially reduce yields of late-planted sunflower in South America and its management with insecticides or early-planting has other undesirable costs. Evaluation of inbred lines over three seasons indicated differences in the emergence of adult flies, particularly between restorer (male) and maintainer (female) lines used for hybrid seed production; when fly emergence (≈damage) was adjusted for differences in head size (i.e. to flies/100 cm²), restorer lines averaged 3–12 times more damage than maintainer lines. Fly emergence in each of two seasons was tested for correlations with three sunflower traits (glandular trichome number, pericarp strength, and sesquiterpene lactone content) believed to provide host plant resistance to other insects. In one of two years, fly emergence was negatively correlated with the relative amount of sesquiterpene lactones in florets of the tested lines. Also, among maintainer lines, severity of infestation was much greater in multi-headed inbreds compared to single-headed lines. Additional research is needed to establish the cause(s) of reduced susceptibility of inbreds and whether parental lines influence M. minimoides damage to hybrids.