Oxidative stress biomarkers and metabolic changes associated with cadmium stress in hyacinth bean (Lablab Purpureus)

Cadmium (Cd)-induced stress in hyacinth bean (Lablab purpureus) was investigated by growing seedlings in a nutrient solution containing increasing cadmium concentrations (0 to 50 μM), under strictly controlled growth conditions. Changes consequent to Cd uptake in growth parameters, enzyme activities and other stress response factors directly or indirectly are related to the cellular free radical scavenging systems. Antioxidants and other stress response components were studied in roots and leaves of 10-day old seedlings over 72 h of exposure. A significant decrease in length, relative water content (RWC), weight of shoot and root, and chlorophyll content was observed in seedlings growing on >10 μM CdCl2. Oxidative stress markers, H2O2, malondialdehyde, proline and total soluble sugars were elevated in both leaves and roots. Ascorbate and phenol contents increased in leaves, but, decreased in roots. Reduced glutathione levels declined in both tissues. Cd stress enhanced antioxidant enzymes, guaiacol peroxidase, glutathione reductase, ascorbate peroxidase and polyphenol oxidase in concentration and time dependent manner in leaves. Antioxidant enzymes in roots showed inverse relationship with concentration and time of exposure. Catalase activity was found to decrease in both leaves and roots. Metabolic enzymes β-amylase and acid phosphatase activity increased in both leaves and roots. The results suggest that primary antioxidative response originates from leaves of Hyacinth bean even though roots are involved in direct uptake of heavy metals. The root tends to accumulate Cd and thus excludes its uptake by leaves.Keywords: Antioxidants, antioxidant enzymes, cadmium, Hyacinth bean.African Journal of Biotechnology Vol. 12(29), pp. 4670-468

Induction of thermotolerance through heat acclimation in lablab bean (Dolichos lablab)

The acclimation of plants to moderately high temperature plays an important role in inducing plant tolerance to subsequent lethal temperatures. This study was performed to investigate the effects of heat acclimation and sudden heat stress on the antioxidant and metabolic profile of lablab bean (Dolichos lablab). Following separate pretreatments with heat acclimation (35°C) and NaCl (100 mM), seedlings of lablab bean were exposed to heat stress at 45°C for 5 h and then recovered at 25°C for five days. Pretreated seedlings performed better under heat stress than the control and it could be associated with the observed increased levels of sugars, proline, glutathione and ascorbate; and increased activities of Peroxidase (POX), glutathione reductase (GR) and ascorbate peroxidase (APX) than just heat shocked seedlings. Seedling growth was dramatically reduced under heat stress but heat acclimation and NaCl pre-treatment were effective in imparting thermoprotection against the lethal heat shock.Keywords: Acclimation, antioxidants, catalase, Dolichos lablab, glutathione reductase, heat stress, peroxidase, proline, sugar.African Journal of Biotechnology Vol. 12(38), pp. 5695-570

Induction of thermotolerance through heat acclimation in lablab bean (Dolichos lablab)

The acclimation of plants to moderately high temperature plays an important role in inducing plant tolerance to subsequent lethal temperatures. This study was performed to investigate the effects of heat acclimation and sudden heat stress on the antioxidant and metabolic profile of lablab bean (Dolichos lablab). Following separate pretreatments with heat acclimation (35°C) and NaCl (100 mM), seedlings of lablab bean were exposed to heat stress at 45°C for 5 h and then recovered at 25°C for five days. Pretreated seedlings performed better under heat stress than the control and it could be associated with the observed increased levels of sugars, proline, glutathione and ascorbate; and increased activities of Peroxidase (POX), glutathione reductase (GR) and ascorbate peroxidase (APX) than just heat shocked seedlings. Seedling growth was dramatically reduced under heat stress but heat acclimation and NaCl pre-treatment were effective in imparting thermoprotection against the lethal heat shock.Keywords: Acclimation, antioxidants, catalase, Dolichos lablab, glutathione reductase, heat stress, peroxidase, proline, sugar.African Journal of Biotechnology Vol. 12(38), pp. 5695-570

Induction of oxidative stress and antioxidative mechanisms in hyacinth bean under zinc stress

Zinc toxicity to plants occurs in soils contaminated by mining and smelting activities, in agricultural soils treated with sewage sludge, and in urban and peri-urban soils enriched by anthropogenic inputs of Zn. Zinc-induced stress in Hyacinth bean ( Lablab purpureus ) was investigated by growing seedlings in hydroponics, supplemented with Zinc (0-600 µM), under controlled growth conditions. Changes in growth parameters, enzyme activities and other stress response factors, as a function of Zn uptake are directly or indirectly related to the cellular free radical scavenging systems. These parameters were studied in 10-day old Lablab seedlings over 72 h of exposure. Relative to leaves, roots accumulated ~12-fold higher amounts of Zn. Oxidative stress markers, H2O2, malondialdehyde, ascorbate, proline, soluble sugars, putrescine and spermidine were elevated in both tissues, whereas, glutathione and spermine levels showed a steady decline. Total phenol increased in roots, but decreased in leaves. Zn-stress enhanced antioxidant enzymes, guaiacol peroxidase, glutathione reductase, and polyphenol oxidase in concentration and time dependent manner in leaves, but showed an inverse relationship in roots. Catalase decreased in both leaves and roots. Metabolic enzymes β-amylase and acid phosphatase increased in both tissues. Invertase increased in leaves but declined drastically in roots. The results suggest that primary antioxidative response originates in leaves of Lablab, while roots are involved in direct uptake of heavy metals and are not adept in extrusion. Also, lower concentrations of Zn (up to 100 µM) stimulate growth of Lablab, but higher concentrations proved detrimental to the plant.Les effets toxiques du Zinc aux cultures se produit dans des sols contaminés par des activités d’exploitation et extraction, dans des sols avec dépots d’égouts, et en sols urbains et peri-urbains enrichis en depots anthropogéniques riches en Zn. Une recherche sur le stress dû au zinc était effectuée sur des plantules du Hyacinth ( Lablab purpureus ) en conditions hydroponiques avec supplément du Zinc (0-600 mM) en conditions de croissance controllée. Les changements des paramètres de croissance, des activités enzymatiques et autres facteurs de réaction au stress, par suite de l’importation du Zinc sont directement ou indirectement en rapport avec des systèmes radicaux cellulaires de fouille libre. Ces paramètres étaient étudiés sur des plantules de Lablab de 10 jours exposées pendant 72 heures. En comparaison avec les feuilles, les raciness ont accumulé 12 fois plus le contenu en Zn. Les marqueurs oxydatifs de stress, H2O2, la malondialdehyde, l’ascorbate, la proline, les sucres solubles, la putrescine et la spermidine étaient élevés dans les tissus, alors que les niveaux de la glutathione et la spermine ont montré une baisse continue. Le phenol total a augmenté dans les raciness, mais décru dans les feuilles. Le stress dû au Zinc a accru la concentration d’enzymes antioxydants, le peroxidase guaiacol, le reductase glutathione, et l’oxidase polyphenol dans les feuilles, mais a montré une relation inverse dans les racines. Par ailleurs, le catalase a décru dans les feuilles et racines. Les enzymes métaboliques b-amylase et le phosphatase acide ont augmenté dans les tissus, tandis que l’invertase a augmenté dans les feuilles et décru drastiquement dans les racines. Les résultats ont suggéré que la réaction antioxydante primaire provient des feuilles de Lablab, pendant que les racines sont impliquées dans des exportations directes des métaux lourds et ne sont pas sujettes à l’ extrusion. Aussi, des plus basses concentrations du Zn (jusqu’100mM) ont stimulé la croissance du lablab pendant que des concentrations les plus élevées ont induit des effets nuisibles à la proline de la plante

Specific and non-specific responses of Hyacinth bean (<i style="">Dolichos lablab)</i> to drought stress

130-139Drought and salinity stress are the major causes of historic and modern agricultural productivity losses throughout the world. The availability of irrigation water is a challenge for many countries that have scarce water resources, yet are highly dependent on agriculture as a means of revenue. Effect of drought on Hyacinth bean, Dolichos lablab (HA-4 cultivar) was evaluated in 10-d-old seedlings for 8 d after withholding water. The stress reduced dry and fresh weight, leaf number, surface area, root and shoot length, total chlorophyll and relative water content. Oxidative stress markers, H2O2, glutathione, malondialdehyde, proline, ascorbic acid, total phenols, and total soluble sugars were significantly elevated. Drought enhanced antioxidant enzymes, peroxidase and glutathione reductase, and reduced catalase in a time dependent manner in the leaves. POX and CAT in roots showed inverse relationship with the duration of stress, whereas GR exhibited increased activity. The metabolic activitiy of enzymes, β-amylase and acid phosphatase, increased temporally in leaves and roots. Intensity of isozymes correlated with in vitro levels under stress. The plant showed ability to rehydrate and grow upon re-watering, and levels of antioxidant components correlated with drought tolerance of the plan