B. K. Dube

Detrimental Effects of Lead Phytotoxicity on Growth, Yield, and Metabolism of Rice

Abstract To elucidate the deleterious effects of excessive lead (Pb) on rice (Oryza sativa) cv. Swarn Mansoori, plants were grown in refined sand in complete nutrient solution for 42 days. On the 43rd day, Pb nitrate was superimposed at 1 mM (to rice) for 104 days (till harvest). A set of plants in complete nutrient solution was maintained as control for the same period. Excess Pb reduced the dry weight pronouncedly at harvest (after 104 days of metal supply) when the grain yield also decreased. Lead accumulation reduced the concentrations of chlorophyll in leaves, carotene, sugars, phenols, nonprotein nitrogen, protein, iron, manganese, copper, zinc, Hill reaction activity, and peroxidase activity (one of the anti-oxidative enzymes), but increased the concentrations of sulphur, phosphorus, magnesium (early stage) protein nitrogen, and activity of catalase, acid phosphatase, and ribonuclease in leaves of rice. Except for slight growth depression and reduction in number and size of leaves, tillers and inflorescence, no other visible symptoms of excessive Pb could be seen before harvesting.

Cobalt Toxicity Effects on Growth and Metabolism of Tomato

Tomato (Lycopersicon esculentum) cv. Pusa ruby was grown in refined sand with complete nutrition (control) and at 0.05, 0.1, 0.2, 0.4, and 0.5 mM of cobalt sulfate. Visible effects of excess cobalt (Co) manifested on tomato at 0.5 mM Co, after 3 days of metal supply to 40 day old plants. The symptoms of excess cobalt diffused chlorosis of young leaves from base and later necrotic spots appeared on chlorotic areas. The necrotic spots enlarged in size, coalesced and in due coarse most of the entire leaf turned necrotic and withered. With excess Co, there was loss of lamina and marginal scorching of affected leaves. The affected leaves were distorted and appeared hook like with rudimentary leaflets at the top. These effects were most severe at 0.5 mM and the intensity of symptoms gradually diminished with a decrease in Co supply from 0.5 to 0.05 mM. At the latter level of Co, no visible effects could be seen except for growth depression. Excess Co restricted the biomass, concentration of phosphorus (P), sulfur (S), and iron (Fe), chlorophyll a and b, DNA and RNA, reducing and non-reducing sugars, starch, total soluble proteins, protein and non-protein nitrogen, and increased phenol and Co concentrations. In excess Co treated tomato leaves, the activity of catalase decreased and peroxidase, ribonuclease, and acid phosphatase increased. The accumulation of Co was greatest in roots and old leaves and lowest in stem of tomato.

Copper Stress Affects Metabolism and Reproductive Yield of Chickpea

ABSTRACT To observe the effects of copper (Cu) deficiency on growth, metabolism, and reproductive yield of chickpea (Cicer arietinum L.) cv. ‘13.G-256’, plants were grown in refined sand at deficient (0.1 μM) and adequate Cu (1 μM), supplied as copper sulfate (CuSO4·5H2O). At d 35–40, at deficient Cu, the growth of plants were depressed and the young leaflets appeared reduced in size, chlorotic, with narrow pointed tips. The primary branches collapsed later, and secondary branches were stunted with reduced number of leaves. The flowering was disturbed, less flowers matured, as a consequence pods and seeds were reduced, malformed and low in productivity, which lowered biomass and economic yield and is accompanied by decrease in Cu concentration in leaves and seeds. The quality of seeds deteriorated at deficient Cu as the concentration of proteins, carbohydrates (sugars and starch), protein nitrogen were lowered, and phenols, non-protein nitrogen, increased. Whereas in leaves, the concentration of carbohydrates (sugars and starch), phenols, and non-protein nitrogen were elevated and protein nitrogen was reduced. Copper deficiency also alleviated the concentration of chlorophyll (a and b) in leaves. At deficient Cu, the activity of antioxidative enzyme viz. peroxidase along with that of acid phosphatase and ribonuclease increased in leaves, seeds and pod wall of chickpea.

Physiological and biochemical responses of french bean to excess cobalt

ABSTRACT French bean (Phaseolus vulgaris L.) cv. ‘Anupama’ was grown in refined sand at variable levels of cobalt (Co), i.e., 0.0001 (control), 0.05, 0.10, 0.20, 0.40, and 0.50 mM, supplied as cobalt sulfate. The symptoms of excess Co (0.50 mM) appeared at day 35. In addition to growth depression, the young leaves developed chlorosis from the apex leading toward the base; the chlorosis intensified, changed to necrosis, and the infected leaves dried and withered. Under excess Co (> 0.0001 mM), the flowers produced were fewer in number, smaller, and many failed to mature, leading to lower seed yield. Excess Co (> 0.0001 mM) decreased the biomass, seed yield (number and weight), concentration of chlorophyll, Hill reaction activity, and activity of catalase, and deteriorated the quality of produce (sugars, starch, and protein nitrogen (N)), but it increased the concentration of phenols and activity of certain enzymes, i.e., peroxidase, ribonuclease, and acid phosphatase. The concentration of Co in various parts of French bean increased with an increase in Co supply and that of iron (Fe) decreased concomitantly. The values of threshold of toxicity and toxicity of Co were 26 and 72 μg g−1 in young leaves of French bean, respectively.

Excess Copper‐Induced Oxidative Damages and Changes in Radish Physiology

Abstract To identify the detrimental effects of excess copper in radish (Raphanus sativus) cv. Jaunpuri, plants were grown in refined sand at control (0.001) and 0.1 and 0.2 mM (excess) copper (Cu) supplied as Cu sulphate. Previously plants were maintained for 24 days in complete nutrient solution and on the 25th day, excess Cu was superimposed. After 6 days of metal supply, the visible effects of excess Cu appeared as retardation in growth and interveinal chlorosis of young leaves; chlorosis intensified later with the development of irregular brown spots on lamina. Excess Cu not only reduced the size of leaves but also affected adversely the root development. In radish, Cu toxicity decreased the fresh weight, biomass, root weight, concentrations of total and active iron, chlorophyll, activities of antioxidative enzymes catalase (CAT), and peroxidase (POX), starch phosphorylase (ST) and acid phosphatase (AP) with concomitant increase in Cu accumulation in different parts. These effects were more pronounced at 0.2 than 0.1 mM Cu.

Assessment of disturbances in growth and physiology of carrot caused by chromium stress.

ABSTRACT To see the deleterious effects of excess chromium (Cr) on carrot (Daucus carota L.) the cv. ‘Pusa Keshari’ was grown in refined sand under controlled glasshouse conditions with a complete nutrient solution (without Cr) for 48 days. On the 49th day, pots with two plants each were separated into three sets. One set served as a control. In each of the other two sets, Cr was supplied as dichromate at 0.1 and 0.5 mM to the basal nutrient solution. At 0.5 mM Cr toxicity symptoms appeared at d 52 (4 days after Cr supply) as reduction in growth and leaf size and loss of turgor. Old leaves became chlorotic and wilted. Chlorosis intensified and turned necrotic in another few days. These symptoms spread to next upper leaf. The development of chlorosis in leaves was delayed in plants receiving 0.1 mM Cr. At excess Cr (0.5 mM) in carrot, the biomass, concentration of chlorophylls a and b, iron (Fe), sulfur (S), and phosphorus (P) in shoots, and activity of catalase (CAT) in leaves decreased whereas the concentration of Cr and the activity of peroxidase (POX), superoxide dismutase (SOD), ribonuclease (RNAse), and acid phosphatase (A P) in leaves increased.

Phosphorus Stress Alters Boron Metabolism of Mustard

The study has been made to understand the role of phosphorus in changing the boron (B) metabolism of mustard (Brassica campestris L.) cv. T9 by growing the plants in refined sand at deficient (0.3 μM), adequate (30 μM) and excess (300 μM) levels of boron, each at three levels of phosphorus (P), low (0.15 mM), normal (1.5 mM) and excess (3.0 mM). The synergy between B and P was reflected when low phosphorus accentuated the effects of B deficiency by lowering further the reduced dry weight, total seed yield and increased further the concentration of reducing sugars, phosphorylated protein and activities of acid phosphatase and ribonuclease in B deficient leaves. The effects of excess boron in mustard, viz., reduction in dry weight, seed weight, contents of reducing sugars, organic P, oil content, activity of ribonuclease and stimulating leaf boron, content of inorganic P, phosphorylated protein were accelerated further by combined toxicity of both nutrients. No seeds were produced at deficient B even on increasing the P supply to twice that of adequate amount. The synergy was again observed between B and P when low phosphorus accentuated boron excess effects, i.e., the depression in dry weight, seed yield, reducing sugars, organic P, and oil content and increasing further B and activity of ATPase in young leaves in low P–excess B treatment in mustard.

Chromium Phytotoxicity Alters Metabolism in Radish

ABSTRACT Industrialization has posed an increasing threat to the environment. Effluents from different industries ultimately find their way into water used to irrigate crops. There is a risk that heavy metals accumulating in these agricultural soils may eventually contaminate the human food chain. Radish, an important vegetable consumed by humans, was selected as the test plant. The cv. Jaunpuri was grown in refined sand supplemented daily for 50 days with complete nutrient solution. On the 51st day pots with plants were separated into three lots, one lot served as the control and received only the nutrient solution, and in each of two other lots chromium (Cr) as dichromate was added at 0.1 and 0.5 mM to the basal nutrient solution. At 0.5 mM Cr, toxicity symptoms were observed 5–8 days after treatment expressed as reductions in leaf size accompanied by loss of turgor, and old leaves became chlorotic and wilted. Treatment with Cr reduced growth, biomass, concentration of chlorophyll (a and b), relative water content in leaves, iron, phosphorus, sulphur in shoots (leaves and stem plate) and activity of catalase in leaves, but increased the concentration of chromium, iron, phosphorus, and sulphur in roots, and increased the activity of peroxidase and acid phosphatase in leaves of radish.

Biochemical Changes, Yield, and Quality of Gram Under Boron Stress

Abstract Gram (Cicer arietinum L.) cv. Avrodhi was grown in refined sand at levels of boron (B) ranging from deficiency to excess (0.0033–6.6 mg B L−1). At low (<0.33 mg B L−1) B, apart from marked depression in growth at day 28, deficiency symptoms were initiated as chlorosis of young leaflets. With increase in age, these chlorotic leaflets turned necrotic and shed premature. Biomass weight of pods and seeds was maximum at 0.33 mg B L−1. At 6.6 mg B L−1, toxicity symptoms appeared as marginal necrosis of old leaflets along with growth depression. Later, the necrotic leaflets became completely dry and shed. In low B, activity of acid phosphatase, starch phosphorylase, and ribonuclease increased and that of polyphenol oxidase decreased in leaves of gram. Excess B at 6.6 mg B L−1 increased the activity of starch phosphorylase and acid phosphatase and decreased that of ribonuclease and polyphenol oxidase. Deficiency (<0.33 mg L−1) as well as excess (>0.33 mg L−1) of B deteriorated the quality of gram seeds by lowering seed yield, starch and protein concentration, and increasing the accumulation of phenols and sugars. The concentration of B increased in leaves and seeds with an increase in B supply. The values of deficiency, threshold of deficiency, threshold of toxicity and toxicity are, respectively, 13.5, 32, 190, and 310 µg B g−1 in leaves of gram.

Involvement of excess cadmium on oxidative stress and other physiological parameters of eggplant.

ABSTRACT To examine tolerance of cadmium (Cd) by eggplant (Solanum melongena L.) cv. ‘Hybrid PK 123’, plants were grown in refined sand in complete nutrient solution for 52 days in a glasshouse at ambient temperature. Cadmium sulfate was superimposed on day 53, at variable levels: nil, 0.05, 0.1, 0.2, 0.4, and 0.5 mM. Influence of excess Cd was discernible after 5 days of metal supply at 0.4 and 0.5 mM Cd as depression in growth. At these levels, foliar symptoms were initiated as paling of young leaves at the base progressing upward. With increase in age, affected leaves turned golden yellow and these effects spread to lower leaves. Leaf size and floral initiation were very much restricted. These types of phenotypes induced leaf senescence. Excess Cd reduced the biomass and fruit yield of plants. At higher levels (>0.1 mM) of Cd, fruit formation was completely inhibited and fruits formed at 0.05 and 0.1 mM Cd were smaller in size. Besides this, excess Cd disturbed the metabolism of eggplant by reducing the concentration of chlorophyll (a and b), protein, Hill reaction activity, and activity of antioxidant enzymes—catalase and ascorbate peroxidase; whereas the activity of peroxidase and ribonuclease increased in leaves of eggplant. Cadmium excess reduced the concentration of Fe and Zn and Cd increased that of proline, lipid peroxidation, phenols, reducing sugars and Cd concentration in leaves of eggplant.