Plant Physiological Conditions Research Articles

PHYSIOLOGICAL AND PRODUCTIVE PARAMETERS OF OLIVE TREES (OLEA EUROPAEA L.) UNDER DIFFERENT IRRIGATION SCHEDULING IN CENTRAL-SOUTH ITALY

Olive tree is a drought tolerant species withstanding prolonged dry periods using physiological and morphological mechanisms of resistance to water stress. In this work we measured functional and yield changes in olive plants (Olea europaea L. ‘Frantoio’ and ‘Leccino’) subjected to different irrigation scheduling. The study was carried out in field trials during the years 2006 and 2007 in a typical hilly olive growing area of southern Italy. Irrigation treatments were applied from pit hardening to fruit veraison and consisted of: a non-irrigated control, a treatment fully irrigated with 100% of maximum crop evapotranspiration (ETc) and two deficit treatments that received 33 and 66% of ETc. Physiological parameters related to plant water status and nitrogen concentration in leaves were determined regularly during the two growing seasons. Vegetative development was monitored measuring the transverse trunk cross-section area, the crown volume, and the dry mass pruned yearly. Yield parameters (dry mass and oil content) were measured on fruits having similar maturity index. Irrigation levels significantly modified plant physiological conditions and vegetative growth of the two cultivars. Significant changes in xylem water potential, stomatal conductance and leaf nitrogen concentration were observed between irrigation treatments, and changes depended on cultivar and time of measurement. Trunk cross-section area, crown volume and pruned wood increased with the amount of water applied. Fruit and oil yield per plant showed a gradual increase with the amount of water supplied to trees, reaching the highest values in plants irrigated with 100% of ETc.

Non-linear effects of drought under shade: reconciling physiological and ecological models in plant communities

The combined effects of shade and drought on plant performance and the implications for species interactions are highly debated in plant ecology. Empirical evidence for positive and negative effects of shade on the performance of plants under dry conditions supports two contrasting theoretical models about the role of shade under dry conditions: the trade-off and the facilitation hypotheses. We performed a meta-analysis of field and greenhouse studies evaluating the effects of drought at two or more irradiance levels on nine response variables describing plant physiological condition, growth, and survival. We explored differences in plant response across plant functional types, ecosystem types and methodological approaches. The data were best fit using quadratic models indicating a humped-back shape response to drought along an irradiance gradient for survival, whole plant biomass, maximum photosynthetic capacity, stomatal conductance and maximal photochemical efficiency. Drought effects were ameliorated at intermediate irradiance, becoming more severe at higher or lower light levels. This general pattern was maintained when controlling for potential variations in the strength of the drought treatment among light levels. Our quantitative meta-analysis indicates that dense shade ameliorates drought especially among drought-intolerant and shade-tolerant species. Wet tropical species showed larger negative effects of drought with increasing irradiance than semiarid and cold temperate species. Non-linear responses to irradiance were stronger under field conditions than under controlled greenhouse conditions. Non-linear responses to drought along the irradiance gradient reconciliate opposing views in plant ecology, indicating that facilitation is more likely within certain range of environmental conditions, fading under deep shade, especially for drought-tolerant species.Electronic supplementary materialThe online version of this article (doi:10.1007/s00442-011-2196-5) contains supplementary material, which is available to authorized users.

Using leaf chlorophyll to parameterize light-use-efficiency within a thermal-based carbon, water and energy exchange model

Chlorophylls absorb photosynthetically active radiation and thus function as vital pigments for photosynthesis, which makes leaf chlorophyll content (C ab) useful for monitoring vegetation productivity and an important indicator of the overall plant physiological condition. This study investigates the utility of integrating remotely sensed estimates of C ab into a thermal-based Two-Source Energy Balance (TSEB) model that estimates land-surface CO 2 and energy fluxes using an analytical, light-use-efficiency (LUE) approach to estimating bulk canopy resistance. The LUE model component computes canopy-scale carbon assimilation and transpiration fluxes, internally estimating fluctuations in effective LUE from a nominal (species-dependent) value (LUE n) in response to short-term variations in environmental conditions. LUE n, however, may vary on a daily timescale, responding to changes in plant phenology, physiological condition and nutrient status. Therefore, remote sensing methodologies for improving daily estimates of LUE n have been investigated. Day-to-day variations in LUE n were assessed for a heterogeneous corn crop field in Maryland, U.S.A. through model optimization with eddy covariance CO 2 flux tower observations. The optimized daily LUE n values were then compared to gridded estimates of C ab over the tower flux footprint, retrieved from a canopy reflectance model driven by green, red and near-infrared imagery acquired with an aircraft imaging system. The tower-calibrated LUE n data were generally well correlated with airborne retrievals of C ab, and hourly water, energy and carbon flux estimation accuracies from TSEB were significantly improved when using C ab for delineating spatio-temporal variations in LUE n. The study highlights the potential synergy between thermal infrared and shortwave reflective wavebands in producing valuable remote sensing data for estimating carbon, water and heat fluxes within a two-source energy balance framework.

Spectral indices to monitor nitrogen-driven carbon uptake in field corn

Climate change is heavily impacted by changing vegetation cover and productivity with large scale monitoring of vegetation only possible with remote sensing techniques. The goal of this effort was to evaluate existing reflectance (R) spectroscopic methods for determining vegetation parameters related to photosynthetic function and carbon (C) dynamics in plants. Since nitrogen (N) is a key constituent of photosynthetic pigments and C fixing enzymes, biological C sequestration is regulated in part by N availability. Spectral R information was obtained from field corn grown at four N application rates (0, 70, 140, 280 kg N/ha). A hierarchy of spectral observations were obtained: leaf and canopy with a spectral radiometer; aircraft with the AISA sensor; and satellite with EO-1 Hyperion. A number of spectral R indices were calculated from these hyperspectral observations and compared to geo-located biophysical measures of plant growth and physiological condition. Top performing indices included the R derivative index D730/D705 and the normalized difference of R750 vs. R705 (ND705), both of which differentiated three of the four N fertilization rates at multiple observation levels and yielded high correlations to these carbon parameters: light use efficiency (LUE); C:N ratio; and crop grain yield. These results advocate the use of hyperspectral sensors for remotely monitoring carbon cycle dynamics in managed terrestrial ecosystems.

Plant Antimicrobial Peptides: An Overview of SuperSAGE Transcriptional Profile and a Functional Review

Defensin, thionin and lipid transfer protein (LTP) gene families, which antimicrobial activity has an attractive use in protein engineering and transgenic production of agronomical important plants, have been here functionally reviewed. Also, a transcriptional overview of a set of plant SuperSAGE libraries and analysis looking for 26 bp tags possibly annotated for those families is presented. Tags differentially expressed (p = 0.05) or constitutively transcribed were identified from leaves or roots SuperSAGE libraries from important Brazilian plant species [cowpea (Vigna unguiculata (L.) Walp.), soybean (Glycine max (L.) Merr.) and modern sugarcane hybrids (Saccharum spp.)] submitted to abiotic [salt (100 mM NaCl) or drought] or biotic stresses [fungus inoculation (Phakopsora pachyrhizi; Asiatic Soyben Rust phytopathogen)]. The diverse transcriptional patterns observed, probably related to the variable range of targets and functions involved, could be the first step to unravel the antimicrobial peptide world and the plant stress response relationship. Moreover, SuperSAGE opens the opportunity to find some SNPs or even rare transcript that could be important on plant stress resistance mechanisms. Putative defensin or LTP identified by SuperSAGE following a specific plant treatment or physiological condition could be useful for future use in genetic improvement of plants.

Unravelling the regulatory mechanisms that modulate the MEP pathway in higher plants

The methyl-D-erythritol 4-phosphate pathway is responsible for the biosynthesis of a substantial number of natural compounds of biological and biotechnological importance. In recent years, this pathway has become an obvious target to develop new herbicides and antimicrobial drugs. In addition, the production of a variety of compounds of medical and agricultural interest may be possible through the genetic manipulation of this pathway. To this end, a complete understanding of the molecular mechanisms that regulate this pathway is of tremendous importance. Recent data have accumulated that show some of the multiple mechanisms that regulate the methyl-D-erythritol 4-phosphate pathway in plants. In this review we will describe some of these and discuss their implications. It has been demonstrated that 1-deoxy-D-xylulose-5-phosphate synthase (DXS), the first enzyme of this route, plays a major role in the overall regulation of the pathway. A small gene family codes for this enzyme in most of the plants which have been analysed so far, and the members of these gene families belong to different phylogenetic groups. Each of these genes exhibits a distinct expression pattern, suggesting unique functions. One of the most interesting regulatory mechanisms recently described for this pathway is the post-transcriptional regulation of the level of DXS and DXR proteins. In the case of DXS, this regulation appears conserved among plants, supporting its importance. The evidence accumulated suggests that this regulation might link the activity of this pathway with the plant's physiological conditions and the metabolic demand for the final products of this route.

The ACCENT-VOCBAS field campaign on biosphere-atmosphere interactions in a Mediterranean ecosystem of Castelporziano (Rome): site characteristics, climatic and meteorological conditions, and eco-physiology of vegetation

Abstract. Biosphere-atmosphere interactions were investigated on a sandy dune Mediterranean ecosystem in a field campaign held in 2007 within the frame of the European Projects ACCENT and VOCBAS. The campaign was carried out in the Presidential estate of Castelporziano, a peri-urban park close to Rome. Former campaigns (e.g. BEMA) performed in Castelporziano investigated the emission of biogenic volatile organic compounds (BVOC). These campaigns focused on pseudosteppe and evergreen oak groves whereas the contribution of the largely biodiverse dune vegetation, a prominent component of the Mediterranean ecosystem, was overlooked. While specific aspects of the campaign will be discussed in companion papers, the general climatic and physiological aspects are presented here, together with information regarding BVOC emission from the most common plant species of the dune ecosystem. During the campaign regular air movements were observed, dominated by moderate nocturnal land breeze and diurnal sea breeze. A regular daily increase of ozone concentration in the air was also observed, but daily peaks of ozone were lower than those measured in summer on the same site. The site was ideal as a natural photochemical reactor to observe reaction, transport and deposition processes occurring in the Mediterranean basin, since the sea-land breeze circulation allowed a strong mixing between biogenic and anthropogenic emissions and secondary pollutants. Measurements were run in May, when plant physiological conditions were optimal, in absence of severe drought and heat stress. Foliar rates of photosynthesis and transpiration were as high as generally recorded in unstressed Mediterranean sclerophyllous plants. Most of the plant species emitted high level of monoterpenes, despite measurements being made in a period in which emissions of volatile isoprenoids could be restrained by developmental and environmental factors, such as leaf age and relatively low air temperature. Emission of isoprene was generally low. Accounting for the high monoterpene spring emission of the dune ecosystem may be important to correct algorithms at regional and ecosystem levels, and to interpret measurements of fluxes of volatile isoprenoids and secondary pollutants.

Modeling of plant adaptation to climatic drought induced water deficit

AbstractSoil moisture flux to root surface is considered the main determining factor of the transpiration intensity of plants. This assumption is valid not only in optimal plant physiological conditions without any physical barrier for the evaporation from the leaves, but in climatic drought as well, when high usable soil water amount cannot supply the evapo-transpiration intensity of plant. A new algorithm we built up describing the plant adaptation in climatic drought when stoma’s closure and reduction of plant’s potential evapo-transpiration (PET) starts. The adaptation algorithm of Doorenbos et al. (1978) is developed further defining that soil moisture content initiating the stomata’s closure. The critical soil moisture content is varying according to the PET, and drought tolerance of plant. If soil moisture content is less than the critical one, the plant evapo-transpiration (ET) can be highly different in the drought tolerance plant groups. The new drought tolerance algorithm is applied to maize field plots on chernozem soil of the experimental station of the Debrecen University, in East Hungary. Simulated soil water storages are compared to measured ones of a field plot treatment in five consecutive years. The soil moisture content profiles are measured with a BR-150 capacitance probe (Andrén et al. 1991). Differences between measured and simulated soil water storages are not significant in 2003. Simulations indicate low soil water storages in autumn of 2006, and in the first half of 2007 predicting the low maize production realized in 2007. The new plant adaptation algorithm can be used for a climate and soil moisture content sensitive irrigation control as well. The maize production is an illustrative biohydrological example of water flow through the soil-plant-atmosphere continuum.

Separating physiologically and directionally induced changes in PRI using BRDF models

Monitoring of photosynthetic efficiency ( ε) over space and time is a critical component of climate change research as it is a major determinant of the amount of carbon accumulated by terrestrial ecosystems. While the past decade has seen progress in the remote estimation of ε at the leaf, canopy and stand level using the photochemical reflectance index PRI (based on the normalized difference of reflectance at 531 and 570 nm), little is known about the temporal and spatial requirements for up-scaling PRI to landscape and global levels using satellite observations. One potential way to investigate these requirements is using automated tower-based remote sensing platforms, which observe stand level reflectance with high spatial, temporal, and spectral resolution. Prediction of ε from PRI diurnally or over a full year requires observations of canopy reflectance over multiple view and sun-angles. As a result, these observations are subject to directional reflectance effects which can be interpreted in terms of the bidirectional reflectance distribution function (BRDF) using semi-empirical kernel driven models. These semi-empirical models use a combination of physically based BRDF shapes and empirical observations to standardize multi-angular observations to a common viewing and illumination geometry. Directional reflectance effects are thereby modeled as a linear superposition of mathematical kernels, representing the bi-direction variation in reflectance from isotropic, geometric, and volumetric scattering components of the vegetation canopy. However, because variations in plant physiological conditions can also introduce bidirectional reflectance variations, we introduce an approach to separate bidirectional effects arising purely from plant physiological status from other effects by stratifying PRI observations into categories based on environmental conditions for which the expected physiological variability is low. Within each of these PRI strata, the derived physically based BRDF shapes were used to standardize multi-angular PRI measurements to a common viewing and illumination geometry. The method significantly enhanced the relationship found between PRI and ε (from r 2 = 0.38 for the directionally uncorrected case to r 2 = 0.82 for the directionally corrected case) from data measured continuously over the course of 1 year over an evergreen conifer forest using an automated platform. Results show that isotropic PRI scattering is highly correlated to changes in ε, while geometric scattering can be related to canopy level shading. Instrumentation and approaches such as the one demonstrated in this study may be integrated into current efforts aiming at predicting ε at global scales using satellite observations.

Productivity of soybean-rhizobium symbiosis after modification of root nodule bacteria activity with exogenous proteins

Plant growth experiments were conducted to assess symbiotic efficiency, photosynthetic rates, and the development of soybean (Glycine max (L.) Merrill) seedlings after seed inoculation with active and inactive strains of root nodule bacteria Bradyrhizobium japonicum preincubated in the presence homologous and heterologous proteins. The properties of active and inactive symbiotic strains were differentially modulated by homologous soybean lectin, which had a marked influence on plant physiological condition. The incubation of active rhizobia with a homologous lectin, i.e., lectin of the respective plant, increased the nitrogen-fixing activity of nodules and, consequently, elevated photosynthetic rates and weight increments in soybean plants. At the same time, the homologous lectin suppressed the symbiotic properties of inactive strain of nodule bacteria. The preincubation of rhizobia with a heterologous pea lectin had virtually no effect on functioning of symbiotic apparatus and photosynthetic rate, whereas the preincubation of root nodule bacteria with human albumin exerted an effect similar to that induced by a homologous lectin on symbiotic productivity.

Suitability of stressed and vigorous plants to various insect herbivores

We conducted a controlled experiment to test the plant vigor and the plant stress hypotheses. The two hypotheses associate plant physiological conditions to insect feeding mode and performance. We exposed tomato, Lycopersicon esculentum, to different types of growing conditions: optimal (vigorous plants), resource based stress (water and/or nutrient deficit), and physical stress (punched hole in terminal leaflets). Plant performance, foliar nutritional value for insects and chemical defenses were analyzed after 14 d. These plants were offered to insects belonging to distinct feeding guilds: the silverleaf whitefly, Bemisia argentifolii, a phloem feeder; the leafminer, Liriomyza trifolii; and the corn earworm, Heliothis zea, a leaf chewing caterpillar. The experimental conditions generated a gradient of plant growth in the following order: optimal (vigorous)>control=hole punched>no fertilizer>no water>no water and no fertilizer. The last two treatments resulted in plants with poor nutritional value (based on %water, C/N, %N) and higher levels of defensive compounds (i.e., peroxidase and total phenolics) compared with control and the vigorous plants. Hole‐punching neither affected plant growth nor any of the phytochemicals measured. In a choice experiment adult whitefly ovipositioning was not affected by either vigor or punching but was reduced on the other plants (P<0.01). Leafminer feeding and oviposition and corn earworm larval growth rates were higher on the vigorous plants and lower on the punched, no fertilizer, no water, and no water and no fertilizer host plants (P<0.01). Regardless of insect species or bioassay method, the results in the tomato system support the plant vigor hypothesis that predicts positive association between insect performance and plant growth. The results contradict the plant stress hypothesis that rank stressed plants as better hosts for insects. The mechanisms involved are a combination of poor nutritional value and chemical defenses. We demonstrate a negative association between plant growth and chemical defense. However, induced response triggered by hole‐punching was not cost effective to the plants.

Remotely sensed land cover temperature and soil water status—a brief review

The temperature of a plant canopy, as seen by a scanning device, is determined by plant physiological processes and environmental conditions which interact in a complex manner not readily monitored by remote sensing devices. The physiology literature is briefly considered with a view to outlining factors that may be relevant in inferring soil water content from canopy temperature. Examples of energy fluxes and temperatures observed under field conditions are discussed.

A new approach to the physiological host plant-parasite relationship — A technique in the field of applied entomology

Less than ten years ago research on the feeding physiology of mites and aphids was hardly developed. Since then there have been a number of investigations about the influence of changes in the chemical composition of the leaves on the population development of insects and mites. It has nevertheless not yet been possible to acquire a useful understanding of this particular problem. This is parry due to the great diversity of the methods applied and parry to the fact that the special food requirements of the majority of parasites are as yet unknown and those known vary greatly. A comparison of the results is therefore extremely difficult and hampers an evalution of the data obtained. Within the framework of the Dutch Study Group on Integrated Control of Pests, the authors have studied the influence of the host plant's physiological condition 2 on the population development of phytophagous insects and mites. By changing the ion-ratio of the nutrient solution on which the plants are grown, chemical changes in the leaves are induced and differences in population development of the parasites can be evaluated. The experiments were set up as balance studies, that is to say, the whole of nutrient solution together with the plants and parasites was arranged as a closed system for certain nutrient elements. The distribution of a certain element over the three components, viz. nutrient solution, plant and phytophagous organism, is influenced by the composition of the solution, the ion uptake capacity of the plant and the food uptake and population density of the parasite. As a closed system was being considered, the initial quantity of the testelement had to equal the sum of the quantities recovered from the three corn

Phenology of the Citrus flowers and their local flowering dates in north Izu region (1)

The investigation of the Citrus flowers is important, not only for fruit-calture but also for phenological study. And if their operating and plant physiological conditions are cleared by some means, the differences of the flowering dates are able to use for the indicator of the climatic conditions. From this point of view the author studied the citrus flowers and came to the conclusions as follows:(1) The date of the first flowering, full blooming and falling of the flowers of Washington navel (C. sinensis OSBECK) come first of all, then Wase Unshu (an early ripe species of C. unshu MARC.), Natsu-daidai (C. natsudaidai HAYATA) and Unshu (C. unshu MARC.) follow in order. Washington navel are 5-6 days, Wase Unshu 2-5 days, and Natsudaidai 1-3 days earlier than Unshu in general.(2) The observed values in 8 years at Okitsu (in this time there are no changes of the operating conditions) lead us to the results as follows:(a) Correlation coefficient between the mean temperature of April or March and April, and the first flowering date of Unshu or Washington navel are about -0.9, as to Natsudaidai about -0.4, Wase Unshu -0.7--0.8, respectively. The experimental formula of Unshu is obtained.K=-8.52T+131.39K: first flowering date in May, T: mean temperature [(may. +min.)÷2]°C of April.(b) It is confirmed that the length of the terms from the first flowering date to full blooming date, and from full blooming date to falling flowers are both long every other year. For this reason, the first flowering date may be better than the other, as the citrus flowers are used to the climatic index.(3) Relations between the first flowering dates and operating conditions are analysed qualitatively: earlier at the more infertile soil, and earlier in the case of the slighter running.(4) The first flowering date also depend upon the age of the tree. The trees that are about 40 years old are the earliest.