Changes in cotton leaf chemistry induced by volatile elicitors

Cotton (Gossypium hirsutum) leaves were exposed for 7 days to volatile chemicals originating from Aspergillus flavus-infected cotton leaves, A. flavus cultures or mechanically damaged cotton leaves. Volatiles from A. flavus-infected leaves triggered significant increases of 52 and 34% in phloroglucinol-reactive compounds in wounded or undamaged cotton leaves, respectively. Increased production of heliocides (C₂₅ terpenoid aldehydes) were found in the volatile recepient wounded or undamaged cotton leaves. The heliocides are natural insecticides presumed localized in the subepidermal pigment glands in leaves. Myrcene, a volatile precursor of heliocide H₂, also caused significant increases in heliocide production when leaves were exposed to the volatilized chemical.     

Characteristics and inheritance of chlorophyll mutations inPhaseolus mungo

Viable mutations affecting chlorophyll production in black gram (Phaseolus mungo L.) were recovered following treatments with X-rays and ethyl methanesulphonate singly or in combination. Of these theviridis mutant was characterized by viridine green colour of all the leaves and reduced plant size. inchlorotica the emerging leaves were initially yellowish green which gradually changed to dark green at flowering. The terminal 2–3 leaves always remained yellowish green inchlorina-terminalis whereas inchlorina-virescence the emerging leaves were yellowish green that changed to dark green at flowering. Inalbo-virescence the first 3–5 leaves at emergence were white in which small irregular green dots or patches often developed. The subsequent leaves were normal green. The emerging trifoliate leaves ofaureo-virescence were light green which turned to turtle green within a week. It was established thatviridis, chlorotica, chlorina-terminalis, chlorina-virescence, andalbo-virescence mutants were conditioned by a single receissive gene, in each case. Theaureo-virescence character was found to be inherited through the cytoplasm.     

Habitat selection in two species of aquatic hyphomycetes

Two species of aquatic hyphomycetes,Tetracladium marchalianum andTricladium splendens, were isolated from decaying leaves in a stream.T. marchalianum was abundant on alder leaves but absent on beech leaves, which were dominated byT. splendens. It was hypothesized that differences in some chemical key factors in the leaves would account for differences in the distribution of the 2 species. In the experiment designed to test the hypothesis, combinations of sterilized leaves and isolated fungi were used. Differences in growth of FDA active mycelium were related to differences in leaf weight loss;T. splendens decomposed beech leaves andT. marchalianum decomposed alder leaves. Extracellular protease activity corresponded with these trends but there was no detectable protein loss in the leaves. Both fungi showed a nitrogen demand, and hydrolysis of leaf proteins was complemented with absorption of free amino acids and ammonium. High concentrations of free amino acids modified the pattern for habitat selection so thatT. splendens grew substantially on alder leaves andT. marchalianum colonized beech leaves. No protease activity was, however, found fromT. marchalianum on beech leaves, and it is concluded that a more general metabolic inhibition prevents extensive growth of this species on beech leaves. The low natural abundance ofT. splendens on alder leaves, where it may grow well, may be a consequence of a specific protease inhibition and competition from other species.     

Rapid and Pervasive Occupation of Fallen Mangrove Leaves by a Marine Zoosporic Fungus

Samples of leaves of red mangrove (Rhizophora mangle) were incubated on an agar medium selective for pythiaceous oomycetes. Leaves on trees above the water did not contain oomycetes. Marine oomycetes, principally Phytophthora vesicula, had colonized leaves within 2 h of leaf submergence, probably finding them by chemotaxis. The frequency of occurrence of P. vesicula in submerged leaves reached 100% within 30 h of submergence. By 43 h most, if not all, parts of leaves were occupied, and surface treatment with a biocide indicated that leaves were occupied internally. Frequencies of P. vesicula remained near 100% through about 2 weeks of submergence and then declined to about 60% in older (≥4 weeks) leaves. Leaves of white mangrove (Laguncularia racemosa) were also extensively occupied by P. vesicula after falling into the water column, but decaying leaves of turtlegrass (Thalassia testudinum) were not colonized by oomycetes. Ergosterol analysis indicated that the standing crop of living, non-oomycete (ergosterol-containing) fungal mass in submerged red-mangrove leaves did not rise above that which had been present in senescent leaves on the tree; decaying turtlegrass leaves had an ergosterol content that was only about 2% of the maximum concentration detected for red-mangrove leaves. These results suggest that oomycetes are the predominant mycelial eucaryotic saprotrophs of mangrove leaves that fall into the water column and that for turtlegrass leaves which live, die, and decompose under submerged conditions, mycelial eucaryotes make no substantial contribution to decomposition.     

Chlorophyll, Ribulose-1,5-diphosphate Carboxylase, and Hill Reaction Activity in Developing Leaves of Populus deltoides

The synthesis of chlorophyll and ribulose diphosphate carboxylase as well as the development of Hill reaction activity were followed in expanding Populus deltoides leaves and related to photosynthetic patterns. Total chlorophyll, which was not correlated with photosynthetic rate in expanding leaves, decreased slightly with age in very young leaves, due to a decrease in chlorophyll b, but then increased linearly. The ratio of chlorophyll a to b, which rose sharply in young leaves, was highly correlated with the onset of net photosynthesis. Hill reaction activity was very low in young leaves and did not increase significantly until leaves were about half expanded. Ribulose diphosphate carboxylase activity increased in a sigmoid fashion with leaf ontogenesis and closely paralleled development of the photosynthetic system. The study demonstrates the importance of chlorophyll a and Calvin cycle enzyme synthesis to photosynthetic development in expanding leaves.     

A comparison of the volatile oils of mature versus young leaves of Juniperus scopulorum: Chemosystematic significance

The volatile oils of leaves of clonal, greenhouse grown trees of J. scopulorum cv. platinum were examined from young (juvenile or whip leaves) and mature (adult or scale leaves) foliage. Of 36 compounds subjected to analysis of variance, 19 showed significant differences between young and old leaves. In general, the hydrocarbon terpenoids were higher in concentration in new leaves while the oxygenated compounds were higher in the older leaves. This same pattern has been reported in several other gymnosperms. Numerical taxonomy using data on the volatile oils from young and mature leaves yielded the same relative similarities among the five trees examined. Surprisingly, the plants were more similar in the volatile oil from the young leaves than from the mature leaves. The mixing of different ages of leaves in samples for chemosystematic studies is, however, to be discouraged     

Single-Leaf Resolution of the Temporal Population Dynamics of Aureobasidium pullulans on Apple Leaves

The abundance of phylloplane microorganisms typically varies over several orders of magnitude among leaves sampled concurrently. Because the methods traditionally used to sample leaves are destructive, it has remained unclear whether this high variability is due to fixed differences in habitat quality among leaves or to asynchronous temporal variation in the microbial population density on individual leaves. We developed a novel semidestructive assay to repeatedly sample the same apple leaves from orchard trees over time by removing progressively more proximal ~1-cm-wide transverse segments. Aureobasidium pullulans densities were determined by standard leaf homogenization and plating procedures and were expressed as CFU per square centimeter of segment. The A. pullulans population densities among leaves were lognormally distributed. The variability in A. pullulans population densities among subsections of a given leaf was one-third to one-ninth the variability among whole leaves harvested concurrently. Sequential harvesting of leaf segments did not result in detectable changes in A. pullulans density on residual leaf surfaces. These findings implied that we could infer whole-leaf A. pullulans densities over time by using partial leaves. When this successive sampling regimen was applied over the course of multiple 7- to 8-day experiments, the among-leaf effects were virtually always the predominant source of variance in A. pullulans density estimates. Changes in A. pullulans density tended to be synchronous among leaves, such that the rank order of leaves arrayed with respect to A. pullulans density was largely maintained through time. Occasional periods of asynchrony were observed, but idiosyncratic changes in A. pullulans density did not contribute appreciably to variation in the distribution of populations among leaves. This suggests that persistent differences in habitat (leaf) quality are primarily responsible for the variation in A. pullulans density among leaves in nature.     

Diversity and ubiquity of xylariaceous endophytes in live and dead leaves of temperate forest trees

To test the hypothesis that xylariaceous endophytes were ubiquitous on live and dead leaves of various tree species in the field, xylariaceous fungi were isolated from live leaves and bleached and nonbleached portions of dead leaves of a total of 94 tree species in a cool temperate forest in Japan. The biodiversity of xylariaceous endophytes was evaluated as the richness of operational taxonomic units (OTUs) determined by phylogenetic analysis of the nucleotide sequence of the D1/D2 region of the LSU rDNA of fungal isolates. A total of 326 isolates of xylariaceous fungi were isolated from live and dead leaves and classified into 15 OTUs. The three major OTUs, Xylaria sp.1, Nemania sp., and Biscogniauxia sp., accounted for 94% (308 isolates) of the total number of isolates, and were isolated from various live and dead leaves. Xylaria sp.1 was frequently encountered on bleached portions (which were produced due to the selective decomposition of lignin) of dead leaves of broad-leaved deciduous tree species. The results suggest that xylariaceous endophytes did not show host specificity and had a saprobic phase on dead leaves in their life cycles and that Xylaria sp.1 was capable of decomposing lignin in the field conditions.     

Chemotype variation of the weed Melaleuca quinquenervia influences the biomass and fecundity of the biological control agent Oxyops vitiosa

Host plant nutritional and non-nutritional variability can have a significant effect on herbivore populations by influencing survival, larval performance, and fecundity. The effect of chemical and physical variation of the leaves of two chemotypes of the weed Melaleuca quinquenervia was determined on the biomass and fecundity of the biological control agent Oxyops vitiosa (Coleoptera: Curculionidae). M. quinquenervia chemotypes were distinguished by the principal terpenoids E-nerolidol and viridiflorol using gas chromatography and mass spectroscopy. Not only were the terpenoid profiles of the two chemotypes different but the viridiflorol leaves had greater toughness (1.2-fold) and reduced nitrogen (0.7-fold). When the larvae and adults were fed leaves of the E-nerolidol chemotype increased adult biomass (1.1-fold) and fecundity were found (2.6- to 4.5-fold) compared with those fed leaves of the viridiflorol chemotype. Regardless of the larval diet, when adults were fed the E-nerolidol chemotype leaves they had greater egg production compared with those adults fed the viridiflorol leaves. Moreover, adult pre-oviposition period was extended (1.5-fold) when individuals were fed the viridiflorol leaves compared with those fed the E-nerolidol leaves. By rearing the O. vitiosa weevil on the more nutritious chemotype plants these results assisted in the mass production and establishment of the M. quinquenervia biological control agent.     

Development and Leaf Consumption by Spodoptera cosmioides (Walker) (Lepidoptera: Noctuidae) Reared on Leaves of Agroenergy Crops

Spodoptera cosmioides (Walker) (Lepidoptera: Noctuidae) is a polyphagous pest that threatens more than 24 species of crop plants including those used for biodiesel production such as Ricinus communis (castor bean), Jatropha curcas (Barbados nut), and Aleurites fordii (tung oil tree). The development and leaf consumption by S. cosmioides reared on leaves of these three species were studied under controlled laboratory conditions. The egg-to-adult development time of S. cosmioides was shortest when reared on castor bean leaves and longest when reared on tung oil tree leaves. Larvae reared on castor bean and Barbados nut leaves had seven instars, whereas those reared on tung oil tree leaves had eight. Females originating from larvae reared on castor bean and Barbados nut leaves showed greater fecundity than did females originating from larvae reared on tung oil tree leaves. Insects fed on castor bean leaves had shorter life spans than those fed on tung oil tree and Barbados nut leaves although the oviposition period did not differ significantly. The intrinsic and finite rates of increase were highest for females reared on castor bean leaves. Total leaf consumption was highest for larvae reared on tung oil tree leaves and lowest for those reared on Barbados nut leaves. We conclude that castor bean is a more appropriate host plant for the development of S. cosmioides than are Barbados nut and tung oil tree.     

Comparative protective strategies of Cistus albidus and Quercus ilex facing photoinhibitory winter conditions

The role of structural photoprotection under photoinhibitory winter conditions was evaluated in two Mediterranean woody species: Cistus albidus (semideciduous) and Quercus ilex (evergreen). Shoots were manipulated in order to modify the light load naturally received by the leaves throughout the cold season, and monitored for changes in maximum photochemical efficiency of PSII, phenology, and leaf morphology. Naturally steep leaves of C. albidus were restrained to a horizontal position, and compared with control leaves (naturally horizontal, or steeply inclined). Fully exposed leaves of Q. ilex were artificially protected through partial shading, and compared with control leaves (not shaded). During the cold season, the most exposed (either naturally or artificially) leaves were always more photoinhibited (had lower maximal photochemical efficiency of PSII) than the photoprotected ones. The differences disappeared at the beginning of spring. Winter photoinhibition was not more pronounced in older than in younger leaves of C. albidus, indicating that inclination rather than age affected their photochemical efficiency. Leaf chlorophyll contents were not significantly affected by the manipulations. Leaf thickness decreased slightly in the least exposed shoots of the evergreen species, but no changes were detected in leaf morphological traits of the semideciduous one. The increased photoinhibitory pressure led only to slight and non-significant changes in phenology and growth.     

Variation in utilization of young leaves by a swallowtail butterfly across a deer density gradient

Phytophagous insects can be affected by plant trait-mediated indirect effects of large herbivores, but little is known regarding how these effects change in response to different densities of large herbivores. To assess the response of an insect to plant qualitative change, the response of a woody vine (Aristolochia kaempferi) to browsing by sika deer (Cervus nippon) and utilization of young leaves by a swallowtail butterfly (Byasa alcinous) were investigated across a deer density gradient. Natural and simulated deer browsing stimulated the regrowth of A. kaempferi and improved nutritional and physical quality of leaves. Young leaves were frequently observed in areas with high deer densities. The proportion of young leaves among the leaves selected for oviposition was higher than their proportion of the total number of leaves. In areas with low deer densities, the utilization of young leaves by B. alcinous increased linearly with deer density, whereas in areas with high deer densities, the utilization of young leaves was around 90%.     

Changes in the chlorophylls and carotenoids of leaves of Nicotiana tabacum during senescence

In addition to chlorophylls a and b, β-carotene, lutein, violaxanthin and neoxanthin, leaves of tobacco (Nicotiana tabacum L. cv. Virginia Gold) contain antheraxanthin in some harvests. In lower leaves, chlorophylls decreased more rapidly than carotenoids during senescence, but both types of pigment decreased at equal rates in upper leaves. The chlorophyll a:b ratio decreased only in post-mature leaves. Total carotenoid decreased with age, with the relative proportion of β-carotene increasing in lower leaves. Seasonal influences rather than age of leaf determines whether antheraxanthin is present. No esterified xanthophylls were found in senescent leaves.     

Life-history strategies affect aphid preference for yellowing leaves

According to the nutrient-translocation hypothesis, yellowing tree leaves are colonized by aphids at the end of the growing season owing to improved availability of nutrients in the phloem sap after chlorophyll degradation. We measured aphid densities on potted Betula pendula seedlings in a field site where a small proportion of foliage rapidly turned yellow before normal autumn coloration as a consequence of root anoxia. The number of adults and nymphs of the birch-feeding specialist aphids Euceraphis betulae, Betulaphis brevipilosa and Callipterinella tuberculata were counted from leaves on each of the 222 plants. Aphids were detected on 19 per cent of green leaves and on 41 per cent of yellow leaves. There was no indication of aphid avoidance of yellow leaves, and the number of winged (alate) viviparous E. betulae adults and their nymphs were significantly higher on yellow leaves than on green leaves, while the numbers of apterous B. brevipilosa and C. tuberculata did not differ between the leaf colour types. Our result suggests that only aphid species with alate generation during colour change can take advantage of yellowing leaves. This may explain the exceptional abundance of E. betulae compared with other aphid species on birches.     

Repartition des flavonols dans l'epaisseur des feuilles de quelques vegetaux vasculaires

The tissue localisation of flavonoids has been studied in leaves of Betula, Corylus, Fagus, Fraxinus, Pisum, Platanus, Quercus, Spinacia and Tilia and scales of onion bulbs. All these species contain flavonols which are, for the most part, located in the upper epidermis of the leaves. In the onion bulb, flavonols are exclusively in the epidermis. The flavonols are glycosylated and dissolved in the vacuoles. The leaves were fractionated by an original technique of abrasion of the frozen material. The physiological significance of such a distribution of flavonoids in the adult leaves or scales is discussed.     

角倍蚜虫瘿对盐肤木光合特性和总氮含量的影响

通过温室栽培和接种实验,以接种角倍蚜形成虫瘿的盐肤木和未接种角倍蚜的盐肤木为实验材料,测定和分析虫瘿对盐肤木光合特性和不同组织氮含量的影响。结果表明虫瘿对盐肤木的光合作用形成扰动,与对照植株相比较：(1)有虫瘿复叶的最大净光合速率升高,其中虫瘿初期、中期和后期分别升高14.49%、32.17%和42.01%;虫瘿还引起无虫瘿复叶最大净光合速率升高,但中期以后下降到正常水平;(2)虫瘿中期有虫瘿复叶的光饱和点升高、无虫瘿复叶光饱合点下降;虫瘿初期和中期有虫瘿复叶的光补偿点升高、无虫瘿复叶光补偿点下降;(3)虫瘿初期引起有虫瘿复叶及邻近无虫瘿复叶暗呼吸速率升高,但中期和后期影响不显著。虫瘿对盐肤木光合作用的扰动程度与小叶的位置和虫瘿生长时期密切相关。同时,虫瘿改变了盐肤木叶片氮含量分布,其中虫瘿外壁、有虫瘿复叶和无虫瘿复叶的氮含量分别为1.13%、1.98%和2.14%,这可能是营养物质从无虫瘿复叶流向有虫瘿复叶,并最终流向虫瘿,满足虫瘿和瘿内蚜虫生长需求的原因。     

Effect of Host Plant on the Infectivity of Sl MNPV to Spodoptera litura (Fabricius) (Lepidoptera: Noctuidae) Larvae

The susceptibility of Spodoptera litura to SlMNPV infection was markedly affected by phyto-chemicals ingested during the acquisition of viral inoculum on foliage of tomato and cauliflower. The LD₅₀ values computed for second, third and fourth instar larvae assayed on tomato leaves were 254, 819 and 23395 PIBs/larva, respectively whereas, it was 326, 1719 and 43843 PIBs/larva for respective instars when assayed on cauliflower leaves. Thus LD₅₀ values for second, third and fourth instar larvae were 1.28-, 2.09- and 1.87- fold lower, respectively in tomato leaves. Similarly, LT₅₀ values for second, third and fourth instar larvae assayed on tomato leaves were 7.1 and 7.5 days, respectively at inoculum dose of 2.7×10⁴ PIBs/larva whereas, it was 7.7 and 8.0 days for respective instars when assayed on cauliflower leaves at same inoculum. This result also showed that the S. litura were more susceptible on tomato leaves in comparison to cauliflower leaves as the time required for mortality was lower in tomato leaves. The possible biochemical bases for differential level of mortality of S. litura larvae on tomato and cauliflower crops needs to be investigated.     

Characterisation of the effects of leaf galls of Clusiamyia nitida (Cecidomyiidae) on Clusia lanceolata Cambess. (Clusiaceae): Anatomical aspects and chemical analysis of essential oil

Galls develop in different plant organs and are induced by the activity of various organisms. Some studies have investigated the ecological interactions between species of Clusia and gall-inducing insects. The goal of our study is to characterise changes in leaf anatomy caused by the activity of gall insects in Clusia lanceolata. Additionally, we also investigated the chemical composition of volatile compounds of normal leaves and those with galls to detect possible effects on the host plants. For anatomical studies, we used botanical material fixed in FAA₅₀. Transversal sections of the leaf blade were obtained from samples of leaves located on the third and fourth nodes from both male and female individuals. Material was studied from both sexes both with unaffected leaves and leaves containing galls. Fresh leaves of C. lanceolata were used for the extraction of volatile compounds, which were submitted to stem distillation using a modified Clevenger apparatus determining the oil yields subsequently (w/w). The unaffected leaves of female and male individuals of C. lanceolata exhibit similar anatomical structures. However, galls on leaves of both sexes show anatomical differences. The activity of the gall insect Clusiamyia nitida induces several changes in the foliar anatomy and the distribution of metabolic compounds in new tissues during gall development. However, the larvae are not able to induce significant changes in the volatile compounds of inflected leaves from male and female individuals.