Salt-induced modulation in growth,photosynthesis and antioxidant system in two varieties of Brassica juncea

The present study was carried out to examine salt-induced modulation in growth, photosynthetic characteristics and antioxidant system in two cultivars of Brassica juncea Czern and Coss varieties (Varuna and RH-30). The surface sterilized seeds of these varieties were sown in the soil amended with different levels (2.8, 4.2 or 5.6 dsm⁻¹) of sodium chloride under a simple randomized block design. The salt treatment significantly decreased growth, net photosynthetic rate and its related attributes, chlorophyll fluorescence, SPAD value of chlorophyll, leaf carbonic anhydrase activity and leaf water potential, whereas electrolyte leakage, proline content, and activity of catalase, peroxidase and superoxide dismutase enzymes increased in both the varieties at 30 d stage of growth. The variety Varuna was found more resistant than RH-30 to the salt stress and possessed higher values for growth, photosynthetic attributes and antioxidant enzymes. Out of the graded concentrations (2.8, 4.2 or 5.6 dsm⁻¹) of sodium chloride, 2.8 sm⁻¹ was least toxic and 5.6 dsm⁻¹ was most harmful. The variation in the responses of these two varieties to salt stress is attributed to their differential photosynthetic traits, SPAD chlorophyll value and antioxidant capacity, which can be used as potential markers for screening mustard plants for salt tolerance.     

Response of two mustard (<Emphasis Type="Italic">Brassica juncea</Emphasis> L.) cultivars differing in photosynthetic capacity subjected to proline

The present paper deals with the effect of exogenous application of proline as a shotgun approach on growth, photosynthesis, and antioxidative system in 25-day-old plants of two different cultivars of Brassica juncea L. (Varuna and RH-30) under natural conditions. Exogenous application of proline significantly increased plant growth, photosynthetic rate, and the activities of antioxidant enzymes, compared with untreated seedlings. Pre-sowing seed soaking in 20 mM proline, for 8 h, proved best among all the other concentrations used.     

Photosynthetic activity, pigment composition and antioxidative response of two mustard (Brassica juncea) cultivars differing in photosynthetic capacity subjected to cadmium stress

Photosynthetic performance, contents of chlorophyll and associated pigments, cellular damage and activities of antioxidative enzymes were investigated in two mustard (Brassica juncea L.) cultivars differing in photosynthetic capacity subjected to cadmium (Cd) stress. Exposure to Cd severely restricted the net photosynthetic rate (P(N)) of RH-30 compared to Varuna. This corresponded to the reductions in the activities of carbonic anhydrase (CA) and ribulose-1,5-bisphosphate carboxylase (Rubisco) in both the cultivars. Decline in chlorophyll (Chl) (a+b) and Chl a content was observed but decrease in Chl b was more conspicuous in Varuna under Cd treatments, which was responsible for higher Chl a:b ratio. Additionally, the relative amount of anthocyanin remained higher in Varuna compared to RH-30 even in the presence of high Cd concentration, while percent pheophytin content increased in RH-30 at low Cd concentration. A higher concentration of Cd (100 mg Cd kg(-1) soil) resulted in elevated hydrogen peroxide (H(2)O(2)) content in both the cultivars. However, Varuna exhibited lower content of H(2)O(2) in comparison to RH-30. This was reflected in the increased cellular damage in RH-30, expressed by greater thiobarbituric acid reactive substances (TBARS) content and electrolyte leakage. The enhanced activities of antioxidative enzymes, ascorbate peroxidase (APX), catalase (CAT) and glutathione reductase (GR) and also lower activity of superoxide dismutase (SOD) in Varuna alleviated Cd stress and protected the photosynthetic activity.     

Increased activity of ATP-sulfurylase and increased contents of cysteine and glutathione reduce high cadmium-induced oxidative stress in mustard cultivar with high photosynthetic potential

Cadmium is known to reduce photosynthesis and overall growth of plants. Plants adopt several mechanisms of Cd detoxification, such as accumulation of sulfur-rich compounds, like glutathione (GSH) and its precursor cysteine. The accumulation of GSH is regulated by the activity of ATP-sulfurylase, a rate-limiting enzyme in sulfur assimilation. The carbon of Cys is provided through photosynthesis. Thus, a plant with the higher photosynthetic potential and ATP-sulfurylase activity may have the higher contents of Cys and GSH and therefore may provide for a greater tolerance to Cd stress. Mustard (Brassica juncea L. Czern and Coss.) cvs. Varuna (high photosynthetic potential) and RH30 (low photosynthetic potential) were subjected to 0 and 200 mg Cd/kg soil, and the activity of ATP-sulfurylase, the contents of Cys and GSH, oxidative stress, and activities of antioxidant enzymes were studied. Under 200 mg Cd/kg soil, cv. Varuna showed an increased ATP-sulfurylase activity, the higher contents of Cys and GSH, and the net photosynthetic rate than cv. RH30. In contrast, the activity of superoxide dismutase, the contents of thiobarbituric acid-reactive substances, and H₂O₂, and electrolyte leakage were found to be greater in cv. RH30 showing an increased oxidative stress than cv. Varuna. However, the activities of ascorbate peroxidase and glutathione reductase were greater in cv. Varuna than cv. RH30. The results show that a greater ATP-sulfurylase activity, an enhanced production of Cys and GSH, and an efficient antioxidant enzyme system in the high photosynthetic mustard cv. Varuna helped to the reduce the oxidative stress maintaing high photosynthesis.     

Differential cadmium stress tolerance in five indian mustard (Brassica juncea L.) cultivars: An evaluation of the role of antioxidant machinery

The presence of Cadmium (Cd) in the agricultural soils affects horticultural cultivars and constrains the crop productivity. A pot experiment was performed using five cultivars of mustard (Brassica juncea L.) to evaluate the difference in their response to Cd toxicity under greenhouse conditions. The pots containing reconstituted soil were supplied with different concentration of CdCl₂ (0, 25, 50, 100 or 150 mg Cd kg⁻¹ soil). Increasing concentration of Cd in the soil resulted in decreased growth, photosynthesis and yield. Maximum significant reduction in growth, photosynthesis and yield were observed with 150 mg Cd kg⁻¹ soil in all the cultivars. Our results indicate that the cultivar Alankar is found to be more tolerant to Cd stress, recording higher plant dry mass, net photosynthesis rate, associated with high antioxidant activity and low Cd content in the plant leaves and thus less oxidative damage. Cultivar RH30 experienced maximum damage in terms of reduction in growth, photosynthesis, yield characteristics and oxidative damage and emerged as sensitive cultivar. The data of tolerance index of Alankar were found to be higher among all tested mustard cultivars which indicate its higher tolerance to Cd. Better coordination of antioxidants protected Alankar from Cd toxicity, whereas lesser antioxidant activity in RH30 resulted in maximum damage. Cultivars of mustard were ranked with respect to their tolerance to Cd: Alankar > Varuna > Pusa Bold > Sakha > RH30, respectively.Key words: antioxidants, cadmium, growth, mustard cultivars, photosynthesis, stress, yield     

Characterization of <Emphasis Type="Italic">Brassica juncea</Emphasis> antioxidant potential under salinity stress

Present study characterizes the anti-oxidative defense potential of four Brassica juncea varieties, Pusa Jaikisan, Varuna, RLM-198, and CS-52, differing in their ability to withstand salinity stress. 7-day-old seedlings raised in MS medium supplemented with 0, 50, 100, and 150 mM NaCl were used to monitor changes in the growth profile, level of stress marker molecules, and activities of important antioxidant enzymes. Increasing NaCl concentration resulted in a significant (P ≤ 0.05) reduction of shoot fresh and dry mass and vigor index in all the varieties tested. Maximum reduction in growth was recorded for RLM-198 while CS-52 maintained better growth characteristics. Varuna and RLM-198 exhibited a limited increase in superoxide dismutase, ascorbate peroxidase, and total peroxidase activity under increasing salinity. These varieties also recorded maximum salt stress-induced damage in terms of increased lipid peroxidation, H₂O₂ content, and electrolyte leakage. On the other hand, CS-52 recorded maximum proline accumulation with minimum levels of H₂O₂, electrolyte leakage, and malondialdehyde contents. With increasing salinity stress, CS-52 recorded maximal increase in the activity of antioxidant enzymes. However, catalase activity did not correlate with alterations in H₂O₂ levels under stress. Interestingly, a lower superoxide dismutase:ascorbate peroxidase ratio in CS-52 correlated with stress tolerance trait, while a comparatively higher superoxide dismutase:ascorbate peroxidase ratio in RLM-198 marked the susceptible nature of the variety. Our results propose that superoxide dismutase:ascorbate peroxidase ratio is the critical factor, determining the degree of stress tolerance in Brassica juncea.     

Brassinosteroid-mediated evaluation of antioxidant system and nitrogen metabolism in two contrasting cultivars of Vigna radiata under different levels of nickel

The role of 28-homobrassinolide (HBL) in countering nickel-induced oxidative damage through overexpression of antioxidant enzymes and proline in Vigna radiata has been investigated. Two varieties of V. radiata, one sensitive to Ni (PDM-139) and the other tolerant to Ni (T-44), were sown in the soil fed with different levels (0, 50, 100 or 150 mg kg⁻¹) of Ni, and at 29-day stage, foliage of plants was applied with deionized water (control), 10⁻⁸ or 10⁻⁶ M of HBL. The plants were sampled at 45-day stage of growth to assess various physiological as well as biochemical characteristics. The remaining plants were allowed to grow up to maturity to study the yield characteristics. The growth traits, leghemoglobin, nitrogen and carbohydrate content in the nodules, leaf chlorophyll content, photosynthesis efficiency, leaf water potential, activities of nitrate reductase, carbonic anhydrase and nitrogenase decreased proportionately with the increasing concentrations of nickel, whereas electrolyte leakage, various antioxidant enzymes viz. catalase, peroxidase and superoxide dismutase and accumulation of proline increased at 45-day stage. However, the exogenously applied HBL to the nickel-stressed or non-stressed plants improved growth, nodulation and photosynthesis and further enhanced the various antioxidant enzymes viz. catalase, peroxidase and superoxide dismutase and accumulation of proline. The deleterious impact of Ni on the plants was concentration dependent where HBL applied to the foliage induced overexpression of antioxidant enzyme and accumulation of proline (osmolyte) which could have conferred tolerance to Ni up to 100 mg kg⁻¹, resulting in improved growth, nodulation, photosynthesis and yield attributes.     

Is proline the quintessential sentinel of plants? A case study of postharvest flower senescence in Dianthus chinensis L.

The present investigation primarily focussed on evaluating the efficacy of exogenous proline on the flower longevity of Dianthus chinensis L. Floral buds were harvested at the paint brush stage (i.e., a day prior to anthesis) and divided into 6 sets, with one set of buds (i.e., control) held in distilled water and rest of the 5 sets were supplemented with various concentrations of proline, viz., 10 mM, 20 mM, 30 mM, 40 mM and 50 mM. The application of proline at 40 mM concentration proved out to be most effective in improving the longevity of the flowers by about 4 days as compared to the control. The ameliorated longevity coincided with enhanced floral diameter, fresh mass, dry mass and water content. The flowers with delayed senescence also maintained higher soluble proteins, sugars and phenols. The results suggest that exogenous proline effectively alleviates oxidative stress in the petal tissue, as evident by a relatively lower maloendialdehyde content, which is manifested in the form of reduced lipid peroxidation (LPO). Reduced LPO was commensurate with increased membrane stability, quantified by membrane stability index. Moreover, the flowers with improved longevity exhibited a decline in lipoxygenase activity and significant augmentation of antioxidant enzymes superoxide dismutase, catalase and ascorbate peroxidase.     

Desiccation induced changes in osmolytes production and the antioxidative defence in the cyanobacterium Anabaena sp. PCC 7120

Cells of Anabaena sp. PCC 7120, a low desiccation tolerant cyanobacterium, was subjected to prolonged desiccation and effect of loss of water was examined on production of osmolytes, and antioxidant response as well as on overall viability in terms of photosynthetic activity. During dehydration (22 h), the organism maintained about 98.5 % loss of cellular water, yet cells remained viable as about 30 % of photosynthetic O₂-evolution activity resumed upon hydrating (1 h) such cells. In desiccated state, cyanobacterial cells accumulated osmolytes within 1 h though their contents decreased thereafter. The highest levels of trehalose (179 nmol mg⁻¹ protein), sucrose (805 nmol mg⁻¹ protein) and proline (23.2 nmol mg⁻¹ protein) were attained within 1 h. Chlorophyll a and carotenoid contents also increased within 1 h but phycocyanin level showed opposite trend. The oxygen-evolving activity declined in desiccated cyanobacterial biomass while rehydration led to instant recovery, indicating that cells protect the photosynthetic machinery against desiccation. Notwithstanding, activities of antioxidant enzymes (catalase, peroxidase and superoxide dismutase) attained their peaks after 3 h of desiccation, though within 10 min of rehydration, their levels returned back close to basal activities of the cultured cells. We propose that onset of osmolyte production in conjunction with upshift of antioxidant enzymes apparently protects the cyanobacterial cells from desiccation stress.     

Elucidating Cd-mediated distinct rhizospheric and in planta ionomic and physio-biochemical responses of two contrasting Zea mays L. cultivars

Cadmium (Cd) in soil–plant system can abridge plant growth by initiating alterations in root zones. Hydroponics and rhizoboxes are useful techniques to monitor plant responses against various natural and/or induced metal stresses. However, soil based studies are considered more appropriate in order to devise efficient food safety and remediation strategies. The present research evaluated the Cd-mediated variations in elemental dynamics of rhizospheric soil together with in planta ionomics and morpho-physio-biochemical traits of two differentially Cd responsive maize cultivars. Cd-sensitive (31P41) and Cd-tolerant (3062) cultivars were grown in pots filled with 0, 20, 40, 60 and 80 µg/kg CdCl₂ supplemented soil. The results depicted that the maize cultivars significantly influenced the elemental dynamics of rhizosphere as well as in planta mineral accumulation under applied Cd stress. The uptake and translocation of N, P, K, Ca, Mg, Zn and Fe from rhizosphere and root cell sap was significantly higher in Cd stressed cv. 3062 as compared to cv. 31P41. In sensitive cultivar (31P41), Cd toxicity resulted in significantly prominent reduction of biomass, leaf area, chlorophyll, carotenoids, protein contents as well as catalase activity in comparison to tolerant one (3062). Analysis of tolerance indexes (TIs) validated that cv. 3062 exhibited advantageous growth and efficient Cd tolerance due to elevated proline, phenolics and activity of antioxidative machinery as compared to cv. 31P41. The cv. 3062 exhibited 54% and 37% less Cd bio-concentration (BCF) and translocation factors (TF), respectively in comparison to cv. 31P41 under highest Cd stress regime. Lower BCF and TF designated a higher Cd stabilization by tolerant cultivar (3062) in rhizospheric zone and its potential use in future remediation plans.     

Plant growth-promoting Bacillus sp. strain SDA-4 confers Cd tolerance by physio-biochemical improvements,better nutrient acquisition and diminished Cd uptake in Spinacia oleracea L.

Cadmium (Cd) is highly toxic metal for plant metabolic processes even in low concentration due to its longer half-life and non-biodegradable nature. The current study was designed to assess the bioremediation potential of a Cd-tolerant phytobeneficial bacterial strain Bacillus sp. SDA-4, isolated, characterized and identified from Chakera wastewater reservoir, Faisalabad, Pakistan, together with spinach (as a test plant) under different Cd regimes. Spinach plants were grown with and without Bacillus sp. SDA-4 inoculation in pots filled with 0, 5 or 10 mg kg⁻¹ CdCl₂-spiked soil. Without Bacillus sp. SDA-4 inoculation, spinach plants exhibited reduction in biomass accumulation, antioxidative enzymes and nutrient retention. However, plants inoculated with Bacillus sp. SDA-4 revealed significantly augmented growth, biomass accumulation and efficiency of antioxidative machinery with concomitant reduction in proline and MDA contents under Cd stress. Furthermore, application of Bacillus sp. SDA-4 assisted the Cd-stressed plants to sustain optimal levels of essential nutrients (N, P, K, Ca and Mg). It was inferred that the characterized Cd-tolerant PGPR strain, Bacillus sp. SDA-4 has a potential to reduce Cd uptake and lipid peroxidation which in turn maintained the optimum balance of nutrients and augmented the growth of Cd-stressed spinach. Analysis of bioconcentration factor (BCF) and translocation factor (TF) revealed that Bacillus sp. SDA-4 inoculation with spinach sequestered Cd in rhizospheric zone. Research outcomes are important for understanding morpho-physio-biochemical attributes of spinach-Bacillus sp. SDA-4 synergy which might provide efficient strategies to decrease Cd retention in edible plants and/or bioremediation of Cd polluted soil colloids.     

Phytotoxicity of green synthesized silver nanoparticles on Camelina sativa L

Due to the increased production and release of silver nanoparticles (AgNPs) in the environment, the concerns about the possibility of toxicity and oxidative damage to plant ecosystems should be considered. In the present study, the effects of different concentrations of AgNPs (0, 0.5, 1, 2, 3 and 4 g/L) synthesized using the extract of camelina (Camelina sativa) leaves on the growth and the biochemical traits of camelina seedlings were investigated. The results showed that AgNPs significantly increased Ag accumulation in the roots and shoots which decreased the growth and photosynthetic pigments of camelina seedlings. The highest decrease in the height and total dry weight was observed by 53.1 and 61.8% under 4 g/L AgNPs, respectively over control plants. AgNPs application over 2 g/L enhanced the accumulation of proline, malondialdehyde, hydrogen peroxide and methylglyoxal, and up-regulated the activity of antioxidant enzymes (superoxide dismutase, catalase, ascorbate peroxidase and glutathione reductase) and glyoxalase (glyoxalase I and II) system which indicates oxidative stress induction in camelina seedlings. Moreover, AgNPs reduced ASA and GSH contents and increased DHA and GSSG contents, hence disrupting the redox balance. These results showed that AgNPs at 4 g/L had the most toxic effects on the camelina growth. Therefore, increasing oxidative stress markers and the activity of antioxidant enzymes and enzymes involved in glyoxalase system indicated the oxidative stress induced by AgNPs treatments over 2 g/L as well as the induction of antioxidant defense systems to combat AgNPs-induced oxidative stress.     

Impact of bio-fertilizers and different levels of cadmium on the growth,biochemical contents and lipid peroxidation of Plantago ovata Forsk

Plantago ovata Forsk. (isabgol) is a valuable medicinal plant; its seeds and shell have a significant role in pharmacy as a laxative compound. Increasing soil contamination with cadmium (Cd) is one of the major concerns and is responsible for toxic effects in plants. This investigation was aimed to analyze the role of biofertilizers in alleviation of cadmium stress, given at the rate of 0, 50, and 100 mg kg⁻¹ of soil. The plants of isabgol, were grown in pots with and without application of AM fungi and Azotobacter (alone and combination). Cadmium showed negative effect on growth and biochemical component whereas proline and MDA content increase with increasing cadmium concentration. Addition of bio-fertilizer showed better growth and higher pigment concentration under cadmium stress as compared to the control. The dual inoculation of AM fungi and Azotobacter was found to be the best in reduction of cadmium stress and promotion of growth parameters.     

The beneficial role of potassium in Cd-induced stress alleviation and growth improvement in Gladiolus grandiflora L.

Heavy metal contaminated agricultural soils are one of the most important constraints for successful cultivation of crops. The current research was conducted to evaluate the role of potassium (K) on plant growth and amelioration of cadmium (Cd) stress in Gladiolus grandiflora under greenhouse conditions. G. grandiflora corms were sown in media contaminated with 0 (C), 50 (Cd50) and 100 (Cd100) mg Cd kg^?1 soil. The plants growing in Cd-contaminated media exhibited reduced gas exchange attributes, chlorophyll (Chl) contents, vegetative and reproductive growth as compared to control. The plants raised in Cd contaminated media showed reduced nutrition yet higher Cd contents. However, supplementation of 60 mg Kg^?1 K in treated plants (C+K, Cd50+K and Cd100+K) improved quantity of total soluble protein and proline (Pro) along with activity of antioxidant enzymes including superoxide dismutase (SOD), catalase (CAT), peroxidase (POD) and ascorbate peroxidase (APX) under Cd stress. Similarly, K supplementation reduced the level of malondialdehyde (MDA) and hydrogen peroxide (H₂O₂) in treated plants. Potassium supplemented plants exhibited better vegetative and reproductive growth. The improved stress tolerance in K supplemented plants was attributed to the reduced quantity of MDA and H₂O₂, enhanced synthesis of protein, proline, phenols, flavonides and improved activity of antioxidant enzymes. The present research supports the application of K for alleviation of Cd stress in G. grandiflora.     

Improving key enzyme activities and quality of rice under various methods of zinc application

Zinc (Zn) is an important micronutrient for the physiology of plants. It is poorly available to the plants in soil solution. A pot experiment was conducted to evaluate effectiveness of various Zn application methods on key enzyme activities and protein content of two contrasting rice genotypes viz., PD16 (Zn efficient) and NDR359 (Zn inefficient). The treatments were, control (0 mg Zn kg⁻¹ soil), soil application (5 mg Zn kg⁻¹ soil), foliar application (0.5 % ZnSO₄ + 0.25 % lime at 30, 60 and 90 days after transplanting), soil (5 mg Zn kg⁻¹ soil) + foliar application of 0.5 % ZnSO₄ + 0.25 % lime at 30, 60 and 90 days after transplanting. Among all the methods tested soil+foliar application of Zn fertilizers was found most effective in increasing superoxide dismutase (SOD) and carbonic anhydrase (CA) activities as well as chlorophyll and protein content in both the rice varieties. NDR359, showed higher enzyme activities and more chlorophyll content in leaves than PD16, when Zn was applied either through foliar spray alone or in soil along with foliar application. Regarding the protein content in grains, PD16 showed higher protein content than NDR359, thus showed better translocation of Zn from leaves to grains.     

Nutrient composition of spent wash and its impact on sugarcane growth and biochemical attributes

Nutrient composition of crude and digested spent wash and effect of their application on sugarcane growth and biochemical attributes were studied. Higher concentrations of essential nutrients (P, S, Fe, Mn, Zn, Cu) and heavy metals (Cd, Cr, Ni and Pb) were present in crude spent wash (CSW) as compared to the digested spent wash (DSW); sulphur content was the highest (765 μg ml⁻¹ in DSW and 1,609 μg ml⁻¹ in CSW) among all nutrients analyzed. Sugarcane (Saccharum spp. hybrid cultivar CoLk 8102) setts grown in soil pot culture conditions with different rates of crude spent wash (5, 10, 20 and 100 ml kg⁻¹ soil) along with digested spent wash (100 ml kg⁻¹ soil) showed improvement in bud sprouting (10.5 %), settling height (40 %), root number (9.4 %), root length (13.2 %), chlorophyll a (52.9 %) and b (55.3 %) contents and activity of catalase (98 %) enzyme over control at low rate of crude spent wash (5 ml kg⁻¹ soil). Whereas, higher doses of spent wash (20 and 100 ml kg⁻¹ soil) decreased these parameters markedly except peroxidase which was found higher at all the levels of both CSW and DSW. Findings indicated stimulatory effect of low rate of crude spent wash (5 ml kg⁻¹ soil) on root and shoot growth and inhibitory effect of higher dose (100 ml kg⁻¹ soil) of both crude and digested spent wash, therefore, judicious application of spent wash will improve crop productivity and alleviate environmental pollution problems.     

Protective role of tebuconazole and trifloxystrobin in wheat (Triticum aestivum L.) under cadmium stress via enhancement of antioxidant defense and glyoxalase systems

Cadmium (Cd) is a toxic metal and an environmental pollutant that significantly reduces plant growth and productivity. Proper management can ameliorate dysfunction and improve the plant growth and productivity exposed to Cd. Therefore, the present study was conducted to explore the protective role of the fungicides tebuconazole (TEB) and trifloxystrobin (TRI) in helping wheat (Triticum aestivum L. cv. Norin 61) seedlings to tolerate Cd. Five-day-old hydroponically grown seedlings were allowed to mild (0.25 mM CdCl₂) and severe (0.5 mM CdCl₂) Cd stress separately and with the fungicides (2.75 µM TEB + 1.0 µM TRI) for the next four days. Compared to control, the level of H₂O₂ in the seedlings exposed to mild and severe Cd stress alone increased by 81 and 112%, respectively. The accumulation of Cd also increased in the wheat seedlings along with declining mineral nutrients under Cd stress. The protective effect of TEB and TRI was observed with the enhancement of the antioxidant defense and methylglyoxalase systems and reduction in oxidative damage. Applying TEB and TRI reduced MDA (by 9 and 18%), EL (by 21 and 17%), MG (by 12 and 17%), and LOX activity (by 37 and 27%), respectively, relative to Cd stress alone. Cadmium uptake also decreased in the shoots (by 48 and 50%, respectively) and roots (by 23 and 25%, respectively) of the fungicide-treated wheat seedlings under mild and severe Cd stress, relative to stress alone. These results indicate the exogenous application of TEB and TRI is a promising approach to improve Cd tolerance in wheat plants. Further investigation is needed under field conditions and for other crop species to determine the Cd-tolerance induced by TEB and TRI application.     

Temperature response of photosynthesis in different drug and fiber varieties of Cannabis sativa L.

The temperature response on gas and water vapour exchange characteristics of three medicinal drug type (HP Mexican, MX and W1) and four industrial fiber type (Felinq 34, Kompolty, Zolo 11 and Zolo 15) varieties of Cannabis sativa, originally from different agro-climatic zones worldwide, were studied. Among the drug type varieties, optimum temperature for photosynthesis (T_opt) was observed in the range of 30–35 °C in high potency Mexican HPM whereas, it was in the range of 25–30 °C in W1. A comparatively lower value (25 °C) for T_opt was observed in MX. Among fiber type varieties, T_opt was around 30 °C in Zolo 11 and Zolo 15 whereas, it was near 25 °C in Felinq 34 and Kompolty. Varieties having higher maximum photosynthesis (P_{N max}) had higher chlorophyll content as compared to those having lower P_{N max}. Differences in water use efficiency (WUE) were also observed within and among the drug and fiber type plants. However, differences became less pronounced at higher temperatures. Both stomatal and mesophyll components seem to be responsible for the temperature dependence of photosynthesis (P_N) in this species, however, their magnitude varied with the variety. In general, a two fold increase in dark respiration with increase in temperature (from 20 °C to 40 °C) was observed in all the varieties. However, a greater increase was associated with the variety having higher rate of photosynthesis, indicating a strong association between photosynthetic and respiratory rates. The results provide a valuable indication regarding variations in temperature dependence of P_N in different varieties of Cannabis sativa L.     

Influence of silicon and chitosan on growth and physiological attributes of maize in a saline field

Soil salinity is the main constraint for crop productivity in many parts of the world. Application of silicon (Si) and chitosan (Chi) can improve crop growth under saline soil conditions. The current study was aimed to examine the effects of Si and Chi on mitigation of salinity, morphological and physiological attributes as well as the antioxidant system of maize (Zea mays L.) under saline soil conditions. A field experiment was conducted that comprised of nine treatments as follows: (i) Control (no amendment), (ii) Silicon 40 kg ha⁻¹ (Si1), (iii) Chitosan 15 kg ha⁻¹ (Chi1), (iv) Si1 + Chi1, (v) Silicon 80 kg ha⁻¹ (Si2), (vi) Chitosan 30 kg ha⁻¹ (Chi2), (vii) Si2 + Chi2, (viii) Si1 + Chi2 and (ix) Si2 + Chi1. Application of Si and Chi substantially improved the morphological and physiological attributes as well as antioxidant enzymes such as superoxide dismutase (SOD), peroxidase (POD) and catalase (CAT) of maize plants, and combined application of Si and Chi was more effective when compared with Si and Chi treatments separately. Membrane stability index was improved by 25%, relative water content by 26%, chlorophyll a by 69% and b by 56% with combined application of Si and chitosan (Si2 + Chi2) compared with control. The SOD, POD and CAT increased by 36%, 38% and 65% with Si2 + Chi2 compared with control. The results suggest that Si and Chi application is the possible option for alleviating salinity stress in maize plant. Further research is suggested to examine Si and Chi effects on various crop''s growth.     

Metabolic changes associated with vernalization of wheat. I. Carbohydrate and nitrogen patterns

A spring wheat (Triticum aestivum) and an obligate winter wheat (Triticum compactum) variety were each grown for 5 weeks in controlled environments at 2° and 25°. The threshold for flower induction in the winter wheat was 4 to 5 weeks at 2°, whereas the spring wheat had no low temperature requirement for flowering. Changes in the levels of carbohydrate and nitrogen fractions in the wheat leaves were determined during their growth in the cold and warm environments. There was an enhanced accumulation of the 5 carbohydrate fractions in both wheat varieties grown at 2° compared to 25°. Highly significant differences in the levels of sucrose, oligosaccharides, and starch were found between the spring and winter varieties grown at 2°. The winter wheat seedlings grown at 2° accumulated much more of these carbohydrates than the corresponding spring wheat. The carbohydrate patterns in both varieties grown at 25° were nearly identical except for the final 2 weeks of growth.

The level of nitrogenous substances in the tissues grown at 2° was much higher than in the corresponding tissues grown at 25°. The only significant difference between the spring and winter varieties was in the soluble protein fraction. This fraction rose nearly 3-fold in the winter variety grown at 2°, whereas it remained nearly constant in the similarly grown spring wheat. Most of the changing chemical patterns observed in relation to the vernalization treatment appear to be metabolic alterations associated with low temperature rather than alterations directly related with the vernalization response.