Cyanide is uncontrollably produced in some industrial operations and has lethal effects on humans and the environment. Since removing processes of cyanide are complicated and costly, the phytoremediation has recently been extensively considered. To achieve an increased cyanide resistance, which is needed for an efficient phytoremediation of the mediums with high concentrations of cyanide, the effects of salicylate as a phytohormone were studied. Cuttings of Salix babylonica, as a model plant, were used in a completely randomized design with three replicates in hydroponics using a modified Hoagland nutrient solution. Plants were pretreated with sulfosalicylate (0, 5, 10 and 15 mg L-1) for 21 days and then were treated with toxic concentration of cyanide (9 mg CN- L-1); some of the physiological indices which show cyanide toxicity/resistance were measured. Favorable responses to salicylate toward the increase in resistance to cyanide were concentration dependent which were observed at 10 mg L-1 sulfosalicylate and it was accompanied with an increase in superoxide dismutase activity and reducing the capacity of root extract. Dehydrogenase activity and electrolyte leakage from roots were decreased relating to control plants. It also prevented the cyanide inhibitory effect on oxygen consumption. The observed effects could be attributed to redox status and alteration of production and scavenging of reactive oxygen species by salicylate and cyanide. The results indicated that a proper concentration of salicylate could be used as a cyanide resistance stimulator in willows.

Stresses can cause large yield reductions in cultivated plants. The response to these stresses occurs via a plethora of signalling pathways, where a large number of genes is induced or repressed. Among the environmental stress responsive genes, there are the members of the ethylene response factors (ERF) gene family. The mRNA levels of different ERF are regulated by many hormones and molecules produced under different stress conditions. In this study, with the goal of identifying the response of rice ERF genes to environmental stress, it was analysed the transcriptional expression profile of 114 of these genes under stress by anoxia, salt and Magnaporthe grisea. Also, aiming to characterize how the regulation of ERF genes occurs, the amount of known cis regulatory elements in the promoter region of these genes and their association with the expression profiles under the tested conditions were also assessed. The results indicate that some ERF members present the same specific expression profiles under different environmental stresses, while others do not. Within the ERF family, the regulation of gene expression is complex for some genes which have many cis elements in their promoters, but simple for others, demonstrating high levels of divergence among them. The findings demonstrate the importance of the study of each ERF separately, since it is not possible to establish general rules for regulation and probably for the function of these genes.

Hydrogen peroxide (H2O2) is an essential signaling molecule that mediates plant responses against several biotic and abiotic stresses. H2O2 pretreatment has emerged as a signaling way, inducing salt stress acclimation in plants. Here, we analyzed the effects of H2O2 leaf pretreatment on the non-enzymatic defense system (ascorbate and glutathione), plant growth, relative water content (RWC), relative chlorophyll content, H2O2 content, and gas exchange in maize plants under NaCl stress. The results showed that salinity reduced the leaf area and shoot and root dry mass as compared to control, and the leaf spraying with H2O2 significantly improved the growth of salt stressed plants. Photosynthesis and transpiration, stomatal conductance and intercellular CO2 concentration were strongly decreased by salinity after 7 and 14 days of salt exposure; however, the decrease was lower in plants sprayed with H2O2. The improved gas exchange in H2O2-sprayed stressed plants correlated positively with higher RWC and relative chlorophyll content and lower leaf H2O2 accumulation under NaCl stress conditions. Ascorbate and glutathione did not play any obvious effects as non-enzymatic antioxidants in the ROS scavenging. In conclusion, the salt tolerance induced by H2O2 leaf pretreatment is attributed to a reduction in the H2O2 content and maintenance of RWC and chlorophyll in maize leaves. These characteristics allow maize plants to maintain high rates of photosynthesis under salt stress and improve the growth.

The present research was conducted to evaluate the interaction effects of exogenous abscisic acid (ABA) and salt stress on phenolic compounds, growth and yield of two short day strawberry cvs "Queen Elisa" and "Kurdistan". Plants were subjected to control, gradual salt stress (up to 20 mmol L-1 over 5 weeks) and salinity shock (20 mmol L-1). ABA treatments included: 0 (control), 5, 10, 20 and 40 µmol L-1. The experiment was carried out based on a complete randomized design in factorial experiment. The highest level of ferulic acid was observed by applying 40 µmol L-1 ABA in "Queen Elisa" under salt stress shock but effective increase in caffeic acid and p-coumaric acid was shown at gradual salt stress for both cultivars at the same ABA level. Maximum level of ABA led to the highest gentisic acid and gallic acid at gradual salt stress in "Kurdistan". Methyl gallate and flavonoid content showed a striking increase at the same conditions in "Queen Elisa". The interaction effect of salt stress regimes and ABA resulted in an increase in ellagic acid content for both cultivars. The interaction effect of ABA and salt shock caused higher reduction in root and shoot fresh dry weights and decrease in fruit yield in "Kurdistan". The results of this experiment accounts for the important role of exogenous ABA in the activation of antioxidant defense mechanism, growth and yield maintenance under gradual salt stress in strawberry.

The objective of the present study was to understand the relationship among leaf morphology, stomatal characteristics and water relations in triploids generated through anther culture and their counterpart diploid plant of C. clementina. Triploid plants possessed small and narrow leaves as compared to diploid plant as evident by less leaf length, leaf width and leaf area. By contrast, the leaf index was observed to be more in triploids than haploid ones. Flow cytometric analysis re-confirmed the ploidy levels of heterozygous plant Hd as diploid and the ploidy of Th1, Th2, Th3 and Th4 plants as triploids. A positive relation was found between ploidy level and stomatal guard cell length and width, whereas a negative relation was observed between the stomata density and ploidy level. The stomatal density was reported to be 6.2±0.2 stomata per µm² in diploid plant, while stomatal density varied between 3.0 and 3.6 stomata per µm² in triploids. Leaf relative water content (RWC) was slightly higher in triploids (90.8 to 93.1%) than diploid (89.5%). The leaf water loss was found to be marginally higher in diploid than in triploid plants. Our results show that increase in ploidy level from diploids to triploids caused an effect on leaf morphology and stomatal characteristics with probable consequences to water relations of leaves. This research will serve as an important basis for future work on complete analysis of both morphological and behavioural traits of the leaf stomata and transpiration rates in relation to diploid versus triploid plants.

Since the beginning of Human civilization, the soil organic matter has been used as plant growth promoter and/or regulator. Indeed, early in plant science history, even before the auxin concept has been established, the term "auximones" was coined to describe plant growth promoting humic acids derived from peat. Despite of this, until the end of the 20th century, humic substances remained as some of the most neglected environment signals in plant physiology research. However, this scenario has changed in last decade with the discovery that the major systems of energy transduction of the plant cell membranes, the proton pumps, can be tightly orchestrated by humic substances just as elicited by a hormonal signaling. Differential activations of both plasma membrane (PM H+-ATPase) and vacuolar pumps (V-ATPase and H+-PPase) are modulated by humic substances triggering ion signatures related to specific patterns of plant growth and development. Phytohormones have been found to be associated with this humus bioactivity, and nitric oxide acting as a second messenger in a signaling pathway in which plants can sense the soil environment to cope with specific conditions. In this review, we discuss some of the most influential data available in literature, which have shaped this underexplored interface between the chemistry of the organic matter and the plant physiology. The key role of organic matter in the sustainable agriculture will also be highlighted from a biochemical perspective of the plant cell responses to biofertilization, specially in tropical environments.

The shade leaves of coffee (Coffea arabica L.) apparently retain a robust photosynthetic machinery that is comparable to that of sun leaves and can fix CO2 at high rates when subjected to high light intensities. This raises the question of why the coffee plant would construct such a robust photosynthetic machinery despite the low photosynthetic rates achieved by the shade leaves at low light supply. Here, we grew coffee plants at 100% or 10% full sunlight and demonstrated that the shade leaves exhibited faster photosynthetic induction compared with their sun counterparts, in parallel with lower loss of induction states under dim light, and were well protected against short-term sudden increases in light supply (mimicking sunflecks). These findings were linked to similar photosynthetic capacities on a per mass basis (assessed under nonlimiting light), as well as similar extractable activities of some enzymes of the Calvin cycle, including Rubisco, when comparing the shade and sun leaves. On the one hand, these responses might represent an overinvestment of resources given the low photosynthetic rates of the shade leaves when light is limiting; on the other hand, such responses might be associated with a conservative behavior linked to the origin of the species as a shade-dwelling plant, allowing it to maximize the use of the energy from sunflecks and thus ultimately contributing to a positive carbon balance under conditions of intense shading.

Rock field plant species present several adaptations to the climatic characteristics and seasonality of this habitat. In this study, we evaluate under field conditions the seasonal changes in non-structural carbohydrate accumulation in tuberous organs of Gomphrena marginata. Tuber fragments of plants of G. marginata were sampled monthly for a year (August 2010 to July 2011) in a rock-field area in southeastern Brazil. Quantitative analyses of total fructose, fructo-oligosaccharides, fructo-polysaccharides, reducing sugars and free proline were carried out. Qualitative analyses of carbohydrates were also performed by thin layer chromatography (TLC) and high performance anion exchange chromatography (HPAEC/PAD). Soil moisture was evaluated by gravimetry and plant water status was evaluated by measuring the relative water content (RWC) and water potential (Ψw) of underground organs. Throughout the analyzed period, a well-marked seasonality of fructan accumulation was observed in tuberous roots of G. marginata correlating significantly with seasonal changes in soil water availability. In the rainy period (October to February), the content of fructo-polysaccharides decrease while during the dry and quiescent growth period (April to September) a high accumulation of fructo-polysaccharides was observed without changes in the RWC of tuberous roots, suggesting that cell osmoregulation contributed to water status maintenance in G. marginata. Our study presents a second species of Amaranthaceae that accumulates fructans as its main reserve carbohydrate, which can be an important strategy for survival in an environment characterized by a long dry period.

An adequate mineral nutrition is essential for the development and productivity of pineapple. However, little is known about the nutritional and metabolic changes that occur in this crop in response to micronutrient deficiency or excess, particularly on tropical conditions. Thus, the objective of this study was to evaluate the application effects of micronutrients in soil and in leaf on biochemical responses of leaves during the development cycle of the pineapple crop. Samples were collected at 3, 6, 9, 12, and 17 months after transplantation. Leaf soluble carbohydrates and N-aminosoluble compounds were determined, as well as variations in the titratable acidity and pH. The soil and leaf micronutrient application increased the concentrations of carbohydrates and N-aminosoluble and reduced the leaf pH, and the changes were more significant in the last sampling (17 months after transplantation). Reductions in concentrations of carbohydrates and increase in the titratable acidity of the pineapple leaves collected at the end of the night were also observed, a fact that reflects the metabolism of Crassulacean acid metabolism species. The strategy of micronutrient application contributes positively to alter the metabolism of plants of pineapple cv. Victoria, especially during flowering and fruit development.

Low temperatures negatively impact the metabolism of orange trees, and the extent of damage can be influenced by the rootstock. We evaluated the effects of low nocturnal temperatures on Valencia orange scions grafted on Rangpur lime or Swingle citrumelo rootstocks. We exposed six-month-old plants to night temperatures of 20ºC and 8ºC under controlled conditions. After decreasing the temperature to 8ºC, there were decreases in leaf CO2 assimilation, stomatal conductance, mesophyll conductance and CO2 concentration in the chloroplasts, in plant hydraulic conductivity and in the maximum electron transport rate driven ribulose-1,5-bisphosphate (RuBP) regeneration in plants grafted on both rootstocks. However, the effects of low night temperature were more severe in plants grafted on Rangpur rootstock, which also presented reduction in the maximum rate of RuBP carboxylation and in the maximum quantum efficiency of the PSII. In general, irreversible damage due to night chilling was found in the photosynthetic apparatus of plants grafted on Rangpur lime. Low night temperatures induced similar changes in the antioxidant metabolism, preventing oxidative damage in citrus leaves on both rootstocks. As photosynthesis is linked to plant growth, our findings indicate that the rootstock may improve the performance of citrus trees in environments with low night temperatures, with Swingle rootstock improving the photosynthetic acclimation in leaves of orange plants.

The non-invasive, magnetic leaf patch clamp pressure probe (also termed ZIM-probe) allows for the first time to measure continuously turgor pressure changes of plant leaves over long periods of time with high precision and in real time. The probe has become an important tool in plant physiology, molecular biology and ecology, but also in agriculture because the probe is very robust and user-friendly. Growers receive the information about the water status of their plants by wireless telemetry, mobile network and internet on an as-needed basis and can thus adjust very precisely both the timing of irrigation and the quantity of water to apply. Effects of air and leaf temperature, relative humidity, illumination and wind on turgor pressure can be monitored very sensitively both under indoor and outdoor conditions. Even the effects of blue and red light as well as of oscillations of stomata aperture on turgor pressure can be monitored by the probe with high sensitivity. Similarly, water deficit due to increase of the osmotic pressure in the nutrition solutions resulted in significant changes of the probe signals. Multiple probe readings open up new possibilities to resolve (together with other techniques) the mechanisms of short- and long-distance water transport, particularly how plants can cope with water shortage. The applications of the magnetic probe are numerous and one can expect highly interesting developments in plant water relations in the nearest future.

Plants in natural environments are subjected to a multitude of environmental cues. However, studies addressing physiological analyzes are usually focused on the isolation of a stress factor, making it difficult to understand plants behavior in their extremely complex natural environments. Herein, we analyzed how environmental variability (noise) may influence physiological processes of Glycine max under water deficit conditions. The plants were kept in a greenhouse (semi-controlled environment - E SC) and in a growth chamber (controlled environment - E C) under two water regime conditions (100 and 30% of replacement of the water lost by evapotranspiration) for 30 days. The environmental variability was daily monitored with automatic sensors to record temperature, humidity, and irradiance. The physiological responses were analyzed by leaf gas exchanges, chlorophyll fluorescence, biomembrane integrity, and growth parameters. The results showed that water deficiency caused significant reductions in the physiological parameters evaluated. However, the environment with high variability (E SC) caused more extensive damages to biomembranes, regardless the water regime likely compromising physiological efficiency. The lower variability of E C promoted higher efficiency of total biomass production in both water regimes compared to the E SC. Therefore, our results support the hypothesis that more variable environmental conditions can limit the growth of Glycine max in response to the fluctuation of resources, therefore amplifying the effect of water deficit.

Oleoresin is a key defense strategy of advanced gymnosperms, based on the combination of a complex anatomical structure of resin ducts and elaborate terpene biochemistry. Given the vast array of oleoresin economic applications in the chemical, pharmaceutical, agrochemical, and biofuel industries, translating factors that regulate terpene biosynthesis into higher oleoresin yield is a challenge for the forestry industry. Field tests with approximately 3,500 28-year-old slash pine (Pinus elliottii Engelm. var. elliottii) trees were carried out from 2005 to 2008, under the subtropical climate of Southern Brazil, in order to examine the seasonal profile of oleoresin production stimulation in response to different chemical adjuvants, after mechanical injury. Yields of trees treated with oleoresin-inducing pastes containing alternative adjuvants were compared to the standard commercial one used on an industrial scale (based on the ethylene-releasing compound - 2-chloroethylphosphonic acid - CEPA). Significant increases in pine oleoresin yield were observed by modulating its biosynthesis and using chemical stimulants affecting defense responses (benzoic acid, used in addition to CEPA) and biosynthetic enzymes (metal cofactors of terpene synthases, iron or potassium, used as replacements for CEPA). Oleoresin stimulation was consistent over at least four consecutive years. Overall effectiveness of oleoresin yield adjuvant stimulation was higher in the faster growth seasons, although potassium was effective in all of them. Combining metal cofactors did not show synergistic or additive interactions. The results suggest that higher oleoresin yields can be obtained by using individual adjuvants of the same signaling pathway in a season-specific fashion.