Resumo em Inglês:
Differential antioxidative activities were assessed in the leaves of two maize inbreds (A-180 and A-619) under salt stress and the subsequent recovery period. Total antioxidation test revealed that in both inbreds, this ability was sharply increased during stress period, but was slowly reverted back to the normal level during recovery. The enzymatic antioxidative analysis showed differential patterns in the activities of catalase, peroxidase and polyphenol oxidase in both maize inbreeds. Comparative analysis of the activity of phenylalanine ammonia lyase (PAL), a key enzyme at the gateway of propanoid biosynthetic pathway, suggested that propanoid compounds might be antioxidants of pivotal importance to the salt-challenged maize antioxidation system. As for drought-stressed plants, a PAL-dependent antioxidative strategy is proposed as a promising target for maize salt resistance engineering.Resumo em Português:
Erythrina velutina Willd. (comumente chamada mulungu) é uma espécie decídua, heliófita, encontrada nas regiões semi-áridas do Nordeste do Brasil. Com o objetivo de avaliar o crescimento e as relações hídricas de mudas de mulungu cultivadas em solo com diferentes graus de umidade, foi desenvolvido um experimento em condições de casa de vegetação utilizando quatro tratamentos hídricos (100%, 75%, 50% e 25% da capacidade de campo- CC). Foram avaliados o potencial hídrico foliar antes do amanhecer (Ψpdw) e ao meio-dia (Ψmdw), o teor relativo de água (TRA), altura das plantas, número de folhas, diâmetro do caule, área foliar (AF), área foliar específica (AFE), razão de área foliar (RAF), matéria seca para os diversos órgãos, partição de biomassa e relação raiz/ parte aérea. Não foram encontradas diferenças significativas para Ψpdw após 30 dias; Entretanto, ao meio-dia, as plantas controle e aquelas sob 75% CC sofreram uma maior redução no Ψmdw do que as plantas cultivadas com 50% e 25% CC. Após 90 dias, apenas as plantas sob 50% CC exibiram reduções no Ψmdw. O TRA foi reduzido ao meio-dia, mas não foram observadas diferenças entre os tratamentos. O déficit hídrico reduziu quase todos os parâmetros de crescimento, especialmente nas plantas cultivadas com 25% CC, como observado para o número de folhas, diâmetro do caule, altura das plantas, AF, AFE e matéria seca para os diversos órgãos. A RAF e a razão raiz/parte aérea não foram afetadas. O mulungu na fase de muda parece ter desenvolvido rusticidade para superar períodos de seca, sem modificar o padrão de distribuição de matéria seca. A manutenção da pressão de turgescência parece estar mais associada a redução nas taxas de crescimento do que a redução do potencial hídrico foliar.Resumo em Inglês:
Erythrina velutina Willd. (common name: mulungu) is a deciduous, heliophyte found in the semi-arid region of northeastern Brazil. To evaluate the growth and water relations of mulungu seedlings in soils with different degrees of moisture content, an experiment was carried out under greenhouse conditions using four water treatments (100%, 75%, 50% and 25% of the field capacity- FC). Predawn (Ψpdw) and midday leaf water potential (Ψmdw), relative water content (RWC), plant height, number of leaves, stem diameter, leaf area (LA), specific leaf area (SLA), leaf area ratio (LAR), dry matter in different organs, biomass partitioning and root:shoot ratio were evaluated. No differences were detected between treatments for Ψpdw after 30 days; however, at midday, control plants and those under 75% FC underwent a greater reduction in Ψmdw than plants cultivated with 50% and 25% FC. After 90 days, only the plants under 50% FC exhibited a reduction in Ψmdw. RWC was reduced at midday, but there were no differences between treatments. Nearly all growth parameters were reduced due to water deficit, especially in the plants with 25% FC, as determined by the number of leaves, stem diameter, plant height, LA, SLA and dry mass in several organs. LAR and root:shoot ratio were not affected. Mulungu seedlings seem to have developed rusticity to overcome intermittent droughts with no change in the pattern of dry matter distribution. The maintenance of turgor pressure seems to be more associated to a reduction in the growth ratio than a reduction in leaf water potential.Resumo em Inglês:
Experiments were conducted to evaluate the plant tolerance to Fe and its phytotranslocation by Jatropha curcas L. from an iron rich wasteland soil. The soil was collected from wasteland soil (WLS) of a small town Sandila, (Hardoi, U.P.) India, and three Jatropha clones were cultivated in WLS amended or not with sand or cowdung in a ratio of 3:2. The WLS had high pH, elevated electric conductivity (EC) and was rich in organic carbon and total NPK. Iron and Mn were 2-3 folds higher than that in the normal field soil. Net root and shoot elongation as well as fresh and dry biomass of the plants were only slightly affected at 100 d in WLS as compared with that grown in non-polluted soil. Tolerance index (TI) of J. curcas was significantly higher in cowdung amended WLS in comparison to that in WLS, or WLS amended with sand. Translocation factor (TF) from the soil to plants for Fe was significantly higher in WLS than that in the normal field soil. Bio-concentration factor (BCF) and concentration index (CI) for Fe were 0.12 to 0.37, 1.0 to 6.2 respectively. The results indicate that Jatropha plantation is suitable for phytoremediation of Fe-contaminate wasteland soils, and also that these polluted fields could be used to cultivate this important biodiesel plant species.Resumo em Português:
A dinâmica fotossintética da espécie pioneira tropical Byrsonima sericea DC. foi estudada durante o processo de regeneração de uma mata nativa por avaliações ecofisiológicas (trocas gasosas, fluorescência da clorofila a e conteúdo de pigmentos fotossintéticos) e parâmetros anatômicos das plantas em ambientes ensolarados e sombreados. As avaliações ecofisiológicas foram feitas mensalmente por um ano e os dados foram agrupados em estação seca e chuvosa. Byrsonima sericea DC. apresentou plasticidade anatômica que a capacita a se estabelecer em ambientes com contrastantes condições luminosas. Nas condições ensolaradas, ela produz lâmina foliar mais espessa (cerca de 420 µm) e epiderme adaxial plana, enquanto em ambientes sombreados, as folhas apresentaram a epiderme convexa e lâmina mais delgada (cerca de 393 µm). Não foram encontradas diferenças significativas na composição de pigmentos em função do ambiente, no entanto, durante a estação seca, as plantas apresentaram concentrações significativamente maiores de pigmentos fotossintéticos. As plantas de ambientes ensolarados mostraram diminuição na razão Fv/ FO (na estação chuvosa) e NPQ (na estação seca), mas não foram observadas diferenças entre as plantas de sol ou sombra numa mesma estação do ano. Taxas fotossintéticas significativamente maiores foram encontradas na estação chuvosa para as plantas de sol quando comparadas com as plantas de sombra (9.9±0.8 e 7.4±0.3 µmol m-2s-1, respectivamente). Aumento significativo na transpiração foi observado em plantas de sombra durante a estação seca, mas sem afetar a eficiência no uso da água. Dados ecofisiológicos sugerem que, principalmente as plantas mais expostas ao sol sofreram limitações hídricas durante a estação seca e que, na estação chuvosa, estas plantas aumentaram sua taxa fotossintética. Isso possivelmente foi devido a maior força de dreno resultante do maior crescimento neste período. Os dados sugerem que alterações anatômicas, especialmente a epiderme adaxial convexa, estariam auxiliando na captação de luz nas plantas sombreadas durante ambas as estações, prevenindo alterações nos pigmentos, como o aumento de clorofila b geralmente observado em plantas de sombra, mas não detectado no presente estudo. Outra conseqüência da maior quantidade de luz capturada por estas plantas de sombra foi que, durante a estação seca sua taxa fotossintética não diferiu da das planas de ambientes ensolarados. No entanto, quando a água não foi um fator limitante, um melhor desempenho fotossintético foi observado nesta espécie pioneira, em ambientes abertos.Resumo em Inglês:
The photosynthetic dynamics of the tropical pioneer species, Byrsonima sericea DC., were studied during the regeneration process of a native forest by evaluating ecophysiological (gas exchange, chlorophyll a fluorescence and photosynthetic pigment contents) and anatomical parameters of plants in sunny and shady environments. Ecophysiological evaluations were carried out monthly for one year, encompassing both a dry and a rainy season. Byrsonima sericea DC. presents anatomical plasticity that enables it to establish in environments with contrasting light regimes. In sunny conditions, it produced a thicker leaf (about 420 mm) and flat adaxial epidermis, whilst in the shade, leaves had a thinner convex adaxial epidermis (about 395 mm). No differences were found in the compositions of the pigments in the different environments, however, during the dry season, the plants presented a significantly higher concentration of photosynthetic pigments. In the sun, plants showed decreases in Fv/F0 ratio (in the rainy season) and NPQ (in the dry season), but no difference was observed between plants that were in the sun or in the shade. A significantly higher net photosynthetic rate was found only in the rainy season in the plants in the sun, compared to shaded plants (9.9±0.8 and 7.4±0.3 µmol m-2s-1, respectively). Significant increase in transpiration was observed in plants in the shade during the dry season, but no alterations were observed in the water use efficiency. Ecophysiological data suggest that mainly plants overexposed to the sun underwent water limitations during the dry season and that, in the rainy season, these plants increased their net photosynthetic rate, possibly due to the greater drainage force resulting from increased growth during this period. Data suggest that anatomic alterations, namely the convex adaxial epidermis, could aid in the supply of light to shaded plants during both seasons, precluding changes in the pigments, such as the increase in chlorophyll b usually observed in shaded plants, but not detected in the present study. Another consequence of the greater quantity of light captured by these shade plants is that during the dry season their net photosynthetic rate was not different from that of plants in a sunny environment. However, when water was not a limiting factor, a better photosynthetic performance was observed in this pioneer specie in open spaces.Resumo em Inglês:
Ashwagandha, commonly known as the Indian Ginseng (Withania somnifera) is an ingredient in many herbal preparations used for healing various ailments. It is cultivated in semi-arid regions of India as rain-fed crop. The response of this crop (cv. JA-134) to progressive soil moisture deficit on growth, physiology and content of phytochemicals was studied. At the end of treatment period, soil water potential (Ψw) decreased to -10.93, -1.15 MPa at 30 cm depth, predawn leaf water potentials were reduced to -0.62 and -0.51 MPa in the severe and moderate stress. Leaf area was reduced by 27.4% and 34.4% in moderate and severe water stress treatment compared to control. Chlorophyll content was reduced by 60% in the severe water stress. Changes in the steroidal alkaloids and lactones that are the major medicinal active principles derived from root extracts of this plant species was also analyzed. A reduction of 52.6% in net photosynthesis was noticed under severe stress. At the end of the treatment period, moderate and severe stress treatments had 0.751 and 0.714 mg g-1 12-deoxywithastramonolide (12-DWS) content in the roots respectively. The content of 12-DWS and withanolide were at 77% and 93% of the control in the moderate and severe stress, respectively, while yield of these compounds were at 65% and 78% of control in mild and severe stress. Thus, preferential partitioning of biomass in roots leads to higher root yield in moderate stress. Higher root yield partially offset the loss of bioactive compounds under soil moisture stress.Resumo em Inglês:
The present study determined the effects of copper and chromium metals on the endogenous titers of polyamines, auxins, abscisic acid and antioxidative enzyme activities in Raphanus sativus L. cv. Pusa chetki seedlings. Among polyamines, putrescine and spermidine contents were enhanced by Cu2+ metal to 62.44 and 402.8 µg g-1 f.w. respectively over control. Spermine which was not observed in control was recorded in highest concentration (1287.9 µg g-1 f.w.) in Cu2+ metal stressed seedlings. On the other hand Cr6+ metal treated seedlings showed reduced contents of putrescine (1.43 µg g-1 f.w.), cadaverine (0.09 µg g-1 f.w.), spermidine (277.99 µg g-1 f.w.) and spermine (2.29 µg g-1 f.w.) when compared to control and Cu2+ metal treated seedlings. Significant decline in free and bound IAA concentration were found under Cu2+ and Cr6+ metal stress when compared to control. Naphthalene acetic acid not recorded in control seedlings was detected in seedlings treated with Cu2+ and Cr6+ metal. Activities of guaiacol peroxidase and catalase were reduced significantly under Cu2+ and Cr6+ metal stress in comparison to control. Superoxide dismutase activity enhanced significantly under Cr6+ rather than Cu2+ metal treatment. In addition the phytotoxicity of Cu2+ and Cr6+ metal on seedling growth was also determined. The data suggest that Cr6+ is more phytotoxic than exposure to Cu2+ metal.Resumo em Inglês:
The present study investigates the effect of long and short term Cd stress in chickpea plants and evaluates the protective effect of exogenous nitric oxide (NO) supplementation using sodium nitroprusside (SNP). Cadmium treatments were given before sowing (long term stress) and thirty days after germination (short term stress). Sodium nitroprusside was given as foliar spray 30 days after germination to both long and short term Cd treated plants. Cadmium adversely affected the membranes as was evident from increased electrolyte leakage and lipid peroxidation levels. Sodium nitroprusside treatments decreased ion leakage and lipid peroxidation levels significantly. Short term Cd stress resulted in a higher induction of the catalase, peroxidase, ascorbate peroxidase, glutathione reductase and superoxide dismutase as compared to long term Cd stress. Nitric oxide showed its positive effect by further increasing the activities of antioxidant enzymes. Cadmium stress also altered the level of antioxidant metabolites by reducing the ascorbate redox ratio (ASC/DHA) and glutathione redox ratio (GSH/GSSG). Sodium nitroprusside treatments increased the redox ratios. Cadmium also adversely affected the seed yield and a greater decline was observed with long term Cd stress as compared to short term Cd stress. Nitric oxide had a positive effect on seed yield and Cd accumulation. The study concludes that an exogenous supply of NO protects chickpea plants from Cd toxicity.Resumo em Inglês:
The present work was aimed at testing the hypothesis that mycorrhizal Prosopis alba, an economically important tree species worldwide, presents increased salt-tolerance compared with non-mycorrhizal ones and at gaining insight into the possible mechanisms underlying that improvement. For this purpose, a randomized complete block experiment with two factors: mycorrhizal treatments with or without the arbuscular fungus Glomus intraradices and two salinity levels, 0 and 200 mM NaCl was performed. Plant growth in P. alba plants colonized by G. intraradices was less affected by salinity than that in non-arbuscular mycorrhizal (AM) plants, indicating that mycorrhizal colonization turned P. alba more tolerant to salinity. Photosynthesis was reduced by salinity in non-AM plants but not in AM ones. Salini ty caused a significant decrease in mean stomatal conductance and transpiration rate, in mycorrhizal plants, but not in uninoculated ones. In this work, we detected two main mechanisms intervening in the salt tolerance enhancement of P. alba by the inoculation with G. intraradices: a- maintaining the net photosynthesis level and b- control of the transpiration rate. Taken together, the results suggest that inoculation with G. intraradices improves P. alba survival rates during the implantation period and seems to be a promising strategy to improve P. alba cultivation in saline lands.