Shoot tip culture and cryopreservation for eradication of Apple stem pitting virus (ASPV) and Apple stem grooving virus (ASGV) from apple rootstocks ‘M9’ and ‘M26’

This study attempted to eradicate Apple stem pitting virus (ASPV) and Apple stem grooving virus (ASGV) from virus‐infected in vitro shoots of apple rootstocks ‘M9’ and ‘M26’ using shoot tip culture and cryopreservation. In shoot tip culture, shoot tips (0.2 mm in length) containing two leaf primordia failed to show shoot regrowth. Although shoot regrowth rate was the highest in the largest shoot tips (1.0 mm in length) containing four leaf primordia, none of the regenerated shoots was virus‐free. Shoot tips (0.5 mm in length) containing two and three leaf primordia produced 100% and 10% of ASPV‐free shoots, respectively, while those (1.0 mm) containing four leaf primordia were not able to eradicate ASPV. ASGV could not be eradicated by shoot tip culture, regardless of the size of the shoot tips tested. In cryopreservation, shoot tips (0.5 mm in length) containing two leaf primordia did not resume shoot growth. Although 1.0‐mm and 1.5‐mm shoot tips gave similarly high ASPV‐free frequencies, the latter had much higher shoot regrowth rate than the former. Very similar results of shoot regrowth and virus eradication by shoot tip culture and cryopreservation were observed in both ‘M9’ and ‘M26’. Histological observations showed that only cells in upper part of apical dome and in leaf primordia 1–3 survived, while other cells were damaged or killed, in shoot tips following cryopreservation. Virus immunolocalization found ASPV was not detected in upper part of apical dome and leaf primordia 1 and 2, but was present in lower part of apical dome, and in leaf primordium 4 and more developed tissues in all samples tested. ASPV was also detected in leaf primordium 3 in about 16.7% and 13.3% samples tested in ‘M9’ and ‘M26’. ASGV was observed in apical dome and leaf primordia 1–6, leaving only a few top layers of cells in apical dome free of the virus. Different abilities of ASPV and ASGV to invade leaf petioles and shoot tips were also noted.     

Chrysanthemum expressing a linalool synthase gene ‘smells good’, but ‘tastes bad’ to western flower thrips

Herbivore‐induced plant volatiles are often involved in direct and indirect plant defence against herbivores. Linalool is a common floral scent and found to be released from leaves by many plants after herbivore attack. In this study, a linalool/nerolidol synthase, FaNES1, was overexpressed in the plastids of chrysanthemum plants (Chrysanthemum morifolium). The volatiles of FaNES1 chrysanthemum leaves were strongly dominated by linalool, but they also emitted small amount of the C11‐homoterpene, (3E)‐4,8‐dimethyl‐1,3,7‐nonatriene, a derivative of nerolidol. Four nonvolatile linalool glycosides in methanolic extracts were found to be significantly increased in the leaves of FaNES1 plants compared to wild‐type plants. They were putatively identified by LC‐MS‐MS as two linalool–malonyl–hexoses, a linalool–pentose–hexose and a glycoside of hydroxy–linalool. A leaf‐disc dual‐choice assay with western flower thrips (WFT, Frankliniella occidentalis) showed, initially during the first 15 min of WFT release, that FaNES1 plants were significantly preferred. This gradually reversed into significant preference for the control, however, at 20–28 h after WFT release. The initial preference was shown to be based on the linalool odour of FaNES1 plants by olfactory dual‐choice assays using paper discs emitting pure linalool at similar rates as leaf discs. The reversal of preference into deterrence could be explained by the initial nonvolatile composition of the FaNES1 plants, as methanolic extracts were less preferred by WFT. Considering the common occurrence of linalool and its glycosides in plant tissues, it suggests that plants may balance attractive fragrance with ‘poor taste’ using the same precursor compound.     

‘Real time’ genetic manipulation: a new tool for ecological field studies

Field experiments with transgenic plants often reveal the functional significance of genetic traits that are important for the performance of the plants in their natural environments. Until now, only constitutive overexpression, ectopic expression and gene silencing methods have been used to analyze gene‐related phenotypes in natural habitats. These methods do not allow sufficient control over gene expression for the study of ecological interactions in real time, of genetic traits that play essential roles in development, or of dose‐dependent effects. We applied the sensitive dexamethasone (DEX)‐inducible pOp6/LhGR expression system to the ecological model plant Nicotiana attenuata and established a lanolin‐based DEX application method to facilitate ectopic gene expression and RNA interference‐mediated gene silencing in the field and under challenging conditions (e.g. high temperature, wind and UV radiation). Fully established field‐grown plants were used to silence phytoene desaturase and thereby cause photobleaching only in specific plant sectors, and to activate expression of the cytokinin (CK) biosynthesis gene isopentenyl transferase (ipt). We used ipt expression to analyze the role of CKs in both the glasshouse and the field to understand resistance to the native herbivore Tupiocoris notatus, which attacks plants at small spatial scales. By spatially restricting ipt expression and elevating CK levels in single leaves, damage by T. notatus increased, demonstrating the role of CKs in this plant–herbivore interaction at a small scale. As the arena of most ecological interactions is highly constrained in time and space, these tools will advance the genetic analysis of dynamic traits that matter for plant performance in nature.     

The AAT1 locus is critical for the biosynthesis of esters contributing to ‘ripe apple’ flavour in ‘Royal Gala’ and ‘Granny Smith’ apples

The ‘fruity’ attributes of ripe apples (Malus × domestica) arise from our perception of a combination of volatile ester compounds. Phenotypic variability in ester production was investigated using a segregating population from a ‘Royal Gala’ (RG; high ester production) × ‘Granny Smith’ (GS; low ester production) cross, as well as in transgenic RG plants in which expression of the alcohol acyl transferase 1 (AAT1) gene was reduced. In the RG × GS population, 46 quantitative trait loci (QTLs) for the production of esters and alcohols were identified on 15 linkage groups (LGs). The major QTL for 35 individual compounds was positioned on LG2 and co‐located with AAT1. Multiple AAT1 gene variants were identified in RG and GS, but only two (AAT1‐RGa and AAT1‐GSa) were functional. AAT1‐RGa and AAT1‐GSa were both highly expressed in the cortex and skin of ripe fruit, but AAT1 protein was observed mainly in the skin. Transgenic RG specifically reduced in AAT1 expression showed reduced levels of most key esters in ripe fruit. Differences in the ripe fruit aroma could be perceived by sensory analysis. The transgenic lines also showed altered ratios of biosynthetic precursor alcohols and aldehydes, and expression of a number of ester biosynthetic genes increased, presumably in response to the increased substrate pool. These results indicate that the AAT1 locus is critical for the biosynthesis of esters contributing to a ‘ripe apple’ flavour.     

Monoterpene ‘thermometer’ of tropical forest‐atmosphere response to climate warming

Tropical forests absorb large amounts of atmospheric CO₂ through photosynthesis but elevated temperatures suppress this absorption and promote monoterpene emissions. Using ¹³CO₂ labeling, here we show that monoterpene emissions from tropical leaves derive from recent photosynthesis and demonstrate distinct temperature optima for five groups (Groups 1–5), potentially corresponding to different enzymatic temperature‐dependent reaction mechanisms within β‐ocimene synthases. As diurnal and seasonal leaf temperatures increased during the Amazonian 2015 El Niño event, leaf and landscape monoterpene emissions showed strong linear enrichments of β‐ocimenes (+4.4% °C^?1) at the expense of other monoterpene isomers. The observed inverse temperature response of α‐pinene (?0.8% °C^?1), typically assumed to be the dominant monoterpene with moderate reactivity, was not accurately simulated by current global emission models. Given that β‐ocimenes are highly reactive with respect to both atmospheric and biological oxidants, the results suggest that highly reactive β‐ocimenes may play important roles in the thermotolerance of photosynthesis by functioning as effective antioxidants within plants and as efficient atmospheric precursors of secondary organic aerosols. Thus, monoterpene composition may represent a new sensitive ‘thermometer’ of leaf oxidative stress and atmospheric reactivity, and therefore a new tool in future studies of warming impacts on tropical biosphere‐atmosphere carbon‐cycle feedbacks.     

Turning over a new ‘leaf’: multiple functional significances of leaves versus phyllodes in Hawaiian Acacia koa

Hawaiian endemic tree Acacia koa is a model for heteroblasty with bipinnately compound leaves and phyllodes. Previous studies suggested three hypotheses for their functional differentiation: an advantage of leaves for early growth or shade tolerance, and an advantage of phyllodes for drought tolerance. We tested the ability of these hypotheses to explain differences between leaf types for potted plants in 104 physiological and morphological traits, including gas exchange, structure and composition, hydraulic conductance, and responses to varying light, intercellular CO₂, vapour pressure deficit (VPD) and drought. Leaf types were similar in numerous traits including stomatal pore area per leaf area, leaf area‐based gas exchange rates and cuticular conductance. Each hypothesis was directly supported by key differences in function. Leaves had higher mass‐based gas exchange rates, while the water storage tissue in phyllodes contributed to greater capacitance per area; phyllodes also showed stronger stomatal closure at high VPD, and higher maximum hydraulic conductance per area, with stronger decline during desiccation and recovery with rehydration. While no single hypothesis completely explained the differences between leaf types, together the three hypotheses explained 91% of differences. These findings indicate that the heteroblasty confers multiple benefits, realized across different developmental stages and environmental contexts.     

Essential‐Oil Polymorphism in the ‘Resurrection Plant’ Myrothamnus moschatus and Associated Ethnobotanical Knowledge

Gas chromatography/mass spectroscopy analysis (GC/MS) of essential oils obtained from populations of the resurrection plant Myrothamnus moschatus, growing in different areas of Madagascar, allowed identification of three main chemotypes in the species. The first one was provided by plants with a high content of trans‐pinocarveol and pinocarvone; the second one involved plants with high percentages of limonene, cis‐ and trans‐p‐mentha‐1(7),8‐dien‐2‐ol, and β‐selinene; and the third chemotype was characterized by plants with high levels of oxygenated sesquiterpenes such as caryophyllene oxide and α‐ and β‐isomers of caryophylla‐4(12),8(13)‐dien‐5‐ol. Chemical data were supported by chemometric technique as the principal component analysis. Furthermore, the relationship between the dioecy and phytochemistry within one population was also considered. Finally, correlations between chemical variations and ethnobotanical data were assessed.     

Molecular Identification and Diversity of ‘Candidatus Phytoplasma solani’ Associated with Red‐leaf Disease of Salvia miltiorrhiza in China

Reddening disease has recently been threatening Salvia miltiorrhiza in China, ranging from 30 to 50%. The main symptoms observed, such as plant stunting, inflorescence malformation, leaf reddening, fibrous roots browning, skin blackening and eventually root rot, are typically associated with phytoplasma infection. The presence of phytoplasmas was demonstrated through phytoplasma‐specific PCR, with the expected amplification (1.8 kb) from symptomatic S. miltiorrhiza plants from Shangluo, Shangzhou and Luonan fields in Shaanxi Province of China. The sequences of 16S rRNA, tuf, secY and vmp1 genes amplified from LN‐1 phytoplasma shared the closest homologies of 99%, 100%, 99% and 98% with those of the reference strain Candidatus Phytoplasma solani (subgroup 16SrXII‐A), respectively. The phylogenetic trees showed that LN‐1 phytoplasma clustered with the members of 16SrXII‐A group, including Ca. P. solani. Computer‐simulated restriction fragment length polymorphism analysis further supported this classification. Diversity analysis showed that all ‘Ca. P. solani’ strains identified from the three different regions examined shared 100% identical 16S rRNA, tuf, secY and vmp1 nucleotide sequences. To the best of our knowledge, this is the first report of phytoplasma infecting the medicinal plant of S. miltiorrhiza. The results demonstrate that ‘Ca. P. solani’ is the presumptive aetiological agent of S. miltiorrhiza reddening disease in China.     

Mixed Infection and Natural Spread of ‘Candidatus Phytoplasma asteris’ and Mungbean Yellow Mosaic India Virus Affecting Soya Bean Crop in India

Suspected phytoplasma and virus‐like symptoms of little leaf, yellow mosaic and witches’ broom were recorded on soya bean and two weed species (Digitaria sanguinalis and Parthenium hysterophorus), at experimental fields of Indian Agricultural Research Institute, New Delhi, India, in August–September 2013. The phytoplasma aetiology was confirmed in symptomatic soya bean and both the weed species by direct and nested PCR assays with phytoplasma‐specific universal primer pairs (P1/P6 and R16F2n/R16R2n). One major leafhopper species viz. Empoasca motti Pruthi feeding on symptomatic soya bean plants was also found phytoplasma positive in nested PCR assays. Sequencing BLASTn search analysis and phylogenetic analysis revealed that 16Sr DNA sequences of phytoplasma isolates of soya bean, weeds and leafhoppers had 99% sequence identity among themselves and were related to strains of ‘Candidatus Phytoplasma asteris’. PCR assays with Mungbean yellow mosaic India virus (MYMIV) coat‐protein‐specific primers yielded an amplicon of approximately 770 bp both from symptomatic soya bean and from whiteflies (Bemisia tabaci) feeding on soya bean, confirmed the presence of MYMIV in soya bean and whitefly. Hence, this study suggested the mixed infection of MYMIV and ‘Ca. P. asteris’ with soya bean yellow leaf and witches’ broom syndrome. The two weed species (D. sanguinalis and P. hysterophorus) were recorded as putative alternative hosts for ‘Ca. P. asteris’ soya bean Indian strain. However, the leafhopper E. motti was recorded as putative vector for the identified soya bean phytoplasma isolate, and the whitefly (B. tabaci) was identified as vector of MYMIV which belonged to Asia‐II‐1 genotype.     

Thermal limits of leaf metabolism across biomes

High‐temperature tolerance in plants is important in a warming world, with extreme heat waves predicted to increase in frequency and duration, potentially leading to lethal heating of leaves. Global patterns of high‐temperature tolerance are documented in animals, but generally not in plants, limiting our ability to assess risks associated with climate warming. To assess whether there are global patterns in high‐temperature tolerance of leaf metabolism, we quantified T_crit (high temperature where minimal chlorophyll a fluorescence rises rapidly and thus photosystem II is disrupted) and T_max (temperature where leaf respiration in darkness is maximal, beyond which respiratory function rapidly declines) in upper canopy leaves of 218 plant species spanning seven biomes. Mean site‐based T_crit values ranged from 41.5 °C in the Alaskan arctic to 50.8 °C in lowland tropical rainforests of Peruvian Amazon. For T_max, the equivalent values were 51.0 and 60.6 °C in the Arctic and Amazon, respectively. T_crit and T_max followed similar biogeographic patterns, increasing linearly (?8 °C) from polar to equatorial regions. Such increases in high‐temperature tolerance are much less than expected based on the 20 °C span in high‐temperature extremes across the globe. Moreover, with only modest high‐temperature tolerance despite high summer temperature extremes, species in mid‐latitude (~20–50°) regions have the narrowest thermal safety margins in upper canopy leaves; these regions are at the greatest risk of damage due to extreme heat‐wave events, especially under conditions when leaf temperatures are further elevated by a lack of transpirational cooling. Using predicted heat‐wave events for 2050 and accounting for possible thermal acclimation of T_crit and T_max, we also found that these safety margins could shrink in a warmer world, as rising temperatures are likely to exceed thermal tolerance limits. Thus, increasing numbers of species in many biomes may be at risk as heat‐wave events become more severe with climate change.     

The influence of epidermal windows on the light environment within the leaves of six succulents

An omni-directional fibre optic microprobe was used to measure the quantity and quality of light within the leaves of six succulents having epidermal windows, three species having a subterranean growth habit (Haworthia truncata, Lithops olivacea, and Opthalmophyllum longum) and three growing above ground (Peperomia dolabriformis, P. graveolens, and the sprawling vine Senecio rowleyanus). Although light levels at most locations inside the leaves of all species were high, near those incident on the window surfaces, light levels inside the leaves of the two species of Peperomia often greatly exceeded incident light levels, indicating considerable light scattering and focusing by the leaf tissue. The spectral quality of light inside the leaves of all taxa reflected the absorption properties of chlorophyll, with most of the photons in the green wavelengths. Light quality and quantity inside the leaves did not correlate with the growth habit of the plants, the size of the window (as a proportion of the total leaf area), or location inside the leaf, although light levels generally declined and wavelengths increased deeper in the leaves. Application of reflective tape to the windows reduced internal light levels in L. olivacea and S. rowleyanus, although reductions were not always statistically significant. Although light levels throughout the leaves of P. graveolens were substantially and significantly reduced as a result of the application of reflective tape to its windows, the light levels even at the basal chlorenchyma on the abaxial side of the leaf remained high. In all species investigated, the levels of near-infrared radiation inside the leaves were surprisingly high, yet also declined deeper inside the succulent leaves. This near-infrared radiation may add to the heat load of these plants. Furthermore, application of reflective tape to the windows also reduced the amount of near-infrared radiation inside the leaves of the three succulents examined. These results led to a novel, testable hypothesis that may help to explain previous findings that application of reflective tape to the windows of the leaves of these succulents did not effect a reduction in photosynthetic activity.     

‘Cylindrocarpon’ and Ilyonectria Species Causing Root and Crown Rot Disease of Potted Laurustinus Plants in Italy

During the 2012 and 2013 growing seasons, a disease was detected on potted laurustinus (Viburnum tinus) plants in two nurseries located in the Catania province (eastern Sicily, Italy). ‘Cylindrocarpon’‐like species were consistently recovered from crown rot and stem rot tissues. Based on morphological characteristics, DNA sequencing and phylogenetic analysis of β‐tubulin (TUB), histone H3 (HIS3) and translation elongation factor‐1α (TEF‐1 α) gene sequences, the fungi associated with symptomatic tissues were identified as ‘Cylindrocarpon’ pauciseptatum, Ilyonectria novozelandica and I. torresensis. Koch's postulates were fulfilled by pathogenicity tests carried out on potted V. tinus cuttings. To our knowledge, this is the first report worldwide of ‘C.’ pauciseptatum, I. novozelandica and I. torresensis causing disease on V. tinus.     

Moderating Night Radiative Cooling Reduces Frost Damage to Metrosideros polymorpha Seedlings Used for Forest Restoration in Hawaii

Winter frosts caused by radiative cooling were hypothesized to limit successful reintroduction of Hawaiian plants other than Acacia koa to alien‐dominated grasslands above 1700 m elevation. We determined, in the laboratory, the temperature at which irreversible tissue damage occurred to Metrosideros polymorpha leaves. We also conducted a field study of this species to determine if (1) leaf damage was correlated with sub‐zero leaf temperatures, (2) radiative cooling could be moderated by canopies of A. koa, and (3) low soil temperatures contributed to seedling damage. The last was evaluated by thermally buffering seedlings with water‐filled bladders placed at their base to keep roots warm, or by installing a radiation shield to reduce early morning transpiration when water uptake from cold soils would be least. Leaf temperatures were monitored between midnight and 7:00 a.m. using fine‐wire thermocouples, and leaf damage was recorded monthly. In the laboratory, supercooling protected leaves from mild sub‐zero temperatures; irreversible tissue damage occurred at about ?8°C. In the field, leaf damage was strongly correlated with degree‐hours below freezing. Unprotected seedlings suffered the greatest leaf damage. Those sheltered under A. koa trees rarely experienced temperatures below ?3°C, and damage was minimal. Shaded and thermally buffered seedlings suffered less damage than unprotected plants, probably due to elevated leaf temperatures rather than improved water relations. Using A. koa or artificial devices to reduce radiative cooling during winter nights should enhance establishment of M. polymorpha in high‐elevation rangeland.     

A global perspective of ground level, ‘ambient’ carbon dioxide for assessing the response of plants to atmospheric CO2

For most studies involving the response of plants to future concentrations of atmospheric carbon dioxide (CO₂), a current concentration of 360–370 μatm is assumed, based on recent data obtained from the Mauna Loa observatory. In the present study, average seasonal diurnal values of ambient CO₂ obtained at ground level from three global locations (Australia, Japan and the USA) indicated that the average CO₂ (at canopy height) can vary from over 500 μatm at night to 350 μatm during the day with average 24‐h values ranging from 390 to 465 μatm. At all sites sampled, ambient CO₂ rose to a maximum value during the pre‐dawn period (03.00–06.00 hours); at sunrise, CO₂ remained elevated for several hours before declining to a steady‐state concentration between 350 and 400 μatm by mid‐morning (08.00–10.00 hours). Responses of plant growth to simulations of the observed variation of in situ CO₂ were compared to growth at a constant CO₂ concentration in controlled environment chambers. Three diurnal patterns were used (constant 370 μatm CO₂, constant 370 during the day (07.00–19.00 hours), high CO₂ (500 μatm) at night; or, high CO₂ (500 μatm) at night and during the early morning (07.00–09.00 hours) decreasing to 370 μatm by 10.00 hours). Three plant species ? soybean (Glycine max, L (Merr.), velvetleaf (Abutilon theophrasti L.) and tomato (Lycopersicon esculentum L.) ? were grown in each of these environments. For soybean, high night‐time CO₂ resulted in a significant increase in net assimilation rate (NAR), plant growth, leaf area and biomass relative to a constant ambient value of CO₂ by 29 days after sowing. Significant increases in NAR for all three species, and significant increases in leaf area, growth and total biomass for two of the three C3 species tested (velvetleaf and soybean) were also observed after 29 days post sowing for the high night/early morning diurnal pattern of CO₂. Data from these experiments suggest that the ambient CO₂ concentration experienced by some plants is higher than the Mauna Loa average, and that growth of some agricultural species at in situ CO₂ levels can differ significantly from the constant CO₂ value used as a control in many CO₂ experiments. This suggests that a reassessment of control conditions used to quantify the response of plants to future, elevated CO₂ may be required.     

‘Fukusensor:’ a genetically engineered plant for reporting DNA damage in response to gamma radiation

Transgenic plants can be designed to be ‘phytosensors’ for detection of environmental contaminants and pathogens. In this study, we describe the design and testing of a radiation phytosensor in the form of green fluorescence protein (GFP)‐transgenic Arabidopsis plant utilizing a DNA repair deficiency mutant background as a host. Mutant lines of Arabidopsis AtATM (At3g48190), which are hypersensitive to gamma irradiation, were used to generate stable GFP transgenic plants in which a gfp gene was under the control of a strong constitutive CaMV 35S promoter. Mutant and nonmutant genetic background transgenic plants were treated with 0, 1, 5, 10 and 100 Gy radiation doses, respectively, using a Co‐60 source. After 1 week, the GFP expression levels were drastically reduced in young leaves of mutant background plants (treated by 10 and 100 Gy), whereas there were scant visible differences in the fluorescence of the nonmutant background plants. These early results indicate that transgenic plants could serve in a relevant sensor system to report radiation dose and the biological effects to organisms in response to radionuclide contamination.     

Impacts of a spring heat wave on canopy processes in a northern hardwood forest

Heat wave frequency, duration, and intensity are predicted to increase with global warming, but the potential impacts of short‐term high temperature events on forest functioning remain virtually unstudied. We examined canopy processes in a forest in Central Ontario following 3 days of record‐setting high temperatures (31–33 °C) that coincided with the peak in leaf expansion of dominant trees in late May 2010. Leaf area dynamics, leaf morphology, and leaf‐level gas‐exchange were compared to data from prior years of sampling (2002–2008) at the same site, focusing on Acer saccharum Marsh., the dominant tree in the region. Extensive shedding of partially expanded leaves was observed immediately following high temperature days, with A. saccharum losing ca. 25% of total leaf production but subsequently producing an unusual second flush of neoformed leaves. Both leaf losses and subsequent reflushing were highest in the upper canopy; however, retained preformed leaves and neoformed leaves showed reduced size, resulting in an overall decline in end‐of‐season leaf area index of 64% in A. saccharum, and 16% in the entire forest. Saplings showed lower leaf losses, but also a lower capacity to reflush relative to mature trees. Both surviving preformed and neoformed leaves had severely depressed photosynthetic capacity early in the summer of 2010, but largely regained photosynthetic competence by the end of the growing season. These results indicate that even short‐term heat waves can have severe impacts in northern forests, and suggest a particular vulnerability to high temperatures during the spring period of leaf expansion in temperate deciduous forests.     

Recovery from Cucumber Mosaic Virus Infection for ‘Calwonder’ Bell Pepper Plants Does not Counter Negative Impacts on Plant Growth

Cucumber mosaic virus (CMV) accumulation in leaves and stems of infected bell pepper plants at specific symptom stages was evaluated with an emphasis on the transition from full infection to recovery from Cucumber mosaic disease. Four symptom phases occurred in successive order, designated chlorosis (leaves 6–8), mosaic (leaves 9–11/12), leaf distortion (first series of leaves on secondary and tertiary branches) and recovery (progressive recovery with newly emerging leaves in tertiary and younger branches). In situ detection of CMV in leaf tissues revealed widespread occurrence in leaves expressing chlorosis and mosaic symptoms but reduced, localized occurrence in leaves in the recovery phase. Similarly, CMV accumulated to high levels throughout stems expressing chlorosis and mosaic symptoms but with dramatically reduced levels for plants in the recovery symptom phase. Stunting of internodes occurred at all locations above the inoculated leaves by the first expression of systemic symptoms, suggesting an impact on stem growth in response to initial virus invasion of young developing tissues of the stem. Despite the recovery from CMV infection, plant growth was negatively impacted early in the infection process and remained so through the course of the experiment.     

Potential defence from herbivory by ‘dazzle effects’ and ‘trickery coloration’ of leaf variegation

The very conspicuous dazzle coloration invented for naval defence during World War I was used in pre‐radar days to mislead attackers of naval units about vessel size, type, speed, and direction. Among several potential types of defences, it is proposed that zebra‐like white leaf variegation may defend leaves and other plant organs from herbivory as a result of dazzle effects. Two different dazzle effects may be involved in defending plants from herbivory, making it hard for herbivores (1) to decide where, in a three‐dimensional space, to bite the leaves (large herbivores) and (2) to land on them (insects). In addition, the related types of leaf coloration described in the present study, comprising parallels of military defensive trickery naval painting, may also deceive herbivores about the actual shape, location, and identity of leaves. Some of these visual defences may operate at the same time as other visual defences, such as aposematism, or serve various physiological functions. © 2014 The Linnean Society of London, Biological Journal of the Linnean Society, 2014, 111 , 692–697.     

Physical leaf defenses – altered by Zea life‐history evolution,domestication, and breeding – mediate oviposition preference of a specialist leafhopper

Plant anti‐herbivore defenses are known to be affected by life‐history evolution, as well as by domestication and breeding in the case of crop species. A suite of plants from the maize genus Zea (Poaceae) and the specialist herbivore Dalbulus maidis (DeLong & Wolcott) (Hemiptera: Cicadellidae) were used to test the hypothesis that anti‐herbivore defenses are affected by plant life‐history evolution and human intervention through domestication and breeding for high yield. The suite of plants included a maize (Zea mays ssp. mays L.) commercial hybrid, a maize landrace, two populations of the annual Balsas teosinte (Z. mays ssp. parviglumis Iltis & Doebley), and perennial teosinte (Z. diploperennis Iltis, Doebley & Guzman). Leaf toughness, pubescence, and oviposition preference were compared among the suite of host plants looking for effects of transitions in life history (i.e., from perennial to annual life cycle), domestication (i.e., from wild annual to domesticated annual), and breeding (i.e., from landrace to hybrid maize) on defense against D. maidis. Results on leaf toughness suggested that the life‐history and domestication transitions weakened the plant's resistance to penetration by the mouthparts and ovipositor of D. maidis, whereas results on pubescence suggested that this putative defense was strengthened with the breeding transition, contrary to expectations. Results on oviposition preference of D. maidis coincided with the expectation that life‐history and domestication transitions would lead to preference for Balsas teosinte over perennial teosinte, and of landrace maize over Balsas teosinte. Also, a negative correlation suggested that oviposition preference is significantly influenced by leaf toughness. Overall, the results suggested that Zea defenses against the specialist herbivore D. maidis were variably affected by plant life‐history evolution, domestication, and breeding, and that chemical defense may play a role in Zea defense against D. maidis because leaf toughness and pubescence only partially explained its host preferences.