Research into nanotechnology, an emerging science, has advanced in almost all fields of technology. The aim of the present study was to evaluate the role of nano-silicon dioxide (nano-SiO2 ) in plant resistance to salt stress through improvement of the antioxidant system of squash (Cucurbita pepo L. cv. white bush marrow). Seeds treated with NaCl showed reduced germination percentage, vigor, length, and fresh and dry weights of the roots and shoots. However, nano-SiO2 improved seed germination and growth characteristics by reducing malondialdehyde and hydrogen peroxide levels as well as electrolyte leakage. In addition, application of nano-SiO2 reduced chlorophyll degradation and enhanced the net photosynthetic rate (Pn ), stomatal conductance (gs ), transpiration rate, and water use efficiency. The increase in plant germination and growth characteristics through application of nano-SiO2 might reflect a reduction in oxidative damage as a result of the expression of antioxidant enzymes, such as catalase, peroxidase, superoxide dismutase, glutathione reductase, and ascorbate peroxidase. These results indicate that nano-SiO2 may improve defense mechanisms of plants against salt stress toxicity by augmenting the Pn , gs , transpiration rate, water use efficiency, total chlorophyll, proline, and carbonic anhydrase activity in the leaves of plants.

Pot experiments were conducted to investigate the probable beneficial role of the individual as well as combined application of kinetin (50 μM Kn) and spermidine (200 μM Spd) on Vigna angularis under cadmium (Cd) stress. Cd treatment reduced growth by declining the content of chlorophylls and carotenoids, photosynthesis, and gas exchange parameters. Exogenously, Kn and Spd application enhanced the photosynthetic parameters and up-regulated the antioxidant system by improving the activities of antioxidant enzymes and the content of non-enzymatic components. In addition, the application of Kn and Spd resulted in significant improvement in the content of sugars, proline, and glycine betaine, ameliorating the decline in relative water content. Oxidative stress parameters including hydrogen peroxide, superoxide, lipid peroxidation, lipoxygenase activity, and electrolyte leakage increased due to Cd stress; however, the application of Kn and Spd imparted a significant decline in all these parameters. Further, reduced Cd uptake was also observed due to Kn and Spd application. Total phenols and flavonoids also increased due to Kn and Spd treatments under normal as well as Cd stress conditions, which may have further helped with the elimination of reactive oxygen species. Reduction in the activity of nitrate reductase and the content of nitrogen was ameliorated due to the exogenous application of Kn and Spd. Therefore, the exogenous application of Kn and Spd benefited Vigna angularis counteracting the damaging effects of Cd stress by up-regulating the tolerance mechanisms, including antioxidant and osmolyte metabolism.

-(Morpho-anatomical effects of sodium azide and nitrous acid on Citrullus lanatus (Thunb.) Matsum. & Nakai (Cucurbitaceae) and Moringa oleifera Lam. (Moringaceae) ). Chemical mutagens (e.g. sodium azide and nitrous acid) are important tools in crop improvements because they produce resistance against pathogens in crops to improve their yield and quality traits. This study investigates the morphological and anatomical effects of sodium azide and nitrous acid on Citrullus lanatus and Moringa olefeira at various concentrations (1 mM, 2 mM, 3 mM and 4 mM) for 4 hours, and planted in plastic pots for 12 weeks observations. Results showed that sodium azide and nitrous acid have differential infl uenced on morphological features (stem height, leaf number and root length) in C. lanatus and M. olefeira respectively. Anatomical features (stomatal density, index and size) are more infl uenced by the sodium azide-treated plants in both plants than in the nitrous acid-treated plants. Both mutagens are more effective in the two plants than the control. Keywords: chemical mutagens, leaf, leaf anatomy, morphology, root, stem RESUMO -(Efeitos morfo-anatômicos da azida sódica e ácido nitroso em Citrullus lanatus (Thunb.) Matsum. & Nakai (Cucurbitaceae) e Moringa oleifera Lam. (Moringaceae)). Os agentes mutagénicos químicos (por exemplo, azida de sódio e ácido nitroso) são ferramentas importantes na melhoria das culturas porque produzem resistência contra patogénios nas culturas para melhorar as suas características de rendimento e qualidade. Este estudo investiga os efeitos morfológicos e anatômicos da azida sódica e do ácido nitroso em Citrullus lanatus e Moringa olefeira em várias concentrações (1 mM, 2 mM, 3 mM e 4 mM) por 4 horas, e plantados em vasos plásticos para observações de 12 semanas. Os resultados mostraram que a azida sódica e o ácido nitroso têm infl uência diferencial nas características morfológicas (altura do caule, número de folhas e comprimento da raiz) em C. lanatus e M. olefeira, respectivamente. Características anatômicas (densidade, índice e tamanho dos estômatos) são mais infl uenciadas pelas plantas tratadas com azida de sódio em ambas as plantas do que nas plantas tratadas com ácido nitroso. Ambos os mutagênicos são mais efi cazes nas duas plantas que o controle.

Dry scarified seeds of Datura innoxia Linn. were gamma-irradiated with 5, 10, 20, 40, 60 and 80 Gy radiation, using a cobalt-60 source at the rate of 0.623 Gy min -1 at room temperature, and germinated on MS-medium in a growth chamber under controlled conditions. Exposure to low dose(s) of radiation (5 Gy) caused stimulatory effect on seed germination. Analysis of 90-dayold seedlings revealed that growth rate of root and shoot, net photosynthetic rate (P N ), stomatal conductance (gs) and the chlorophyll and carotenoid contents increased with 5 Gy radiations. Higher doses proved inhibitory for all the above parameters; the decline observed was positively correlated with increase in intensity of gamma radiation. Intercellular CO 2 (Ci), on the other hand, showed an opposite trend, being lower with 5 Gy than in the control, but significantly higher with increased radiation doses. Hyoscyamine, a tropane alkaloid, exhibited only irregular and non-significant variation in its content, with no perceptible change in structure, in the treated material, indicating that gamma-irradiation caused no significant alteration in the quantity or quality of the compound.

Two concentrations (10-5M and 10-3M) of both GA3 and 2,4-D were used as foliar spray to evaluate the response of date palm (Phoenix dactylifera L.) cv. Khedri seedlings. They affected some of the anatomical characteristics of the first leaf emerging after the beginning of the spray. The high concentration of GA3 increased the size of the midrib and its vascular bundle numbers. Both low and high concentrations of 2,4-D inhibited the formation of the midrib. 2,4-D in both low and high concentrations decreased the number of vessels in both protoxylem and metaxylem and also decreased their diameters, where as GA3 in low and high concentrations have less effect on the number of vessels and its diameters. GA3 in high concentration increased the number of vascular bundles in 1mm long of the leaf blade, while 2,4-D in low and high concentrations decreased their numbers. 10-3M of 2,4-D increased the size and layers of special hypodermal cells.