Leaf light

A leaf captures light energy and transforms it through the process of photosynthesis. This glass leaf-like form also, in a sense, captures light and transforms it as it bends and refracts the rays, containing it in the deep dimensional reservoirs of the piece.

Colonial museology and the Buddhist chronicles of Sri Lanka: agency and negotiation in the development of the palm-leaf manuscript collection at the Colombo Museum

The roles of colonial museums in South Asia have been understood in terms of the dissemination of museology within the British Empire. This has often underplayed the participation of local intellectuals in the formation of museum collections, and thus has not recognized their agency in the creation of knowledge and of longstanding cultural assets. This article addresses this in part through an historical case study of the development of the palm-leaf manuscript collection at the Colombo Museum in nineteenth century Ceylon. The article focuses on the relationships between Government aims, local intellectuals and the Buddhist clergy. I argue that colonial museology and collecting activity in Ceylon ought to be understood as a negotiated process and a number of reasons for this are discussed. This article contributes to an area of museological research that is exploring the roles of indigenous actors in colonial collecting and museum practice in South Asia and broader geographical contexts.

A review of the conservation ecology of round-leaf Pomaderris Pomaderris vacciniifolia F. Muell. ex Reissek (Rhamnaceae)

Round-leaf Pomaderris Pomaderris vacciniifolia F. Muell. ex Reissek (Rhamnaceae) is a Victorian endemic shrub listed as threatened under the Flora and Fauna Guarantee Act 1988 and critically endangeredunder the Environment Protection and Biodiversity Conservation Act 1999. A review of the available literature for P. vacciniifolia indicated most information is anecdotal or found in unpublished works. Better understanding of the ecology of P. vacciniifolia may help explain why it is vulnerable, and enhance future management. Future research should focus towards better understanding of P. vacciniifolia habitat, reproductive ecology, seed dispersal mechanisms and competitive ability and how these compare with more common sympatric congeners, to determine whether any differences could explain the relative success of these species. Targeted searches for this species on public and private land are warranted to reveal additional populations and fully appreciate the distribution of this species. (The Victorian Naturalist 131 (2) 2014, 44-51).

Confocal laser scanning microscopy elucidation of the micromorphology of the leaf cuticle and analysis of its chemical composition

Electron microscopy techniques such as transmission electron microscopy (TEM) and scanning electron microscopy (SEM) have been invaluable tools for the study of the micromorphology of plant cuticles. However, for electron microscopy, the preparation techniques required may invariably introduce artefacts in cuticle preservation. Further, there are a limited number of methods available for quantifying the image data obtained through electron microscopy. Therefore, in this study, optical microscopy techniques were coupled with staining procedures and, along with SEM were used to qualitatively and quantitatively assess the ultrastructure of plant leaf cuticles. Leaf cryosections of Triticum aestivum (wheat), Zea mays (maize), and Lupinus angustifolius (lupin) were stained with either fat-soluble azo stain Sudan IV or fluorescent, diarylmethane Auramine O and were observed under confocal laser scanning microscope (CLSM). For all the plant species tested, the cuticle on the leaf surfaces could be clearly resolved in many cases into cuticular proper (CP), external cuticular layer (ECL), and internal cuticular layer (ICL). Novel image data analysis procedures for quantifying the epicuticular wax micromorphology were developed, and epicuticular waxes of L. angustifolius were described here for the first time. Together, application of a multifaceted approach involving the use of a range of techniques to study the plant cuticle has led to a better understanding of cuticular structure and provides new insights into leaf surface architecture.

Transcriptomics-based analysis using RNA-Seq of the coconut (Cocos nucifera) leaf in response to yellow decline phytoplasma infection

Invasive phytoplasmas wreak havoc on coconut palms worldwide, leading to high loss of income, food insecurity and extreme poverty of farmers in producing countries. Phytoplasmas as strictly biotrophic insect-transmitted bacterial pathogens instigate distinct changes in developmental processes and defence responses of the infected plants and manipulate plants to their own advantage; however, little is known about the cellular and molecular mechanisms underlying host–phytoplasma interactions. Further, phytoplasma-mediated transcriptional alterations in coconut palm genes have not yet been identified. This study evaluated the whole transcriptome profiles of naturally infected leaves of Cocos nucifera ecotype Malayan Red Dwarf in response to yellow decline phytoplasma from group 16SrXIV, using RNA-Seq technique. Transcriptomics-based analysis reported here identified genes involved in coconut innate immunity. The number of down-regulated genes in response to phytoplasma infection exceeded the number of genes up-regulated. Of the 39,873 differentially expressed unigenes, 21,860 unigenes were suppressed and 18,013 were induced following infection. Comparative analysis revealed that genes associated with defence signalling against biotic stimuli were significantly overexpressed in phytoplasma-infected leaves versus healthy coconut leaves. Genes involving cell rescue and defence, cellular transport, oxidative stress, hormone stimulus and metabolism, photosynthesis reduction, transcription and biosynthesis of secondary metabolites were differentially represented. Our transcriptome analysis unveiled a core set of genes associated with defence of coconut in response to phytoplasma attack, although several novel defence response candidate genes with unknown function have also been identified. This study constitutes valuable sequence resource for uncovering the resistance genes and/or susceptibility genes which can be used as genetic tools in disease resistance breeding.

Evolutionary history and leaf succulence as explanations for medicinal use in aloes and the global popularity of Aloe vera

BACKGROUND: Aloe vera supports a substantial global trade yet its wild origins, and explanations for its popularity over 500 related Aloe species in one of the world's largest succulent groups, have remained uncertain. We developed an explicit phylogenetic framework to explore links between the rich traditions of medicinal use and leaf succulence in aloes. RESULTS: The phylogenetic hypothesis clarifies the origins of Aloe vera to the Arabian Peninsula at the northernmost limits of the range for aloes. The genus Aloe originated in southern Africa ~16 million years ago and underwent two major radiations driven by different speciation processes, giving rise to the extraordinary diversity known today. Large, succulent leaves typical of medicinal aloes arose during the most recent diversification ~10 million years ago and are strongly correlated to the phylogeny and to the likelihood of a species being used for medicine. A significant, albeit weak, phylogenetic signal is evident in the medicinal uses of aloes, suggesting that the properties for which they are valued do not occur randomly across the branches of the phylogenetic tree. CONCLUSIONS: Phylogenetic investigation of plant use and leaf succulence among aloes has yielded new explanations for the extraordinary market dominance of Aloe vera. The industry preference for Aloe vera appears to be due to its proximity to important historic trade routes, and early introduction to trade and cultivation. Well-developed succulent leaf mesophyll tissue, an adaptive feature that likely contributed to the ecological success of the genus Aloe, is the main predictor for medicinal use among Aloe species, whereas evolutionary loss of succulence tends to be associated with losses of medicinal use. Phylogenetic analyses of plant use offer potential to understand patterns in the value of global plant diversity.

Randomized controlled study of the urinary excretion of biophenols following acute and chronic intake of olive leaf supplements

Olive leaf supplement was characterised by HPLC and administered to healthy young adults over 28 d (three tablets or equivalent liquid dose per day), or in a single bolus dose of three tablets (or liquid equivalent). Oleuropein was the major biophenol in the extracts. There are no data on the excretion of urinary end-products of the metabolism of the olive leaf biophenols. Following both chronic and acute ingestion neither oleuropein, nor its hydrolysis product, hydroxytyrosol, were detected in urine samples. However, glucuronic acid conjugates, derived from oleuropein aglycone were detected in all urine samples up to 6 h following acute ingestion. The data suggest that oleuropein is bioavailable, which is a necessary pre-condition for bioactivity.

Multiplexed detection: fast comprehensive sample analysis of tobacco leaf extracts using HPLC with AFT columns

Detector-based comprehensive screening analysis of complex samples of natural origin using High Performance Liquid Chromatography (HPLC) can be a complicated and time-consuming task. There are a number of ways multidetection characterization can be achieved; however, there are limitations associated with each technique. Active Flow Technology (AFT) in Parallel Segmented Flow (PSF) mode allows for multiplexed detection HPLC analysis within a single injection, whereas maintaining chromatographic performance and allowing the use of multiple destructive detectors to achieve a comprehensive yet efficient screening of a complex sample. In this study, a comprehensive characterization analysis of tobacco leaf extract was carried out through multiplexed detection using a PSF column for the detection of biomolecules by UV-Vis detection, DPPH• for reactive-oxygen species (ROS) detection, and mass spectrometry, the latter two detection methods being sample destructive.

Germination ecology and seed dispersal of a critically endangered plant: a case study of Pomaderris vacciniifolia (Round-leaf Pomaderris)

Change in ecosystem disturbance regimes from human land-use poses a worldwide problem for management of rare species. Two important types of disturbance influencing the persistence of species in Australian ecosystems are habitat fragmentation and fire. In this study, seed dispersal and the germination ecology of Pomaderris vacciniifolia-a critically endangered, rare endemic Australian shrub-were examined to identify likely influences of fire and fragmentation on the decline of populations. The response of seed germination to simulated effects of wildfire and canopy openings was investigated, as was the unaided dispersal capability of seeds from parent plants. A significant increase in germination rate was observed following 100°C heat treatment to seeds, while smoke and light exposure had little influence. Seed imbibition was strongly influenced by heat treatment. The findings indicate a likely positive post-fire germination response, with implications for recruitment success determined by moisture availability following fire. Unaided seed dispersal was limited, which partly explains the apparent decline of populations. Understanding disturbance requirements for threatened species, and subsequent management of landscapes for disturbance, will aid conservation of rare species throughout the world.

Effects of trunk-shaker harvester and ethephon on plant water status, leaf gas exchange, and yield of citrus cultivated under Mediterranean conditions

This work was aimed to study whether the application of ethephon as an abscission agent and mechanical harvest using a trunk shaker have any effect on plant water status, leaf gas exchange, and yield of mandarin and orange trees cultivated under Mediterranean conditions. The experiment was performed from 2008 to 2011 in five commercial orchards where parameters related to the plant water status and leaf gas exchange were measured before the application of ethephon, at harvest time and at different occasions after harvest. In addition, the effects of ethephon dose on yield in the current and subsequent seasons were also evaluated. Results showed that ethephon applications and mechanical harvest did not detrimentally affect plant water status in any of the cultivars studied. Furthermore, either had no effect or had a short temporal decrease effect on leaf gas exchange depending on the cultivar studied although with no consequences for the fruit yield obtained during the current season. Increasing ethephon doses led to fruit yield reductions in the mandarin ‘Orogrande’ trees in subsequent seasons. When trunk-shaker and ethephon applications were combined, however, yields from the late-maturing orange significantly decline in subsequent seasons. Overall, results show that using a trunk shaker is a viable technique to mechanically harvest citrus trees destined to both fresh and industry market and can be considered as an alternative to the traditional manual harvest usually performed under Mediterranean conditions. However, its use cannot be recommended for late-maturing oranges, such as the ‘Navel Lane Late’ in which mature fruit and fruitlets coexist in the tree at the time of harvest.

Evaluating the usefulness of continuous leaf turgor pressure measurements for the assessment of Persimmon tree water status

Continuous plant water status monitoring is crucial in order to improve irrigation management. The noninvasive Yara ZIM-probe was assessed for detecting plant water stress in Persimmon trees (Diospyros kaki L.f.). The probe measures the pressure transfer function (Pp) through a patch of an intact leaf, which is inversely correlated with the turgor pressure. This technology was evaluated in two parallel experiments involving either distinct watering regimes or rootstocks with different drought tolerance [Diospyros lotus (L) and Diospyros virginiana (V)]. Concomitant measurements of midday stem water potential (Ψstem) and trunk diameter variations were taken throughout the experiments. Pp was highly correlated with Ψstem. Persimmon leaves exhibited the inversed Pp curve phenomena under water stress, which enabled the association of a particular range of Ψstem to each of the three leaf turgor states defined. Persimmon trees with no sign of initial or total inversion ensured Ψstem above −0.8 MPa, values considered of a well-watered Persimmon tree. Yara ZIM-probe readings as well as Ψstem and trunk diameter variation measurements pointed L as a more sensitive rootstock to drought than V. In conclusion, results showed that the Yara ZIM-probe can be used to continuously monitor water status in Persimmon trees although further research would be needed to ensure their feasibility for scheduling irrigation.