Free Proline Content Research Articles

High-Throughput Screening of Free Proline Content in Rice Leaf under Cadmium Stress Using Hyperspectral Imaging with Chemometrics.

Tracking of free proline (FP)—an indicative substance of heavy metal stress in rice leaf—is conducive to improve plant phenotype detection, which has important guiding significance for precise management of rice production. Hyperspectral imaging was used for high-throughput screening FP in rice leaves under cadmium (Cd) stress with five concentrations and four periods. The average spectral of rice leaves were used to show differences in optical properties. Partial least squares (PLS), least-squares support vector machine (LS-SVM) and extreme learning machine (ELM) models based on full spectra and effective wavelengths were established to detect FP content. Genetic algorithm (GA), competitive adaptive weighted sampling (CARS) and PLS weighting regression coefficient (Bw) were compared to screen the most effective wavelengths. Distribution map of the FP content in rice leaves were obtained to display the changes in the FP of leaves visually. The results illustrated that spectral differences increased with Cd stress time and FP content increased with Cd stress concentration. The best result for FP detection is the ELM model based on 27 wavelengths selected by CARS and Rp is 0.9426. Undoubtedly, hyperspectral imaging combined with chemometrics was a rapid, cost effective and non-destructive technique to excavate changes of FP in rice leaves under Cd stress.

SALT TOLERANCE OF OCIMUM BASILICUM CV. GENOVESE USING SALICYLIC ACID, SEAWEED, DRY YEAST AND MORINGA LEAF EXTRACT

To improve the salt tolerance of Genovese cultivar of sweet basil (Ocimum basilicum L.) plants, an experiment was conducted to evaluate the impact of certain growth substances (salicylic acid, seaweed extract, dry yeast and moringa leaf extract) on growth, volatile oil percentage and yield as well as chemical constituents under saline water irrigation stress conditions (control, 1000, 2000 and 4000 ppm NaCl). The obtained results revealed that the higher salinity levels (2000 and 4000 ppm NaCl) caused significant decreases in vegetative growth measurements of basil plants compared to control and the lowest salinity level (1000 ppm NaCl). Maximum reduction was observed at 4000 ppm NaCl which showed higher increase of the total phenolics and free proline contents. All recoded parameters were enhanced for plants grown under 1000 ppm NaCl. Seaweed extract was superior than other treatments in enhancing the plant tolerance to salinity which appeared in the significantly increasing of growth and volatile oil content of basil. Phenolics and proline contents were increased with salicylic acid treatment comparing with other ones. The best combination recommended as a result of the current study is treating basil plants with seaweed extract under low salinity level (1000 ppm) for improving the growth and volatile oil parameters.

Effect of Saline Water Stress in the Presence of Silicon Foliar Application on Growth, Productivity and Chemical Constituents of Chia (Salvia hispanica L.) under Egyptian Conditions

The pot experiment was carried out during two successive seasons (2016/2017 & 2017/2018) to study the effect of five levels of salinity and three levels of silicon (Si), as a foliar-spray application as well as their combinations on growth, productivity and chemical constituents of chia (Salvia hispanica L.) plants. Results showed that there was a negative relationship between vegetative growth measurements i.e., plant height, fresh weight and dry weight, flowering growth and yield parameters i.e., main inflorescence height, main inflorescence weight, inflorescences weight, seeds weights, weight of 1000 seeds and calculated seeds yield /m2 and root growth measurements i.e. root length, root weight and root diameter values and salinity treatments in both seasons. Hence, as the concentrations of salinity increased, the values of these parameters decreased to reach the maximum decreasing at the high concentration (4.69 dS m-1). Therefore, the combination treatment between 0.68 dS m-1 salinity concentration and 2000 ppm silicon scored the highest values of these parameters, in the 1st and 2nd seasons. Meanwhile, the maximum values of N, P and K contents were recorded by the combination treatment between 0.68 dS m-1 salinity concentration and 2000 ppm silicon in both seasons. Whereas, the highest values of free proline, sodium and chloride content were gained by the high concentration of salinity 4.96 dS m-1 especially those received silicon at 0 ppm in both seasons. Conclusively, the highest growth, productivity and chemical constituents of chia (Salvia hispanica L.) plant, it is preferable to grow the plants under saline water irrigation concentration at (0.68 dS m-1) and spray with silicon at 2000 ppm.

Salinity stress response of non‐transformed and AtCKX transgenic centaury (Centaurium erythraea Rafn.) shoots and roots grown in vitro

AbstractCommon centaury (Centaurium erythraea Rafn.) is a plant species that can inhabit saline soils. It is known as a plant with high spontaneous regeneration potential in vitro. In the present work we evaluated shoots and roots salinity tolerance of non‐transformed and three AtCKX transgenic centaury lines to graded NaCl concentrations (0, 50, 100, 150, 200 mM) in vitro. Overexpression of AtCKX genes in transgenic centaury plants resulted in an altered cytokinins (CKs) profile leading to a decline of bioactive CK levels and, at the same time, increased contents of storage CK forms, inactive CK forms and/or CK nucleotides. Significant increment of fresh shoot weight was obtained in shoots of non‐transformed and AtCKX1 transgenic line only on medium supplemented with 50 mM NaCl. However two analysed AtCKX2 transgenic lines reduced shoot growth at all NaCl concentrations. In general, centaury roots showed higher tolerance to salinity than shoots. Non‐transformed and AtCKX1 transgenic lines tolerated up to 100 mM NaCl without change in frequency of regeneration and number of regenerated plants. Roots of two analysed AtCKX2 transgenic lines showed different regeneration potential under salt stress. Regeneration of transgenic AtCKX2‐26 shoots even at 200 mM NaCl was recorded. Salinity stress response of centaury shoots and roots was also evaluated at biochemical level. Free proline, malondialdehyde and hydrogen peroxide content as well as antioxidative enzymes activities were investigated in shoots and roots after 1, 2, 4 and 8 weeks. In general, adition of NaCl in culture medium elevated all biochemical parameters in centaury shoots and in roots. Considering that all analysed AtCKX transgenic centaury lines showed altered salt tolerance to graded NaCl concentrations in vitro it can be assumed that CKs might be involved in plant defence to salt stress conditions.

A little membrane protein with 54 amino acids confers salt tolerance in rice (Oryza sativa L.)

The plasma membrane is critical in sensing, interpreting, and transducing environmental signals. In the present study, we characterized an Oryza sativa salt-responsive little protein 1 (OsSRLP1) in rice, which encodes a plasma membrane localized protein containing 54 amino acid residues. Expression of OsSRLP1 was detected in various rice tissues and was significantly induced by low temperature, drought, and salt. Overexpression of OsSRLP1 in rice improved free proline content and modulated ion balance under salt stress, which resulted in enhanced salt tolerance. Compared to wild-type rice, overexpression of OsSRLP1 inhibited seed germination under normal conditions. Interestingly, OsSRLP1 expression was up-regulated in ABL5-Like1 deficiency mutant abl1 compared to wild-type rice under salt treatment. Moreover, it was observed that overexpression of OsSRLP1 led to the dwarfism phenotype, which was correlated to the OsSRLP1 expression level in transgenic rice. In conclusion, OsSRLP1 is a little membrane protein conferring salt tolerance by modulating the ion balance and proline accumulation in rice.

Levels of induced free proline in chelated and unchelated hydroponically grown lettuce (<i>Lactuca sativa L.</I>)

It is well described that under stress conditions many plant species accumulates proline as adaptive response to adverse conditions. In this study, eight weeks old Lactuca sativa L. seedlings were transplanted in nutrient solution containing various doses (0.000, 0.0025, 0.005, 0.0075, and 0.025mg/L) of Pb2+ and Cd2+ and constant concentration of EDDS (0.0025M). The effects of these treatments of Pb2+, Cd2+, combination of Pb2+ + Cd2+and with or without EDDS (Ethylene diamine disuccinate) were compared based on the level of stress induced to the seedlings. Free proline contents induced due to stress by uptake of Pb2+and Cd2+ were investigated in both unchelated and chelated treatment. The results obtained showed that the effect of increasing concentration of Pb2+ in hydroponic solution leads to decrease in the level of stress induced to the seedlings by EDDS while the lower the Cd2+ concentration in the hydroponic solution the more the level of stress induced by EDDS to the plant. The highest level of stress caused to the seedlings by unchelated and chelated Pb2+ solution are 68.294±5.642; 72.681±14.740 µmolg-1 respectively while that of Cd2+ are 28.962±8.703; 48.263±2.455 µmolg-1 respectively. From this, it is evident that Pb2+induced more stress to the plants than Cd2+ in the presence and absence of EDDS (p<0.05).
 Keywords: Proline, Ethylenediaminedisuccinic Acid (EDDS), Lead, Cadmium, Lettuce.

Proline metabolism and molecular cloning of AmP5CS in the mangrove Avicennia marina under heat stress.

Proline is one of the most important compatible osmolyte in cells, which accumulates in response to various stresses, including salt, water deficit, heavy metal, pathogen infection and extreme temperature. In this study, a growth chamber was employed to simulate heat environment for Avicennia marina seedlings. We detected some physiological indices in the leaves of A. marina at 40 °C, including the activity of delta-1-pyrroline-5-carboxylate synthase (P5CS), the content of free proline and soluble protein, transpiration rate and membrane permeability, and discussed the relationship between these five indices and heat resistant ability. And then a P5CS gene was cloned from A. marina using homologous cloning and rapid amplification of cDNA ends methods. It was designated as AmP5CS, encoding a protein that contained a feedback inhibition site of proline, proA, proB, conserved Leu zipper, GSA-DH domain and other functional domains of P5CS protein in high plants. Expression analysis of AmP5CS gene indicated it was involved in heat stress response. It is the first time that P5CS from A. marina has been cloned and the findings laid the foundation of figuring out heat resistant mechanisms and relieving heat damage, which is significant during global warming.

Chitosan nanoparticle and pyridoxine seed priming improves tolerance to salinity in milk thistle seedling

Application of growth regulators plays important role under salt conditions. Perspectives to overcome these limitations by chitosan nanoparticle (CSNP: 0, 0.25, 0.5, and 1%) and pyridoxine (PN: 0, 0.03, 0.06, and 0.09%) seed priming was studied in both experiments with milk thistle seeds exposed to NaCl as salt stress (0, 50, 100, and 150 mM). Salinity threshold and EC50 (the salinity level that 50% of germination reduction) achieved 74.85 and 213.5 mM, respectively. A significant reduction in germination percentage (49.12%), seedling length (50.07%), and seedling vigor index (67.39%) while, a significant increase in superoxide dismutase activity (54.63%) were achieved at 150 mM NaCl in compared to the control treatment. The highest germination rate was resulted by 100 mM NaCl and 0.25% CSNP and the least (2.86 seed/day) by 150 mM NaCl and without CSNP. The salt stress significantly decreased photosynthetic pigments; however, the largest value of chlorophyll a, b, and total was related to without NaCl and 1% CSNP and the least value of traits (6.1, 1.67, and 7.77 µg/g FW) to non-application of CSNP under 150 mM NaCl. PN application was caused decrease in free proline content compared to the non-application treatment. The most pronounced effects of CSNP and PN were recorded in 0.25 and 0.09% concentrations, respectively. The finding of this study leads to the conclusion that seed priming with CSNP and PN by improving physiological mechanisms such as photosynthetic pigment synthesis, antioxidant enzyme activities, and free proline content increased salt tolerance in milk thistle seedling.

Response of Hyacinthus orientalis L. to salinity caused by increased concentrations of sodium chloride in the soil

Hyacinths are used in flowerbed in cities. Plants are exposed to difficult urban conditions prevailing in winter, including notably to soil salinity resulting mainly from the use of sodium chloride. The aim of the study was analysed the response of Hyacinthus orientalis ‘Delft Blue’ to increased concentrations of sodium chloride in the soil. Pots with bulbs were each treated with 100 cm3 of NaCl aqueous solution at a concentration of either 10 g .dm-3 (dose level 1) or 20 g. dm-3 (dose level 2). Pots were irrigated with the NaCl aqueous solution in September or in January of the following year. After keeping the bulbs at a cool temperature for 12 weeks, the plants were grown in a greenhouse where they were assessed in terms of growth parameters and free proline content. The obtained results showed that the growth and the ornamental qualities of Hyacinthus orientalis ‘Delft Blue’ after treatment with sodium chloride were sufficient for recommending this plant for growing in flower beds exposed to salinity of 6.1-8.6 g dm-3. The leaf greenness index and proline content (in the second season) were greater and the length of forcing period was longer (in the second season), when the sodium chloride was applied to the soil on the day of planting bulbs.

Seed germination, bud growth and heavy-metal accumulation of Suaeda salsa

Nickel and copper, as high toxic heavy metals (HMs), are the most serious contaminants in Jinchuan mining area, China. In this paper, the influence of combined HMs stress on the growth of widespread plant-S. salsa has been studied. The stress gradient of combined Ni-Cu was set based on the local environment and pre-experiment. Seed germination, growth, physiological characteristics of S. salsa were investigated by the control test, and its heavy metal bioaccumulation capacity was investigated by samples collected from field platform. The growth of S. salsa was promoted at lower concentration (≤40 mg/L) and inhibited at higher concentration (≥80 mg/L) under the single HMs stress and combined HMs stress (Cu20/Ni20). The malondialdehyde (MDA) content was increased with increasing concentration, and the soluble protein and free proline content in stress group were higher than that of in control group. Under single HMs stress, the peroxidase (POD) activity increased with increasing concentration; while under combined HMs stress, the POD activity increased initially and then reduced. Cu320 and Ni320 combined HMs stress inhibited the growth of S. salsa at all concentrations. The average translocation factors (TF) of S. salsa were greater than 1.00, and higher in leaves compared to stems. The results of bio-concentration factors (BCF) of S. salsa show that BCF of leaves were larger than that of roots and stems. At lower concentration, the combined HMs stress promoted the growth of S. salsa in comparison to single HMs stress, however, opposite results were obtained at higher concentration. Overall, S. salsa showed high tolerance to Cu and Ni and stronger capabilities of HMs uptake and translocation, and therefore, it can be used as an alternative plant for the bioremediation of heavy metal pollution in mining area.

Effects of potassium chloride and nitric oxide on growth and physiological characteristics of winter wheat under salt stress

A hydroponic culture was conducted to evaluate the effects of KCl and sodium nitroprusside (SNP; a nitric oxide donor) in wheat seedlings under salt stress. Exposure to 100 mM NaCl for 7 d decreased biomass of wheat seedlings, root activity and H+-ATPase activity, significantly increased free proline content, reactive oxygen species (ROS) accumulation and lipid peroxidation, and suppressed the activity of superoxide dismutase (SOD). Moreover, NaCl stress significantly decreased the K+ and increased the Na+ content. Addition of KCl or SNP led to the increase in root activity and soluble protein content, stimulated the activity of SOD, and decreased free proline content, superoxide anion radical generation rate, and lipid peroxidation. The increased K+ and decreased Na+ content in the leaves of treated seedlings indicated that suitable KCl and NO addition stimulated the selective transport of K+ and Na+ to the maintain K+/Na+ homeostasis.

Effects of sodium benzoate on growth and physiological characteristics of wheat seedlings under compound heavy metal stress

In this study, we investigated the effect of exogenous sodium benzoate on wheat seedlings (Yangmai 16) grown under heavy metal stress. The results showed that 2.4 mmol kg−1 of heavy metals significantly inhibited growth and delayed emergence of wheat seedlings. Under compound heavy metal stress, application of 2–4 g L−1 sodium benzoate significantly increased (P>0.01) chlorophyll content and chlorophyll fluorescence parameters Fv/Fm and Fv/Fo of wheat, compared to the control (water treatment). Further analysis showed that application of 2–4 g L−1 sodium benzoate alleviated osmotic stress by promoting the accumulation of osmolytes such as soluble proteins and free proline, increased the activity of superoxide dismutase (SOD) and reduced malondialdehyde content (MDA). In contrast, higher concentrations of sodium benzoate solution (>6 g L−1) inhibited the growth of wheat seedlings and even caused damage to seedlings. Correlation analysis showed that when the sodium benzoate concentration was in the range of 1.97–3.12 g L−1 (2016) and 1.58–3.27 g L−1 (2017), values of chlorophyll and its components, root activity, SOD activity, soluble protein, and free proline content were the highest. When the sodium benzoate concentration was raised to 2.59 g L−1 (2016) or 3.02 g L−1 (2017), MDA content was the lowest. Ultimately, exogenous sodium benzoate (2–4 g L−1) facilitates root development and improves the root activity of wheat seedlings grown under compound heavy metals stress, thereby effectively alleviating the damage of compound heavy metal stress in wheat seedlings.

ABA-dependent K+ flux is one of the important features of the drought response that distinguishes Catalpa from two different habitats

ABSTRACTAbscisic acid (ABA)-induced stomatal closure can improve drought tolerance in higher plants. However, the relationship between ABA-related ion flux and improved drought resistance in the roots of woody plants is unclear. To investigate this relationship, we employed a noninvasive micro-test technique (NMT) to detect potassium (K+) flux in Catalpa fargesii and C. fargesii f. duclouxii after treatment with polyethylene glycol (PEG) and ABA. PEG treatment slightly increased the free proline content in both Catalpa species. However, simultaneous treatment with ABA and PEG resulted in a large increase in free proline content. Treatment with PEG led to a significant increase in K+ efflux, and both ABA and tetraethylammonium (TEA, a K+ channel inhibitor) blocked this efflux under short-term (1 d) and long-term (7 d) drought conditions. Furthermore, we detected SKOR (stelar K+ outward-rectifying channel) gene expression in roots, and the results showed that PEG significantly increased SKOR expression in C. fargesii f. duclouxii, but SKOR expression was inhibited by ABA in Catalpa fargesii. These findings indicate that ABA improves drought tolerance by inhibiting K+ efflux in Catalpa, but distinct ABA response patterns exist. Drought-tolerant species have better potassium retention are dependent on ABA, and can accumulate more proline than other species. SKOR is also ABA-dependent and sensitive to ABA, and K+ flux is a target of the ABA-mediated drought response.

Effect of Cattle Manure on Young Plants of Khaya senegalensis Submitted to Different Irrigation Intervals

This study aimed to evaluate the effect of cattle manure on young plants of Khaya senegalensis submitted to different irrigation intervals. A greenhouse experiment was carried out during 2017 cold season, based in a 5x3 factorial arrangement – cattle manure fertilizing with 0, 10, 20, 30 and 40% doses, and 3-day, 6-day and 12-day irrigation intervals. Water potential, relative water content (RWC), water consumption (WC), water use efficiency (WUE), chlorophyll content estimation (SPAD index), plant height, stem diameter, plant total dry mass and free amino acid and proline content were measured. Irrigation intervals had no significant effect on physiological traits and plant water relationships, except for WUE, which was higher under 12-day irrigation interval. This was assumed as an indication of non-occurrence of water stress, even under the longest irrigation interval. Cattle manure, in turn, played a significant effect on these traits, except for water potential, irrespective of irrigation intervals. Increasing cattle manure doses improved RWC (just doses up to 20%), reduced WC and increased WUE, SPAD index, and both free amino acid and proline contents. On the other hand, growth-related parameters were not affected by cattle manure, but a significant effect of irrigation intervals was observed. Both plant height and total dry mass were lower under 3-day and 6-day irrigation intervals. We suspect a possibly low evapotranspiration, given the relatively low temperatures of that season (14-16 ºC), which may have reduced the demand for irrigation in the experimental period. Thus, soil moisture under the shorter irrigation intervals may have increased until reach to a close to saturation level, limiting the amount of soil oxygen and hampers nutrient uptake.

Effect of Drought Stress at Reproductive Stages on Growth and Nitrogen Metabolism in Soybean

This study aims to determine variability among soybean (Glycine max (L.) Merr.) cultivars under drought conditions and how nitrogen metabolites, metabolism-related enzymes, and gene expression vary during soybean growth. Three soybean cultivars, Shennong17 (CV.SN17), Shennong8 (CV.SN8), and Shennong12 (CV.SN12), were grown in pot culture and subjected to drought stress at reproductive stages for 45 days. The results showed that long-term drought stress decreased biomass allocation to reproductive organs, weakened antioxidant capacity, and reduced seed weight, effects that were less pronounced in CV.SN12 compared with those in CV.SN8 and CV.SN17. Drought stress decreased the concentrations of nitrogen and soluble protein but increased nitrate concentration in leaves. This was related to the significantly reduction of nitrogen metabolism efficiency, including decreased activities of nitrogen metabolism enzymes, and downregulated expression of GmNR, GmNiR, GmGS, and GmGOGAT. Drought stress increased the concentrations of free amino acid, proline, and soluble sugar in leaves to enhance the osmotic adjustment ability. Furthermore, soybean seed weight showed significantly correlation (p < 0.05) with nitrogen-metabolism-related parameters. Based on the performance of growth, nitrogen metabolism, and yield attributes, CV.SN12 showed the highest tolerance to drought, followed by CV.SN8 and CV.SN17. In addition, these nitrogen-metabolism-related parameters could be used in soybeans to select for drought tolerance.

Sodium chloride facilitates the secretohalophyte Atriplex canescens adaptation to drought stress

Atriplex canescens is a C4 shrub with excellent adaptation to saline and arid environments. Our previous study showed that the secretion of excessive Na+ into leaf salt bladders is a primary strategy in salt tolerance of A. canescens and external 100 mM NaCl can substantially stimulate its growth. To investigate whether NaCl could facilitate Atriplex canescens response to drought stress, five-week-old seedlings were subjected to drought stress (30% of field water capacity) in the presence or absence of additional 100 mM NaCl. The results showed that, under drought stress, the addition of NaCl could substantially improve the growth of A. canescens by increasing leaf relative water content, enhancing photosynthetic activity and inducing a significant declined leaf osmotic potential (Ψs). The addition of NaCl significantly increased Na+ concentration in leaf salt bladders and the Na+ contribution to leaf Ψs, while had no adverse effects on K+ accumulation in leaf laminae. Therefore, the large accumulation of Na+ in salt bladders for enhancing osmotic adjustment (OA) ability is a vital strategy in A. canescens responding to drought stress. In addition, the concentration of free proline, bataine and soluble sugars exhibited a significant increase in the presence of NaCl under drought stress, and the betaine contribution to leaf Ψs was significantly increased by additional NaCl compared with that under drought treatment alone, suggesting that compatible solutes are also involved in OA in addition to functioning as protectants to alleviate water deficit injury.

Cold plasma treatment to release dormancy and improve growth in grape buds: a promising alternative to natural chilling and rest breaking chemicals

Winter dormancy of temperate zone perennial plant species is commonly released by chilling temperature. If the duration of the cold weather is not adequate, plant growth becomes disorganized leading to reduced growth, spread out flowering and fruit maturation and often reduced yield. In mild-winter regions, growers commonly resort to spraying their trees with chemicals such as hydrogen cyanamide to compensate for the lack of chilling to ensure good growth and yield. Although effective, most of these chemicals are highly toxic; unfortunately, there is no effective and environmentally friendly alternative which can be used to release dormancy. In this work, we present a cold plasma treatment-based method which can effectively release the dormancy of grape buds. We have found that exposing grape buds to plasma provides improvement of several growth parameters including higher, faster and more synchronous budbreak and more vigorous vegetative growth, comparatively similar to or better than natural chilling. Biochemical analyses of bud tissue suggest that the plasma treatment triggered a marked transient oxidative stress as indicated by the increase in the concentrations of free proline, malondialdehyde (MDA) and hydrogen peroxide (H2O2). Proline appears to have played a key role; as a compatible osmolyte, it may have protected cellular structures against free radicals and as a signaling molecule, it may have induced the events leading to dormancy release. We anticipate that our work will provide a starting point for the development of novel plasma-based tools and methods to treat dormant plants. The plasma treatment method may allow higher agricultural production in several regions of the world at risk of becoming marginal for the cultivation of certain crops due to global warming.

Acúmulo de solutos orgânicos em mudas de Ceiba glaziovii (Kutze) Kum. em resposta à seca intermitente

Ceiba glaziovii (Kuntze) K. é uma espécie ocorrente na Caatinga de importância econômica e ecológica. Contudo, o conhecimento da sua fisiologia em resposta à períodos de seca, na fase inicial do desenvolvimento, não são bem conhecidas. O presente trabalho objetivou avaliar o teor relativo de água das folhas e o acúmulo de solutos orgânicos osmoticamente ativos em mudas de Ceiba glaziovii submetidas à seca intermitente. Para tal, mudas de um mês de idade de C. glaziovii foram submetidas à seca intermitente por ciclos de suspensão da irrigação [rega diária (C), irrigação a cada sete dias (E7), suspensão de rega até sinais de murcha como estresse severo (ES) e reirrigadas (RE), verificando a recuperação após 72 horas]. Avaliou-se a altura das plantas, o diâmetro do caule, teor relativo de água nas folhas, a concentração de prolina livre (PL), carboidratos (CS) e proteínas (PS) nas folhas e raízes. A seca intermitente exerceu pouco efeito sobre o TRA das mudas de C. glaziovii, porém afetou negativamente o crescimento delas. Não houve acúmulo de CS nas folhas, porém houve grande variação na concentração de PL e PS. Nas raízes das plantas E7 houve acúmulo significativo de CS, PL e PS, evidenciando o papel desses compostos no ajustamento osmótico no sistema radicular. A Ceiba glaziovii consegue manter valores adequados de água nos tecidos em situação de seca intermitente, durante o período inicial do desenvolvimento. A prolina se acumula nas folhas e raízes em resposta ao déficit hídrico moderado, sugerindo um papel importante para a sobrevivência da espécie.

Foliar Application of Polyamines Modulates Winter Oilseed Rape Responses to Increasing Cold.

Cold stress is one of the most common abiotic stresses experienced by plants and is caused by low temperature extremes and variations. Polyamines (PAs) have been reported to contribute in abiotic stress defense processes in plants. The present study investigates the survival and responses of PA-treated non-acclimated (N) and acclimated (A) winter oilseed rape to increasing cold conditions. The study was conducted under controlled conditions. Seedlings were foliarly sprayed with spermidine (Spd), spermine (Spm), and putrescine (Put) solutions (1 mM) and exposed to four days of cold acclimation (4 °C) and two days of increasing cold (from −1 to −3 °C). Two cultivars with different cold tolerance were used in this study. The recorded traits included the percentage of survival, H+-ATPase activity, proline accumulation, and ethylene emission. Exogenous PA application improved cold resistance, maintained the activity of plasma membrane H+-ATPase, increased content of free proline, and delayed stimulation of ethylene emission under increasing cold. The results of the current study on winter oilseed rape revealed that foliar application of PAs may activate a defensive response (act as elicitor to trigger physiological processes), which may compensate the negative impact of cold stress. Thus, cold tolerance of winter oilseed rape can be enhanced by PA treatment.

Effect of NaCl-Induced Salinity Stress on Growth, Osmolytes and Enzyme Activities in Wheat Genotypes.

Effect of NaCl-induced salinity stress was studied on three wheat (Triticum aestivum L.) genotypes (Platinum Lok 1, Eagle 135 and Kisan farmer). Seedling growth characteristics, chlorophyll contents, lipid peroxidation (MDA contents), proline, glycine betaine (GB) and the activities of catalase and peroxidase enzymes were evaluated at the seedling stage. The magnitude of reduction in growth parameters and chlorophyll contents was less in Platinum Lok 1 as compared to Kisan Farmer and Eagle 135. Platinum Lok 1 exhibited the highest increase in free proline and GB contents under NaCl stress as compared to the other two genotypes. Compared to Platinum Lok 1 and Eagle 135, Kisan Farmer accumulated more MDA contents under salinity stress. The enzyme activities were significantly higher in Platinum Lok 1 when compared to the other two genotypes. Therefore, these parameters could provide useful markers for the identification of salinity stress tolerant wheat genotypes at the seedling stage.