Comparative ecophysiology of Graptophyllum species in Australia

Ecophysiological attributes could be causes for rarity in plants. We tested the hypothesis that a species ability to regulate photosynthesis and growth in response to environmental factors is indicative of its environmental resilience and that this is linked to its conservation status. In this study, the ecophysiology of Graptophyllum reticulatum, an Australian endangered endemic species, was compared with that of its three closely related and more common congeners G. ilicifolium, G. excelsum and G. spinigerum. Ecophysiological attributes were measured on the four species in their natural habitats and under artificially imposed environmental stresses, including changed soil conditions, excess light and low water availability, in a glasshouse experiment. Photosynthesis was determined at the photosystem II and leaf level using chlorophyll a fluorescence and gas exchange techniques. Applied to the chlorophyll fluorescence transient of leaves, the JIP test provides a Performance Index which quantifies the main steps in PSII photochemistry including light energy absorption, excitation energy trapping, and conversion of excitation energy into electron flow. At the leaf level, gas exchange measurements allow determination of maximum CO2 assimilation rates, intercellular CO2 concentrations, stomatal conductance for water vapour and instantaneous water use efficiency. Growth analysis was performed to assess relative growth rates and physiological and morphological responses. Analysis of physiological differences and responses indicated that, compared to its more common relatives, the endangered G. reticulatum was an intrinsically slow growing species, exhibited the lowest fitness when growing in favorable environments and was most sensitive to excess light stress. Photoinhibition is therefore likely to restrict the endangered species to shade habitats. Compared with the endangered G. reticulatum, the vulnerable G. ilicifolium and common G. spinigerum species were better adapted to high light and changed nutrient levels, but were more susceptible to water stress. The rare G. excelsum had the fastest growth rate and the highest fitness in favorable environments. Based on the ecophysiological attributes examined here, it is proposed that excess light is likely to be the most critical abiotic factor restricting distribution of the endangered species in a fragmented landscape. The survival of the species may be most dependent on the intactness of the habitat over-storey. In contrast, the vulnerable G. ilicifolium showed strong susceptibility to water limitation, and survival might be threatened if climate change alters habitat water relations to cause, for example, more pronounced dry periods. The rare G. excelsum which had highest carbon gain and growth in the experiments carried out in this study, may become the most successful adaptation out of the rainforest environment due to its tolerance to higher light and limited water availability. To examine the generality of the link between rarity and ecophysiology with Graptophyllum species, two dipterocarp species, narrowly endemic Dipterocarpus condorensis and local common Shorea roxburghii that are actually co-located in South-eastern Vietnam were studied. Findings in this case study confirmed the usefulness of the comparative approach based on physiological measurements, either in situ or ex situ, to explain plant rarity. The results of this study indicate ecophysiological research is a tool for examining causes of rarity and possible abiotic threats. The information gained allows assessment of environmental resilience of species and contributes essential knowledge for management and conservation of threatened plants. Such knowledge is also useful for ex situ conservation including propagation, translocation and re-introduction in restoration programs

Communication in a changing world. Increasing the impacts and benefits of scientific research activities.

The overall goal is to professionalize and strengthen the disseminating and communicating elements of protected areas in Vietnam in order to increase the impacts of projects, and to establish a set of “best practise” recommendations/manual that can be common protected areas. A workshop and a training course has been conducted, and the manual is planned to be completed and tested late 2013.publishedVersio

Effect of Planting Time on Growth and Corm Yield of Chinese Water Chestnut (Eleocharis dulcis) in the Mekong Delta, Vietnam

Experiments were conducted to study the effect of time of planting on the performance of Chinese water chestnut in the Mekong Delta in Vietnam over a single investigation. Plants of a local clone were planted in early January, March, May, July, September, or November and grown for four months. During the experiments, the photoperiod ranged from 11.2 to 12.6 h. The average daily mean temperature across the different cropping periods ranged from 27.70C to 29.10C. Information was collected on chlorophyll fluorescence, plant growth, and yield. Chlorophyll fluorescence (Fv/Fm) was greater than 0.7 in all the treatments (non-stressed), except for the first time of planting and at the end of growing. Corm yield was higher with a planting in May (525 g/plant), November (440 g/plant), and March (325 g/plant), intermediate with a planting in July (196 g/plant), and lower with a planting in January (116 g/plant) and September (55 g/plant). There were strong correlations between yield and the number of stems/plant (r = 0.84), and between yield and stem weight (r = 0.84). These results indicate that acceptable commercial yields can be achieved with water chestnut planted in May in this area

Effect of Planting Time on Growth and Corm Yield of Chinese Water Chestnut (Eleocharis dulcis) in the Mekong Delta, Vietnam

Experiments were conducted to study the effect of time of planting on the performance of Chinese water chestnut in the Mekong Delta in Vietnam over a single investigation. Plants of a local clone were planted in early January, March, May, July, September, or November and grown for four months. During the experiments, the photoperiod ranged from 11.2 to 12.6 h. The average daily mean temperature across the different cropping periods ranged from 27.70C to 29.10C. Information was collected on chlorophyll fluorescence, plant growth, and yield. Chlorophyll fluorescence (Fv/Fm) was greater than 0.7 in all the treatments (non-stressed), except for the first time of planting and at the end of growing. Corm yield was higher with a planting in May (525 g/plant), November (440 g/plant), and March (325 g/plant), intermediate with a planting in July (196 g/plant), and lower with a planting in January (116 g/plant) and September (55 g/plant). There were strong correlations between yield and the number of stems/plant (r = 0.84), and between yield and stem weight (r = 0.84). These results indicate that acceptable commercial yields can be achieved with water chestnut planted in May in this area

Metabolites as convergent trait linkages between bryophytes and tracheophytes

Trabajo presentado en el International Conference on Integrative Plant Physiology, celebrado en Sitges (España), del 27 al 29 de octubre de 201

The OJIP fast fluorescence rise characterizes Graptophyllum species and their stress responses

Causes for rarity in plants are poorly understood. Graptophyllum reticulatum is an endangered endemic species, and it has three close relatives with different conservation status: the vulnerable G. ilicifolium, the rare G. excelsum, and the common G. spinigerum. Applied to the chlorophyll a fluorescence transient of leaves, the JIP test provides a Performance Index (PI) which quantifies the main steps in photosystem II (PSII) photochemistry including light energy absorption, excitation energy trapping, and conversion of excitation energy into electron flow. The PI is calculated from three components which depend on the reaction center density, the trapping efficiency, and the electron transport efficiency. PI was measured in the natural habitats of the four species and under artificially imposed environmental stresses in the glasshouse to determine whether conservation status was related to stress resilience. The results showed that soil type is unlikely to restrict the endangered G. reticulatum, vulnerable G. ilicifolium, or rare G. excelsum because PI was similar in plants grown in diverse soils in the glasshouse. Photoinhibition is likely to restrict the endangered G. reticulatum to shade habitats because PI was significantly reduced when plants were exposed to more than 15% ambient light in controlled experiments. Water availability may determine the location and distribution of the vulnerable G. ilicifolium and common G. spinigerum because PI was reduced more than 60% when plants were exposed to water stress. While the characteristics of their natural habitats correspond to and explain the physiological responses, there was no obvious relationship between conservation status and environmental resilience. PI can be used to monitor vigor and health of populations of plants in the natural habitat. In cultivation experiments PI responds to key environmental variables that affect the distribution of species with conservation significance