Sasadhar Jana

Glycolate metabolism of three submersed aquatic angiosperms during ageing

Abstract The glycolate metabolism of three submersed aquatic macrophytes, Potamogeton pectinatus L., Vallisneria spiralis L. and Hydrilla verticillata (L.f.) Royle, was studied by estimating the endogenous levels of glycolate and hydrogen peroxide (HP2O2) and assaying the activities of glycolate oxidase and catalase. The highest rate glycolate oxidase activity was recorded at pH 8.0, 7.6 and 7.4 for Potamogeton, Vallisneria and Hydrilla, respectively, while pH levels above and below this value markedly reduced the glycolate oxidase activity. The optimum glycolate oxidase activity of the three species was obtained when the reaction time was restricted to 10 min. Both the glycolate content and the activity of glycolate oxidase in the three leaf age groups (young, mature and old) were highest in mature leaves of these aquatic species. The glycolate content in mature leaves was highest in Hydrilla which also showed the lowest glycolate oxidase activity. Lowest glycolate content and highest glycolate oxidase activity were recorded in Potamogeton. An intermediate picture was observed in Vallisneria. The H2O2 content gradually increased with leaf age, while the catalase activity decreased. The content of H2O2 in mature leaves was highest in Vallisneria and lowest in Hydrilla. The catalase activity was also lowest in the former of the three species. During ageing of isolated mature leaves in the dark, there was a gradual decline in glycolate metabolism with increase in leaf age in Vallisneria and Hydrilla, but not in Potamogeton which showed a rise in glycolate oxidase activity after 3 days of induced ageing. Kinetin promotd glycolate metabolism in mature leaves of the three submersed plants during induced ageing, while ethrel and abscisic acid (ABA) showed an opposite effect.

Synergistic effects of heavy metal pollutants on senescence in submerged aquatic plants

The effects of many combinations of toxic concentrations of heavy metal pollutants, viz., mercuric chloride, lead acetate, cadmium chloride and cupric sulphate, on the senescence of isolated mature leaves of submerged aquatic plants, Potamogeton pectinatus L., Vallisneria spiralis L., and Hydrilla Verticillata (L.f) Royle were studied. All of the combinations of heavy metal pollutants caused senescence in all three species by decreasing chlorophyll, DNA, RNA, protein and dry wt, and increasing free amino acid, tissue permeability, the activities of protease and RNase, and the ratio of acid to alkaline pyrophosphatase activity over control values. The effects were highest in Potamogeton and lowest in Hydrilla. The degree of senescence in the three submerged plants by combinations of toxic concentrations of heavy metal pollutants is much higher due to synergism than that by individual heavy metal pollutants.

Heavy metal pollutant tolerance of Azolla Pinnata

The effects of Hg, As, Pb, Cu, Cd, and Cr (1, 2, and 5 mg L−1 each) on Azolla pinnata R. Br. were analyzed. The treatments (2 and 5 mg L−1) of the heavy metal pollutants decreased Hill activity, chlorophyll, protein and dry wt, and increased tissue permeability over control values. The effects were most pronounced with the treatment of 5 mg L−1. The harmful effects of the metals were, in general, found by the treatments in the order: Cd 〉 Hg 〉 Cu 〉 As 〉 Pb 〉 Cr. There was no significant change in these parameters at 1 mg L−1 of the metals over control. Thus Azolla pinnata shows tolerance to the heavy metals tested up to 1 mg L−1 each.

Glycolate metabolism of three submersed aquatic angiosperms: Effect of heavy metals

Abstract Glycolate metabolism and the effect of heavy metals e.g. mercury, lead, cadmium and copper, on glycolate metabolism of the three submersed aquatic macrophytes, i.e. Potamogeton pectinatus L., Vallisneria spiralis L. and Hydrilla verticillata (L.f.) Royle, were studied by estimating the endogenous levels of glycolate and hydrogen peroxide and assaying the activities of glycolate oxidase and catalase. The glycolate content was highest in Hydrilla , which also showed the lowest glycolate oxidase activity. Lowest glycolate content and highest glycolate oxidase activity was recorded in Potamogeton , while an intermediate state was observed in Vallisneria . The initial content of hydrogen peroxide was highest in Vallisneria and lowest in Hydrilla . The catalase activity was lowest in Vallisneria spiralis . Compared with the initial activity, the activity of the enzyme glycolate oxidase declined in Vallisneria and Hydrilla but rose in Potamogeton after three days of ageing of isolated leaves. Hydrogen peroxide content increased and catalase activity decreased in all three species during ageing. The highest content of hydrogen peroxide in Potamogeton was associated with maximum decline in catalase activity. The four heavy metals produced different effects on glycolate metabolism in the three species of aquatic macrophytes tested. All the heavy metals decreased glycolate content in Potamogeton , but in Vallisneria Hg and Cu caused it to increase while Pb and Cd gave a decrease. In Hydrilla , glycolate content decreased with Hg and Pb but increased with Cd and Cu. Glycolate oxidase activity was increased by Hg, Cd and Cu in Potamogeton , but decreased with Pb, whereas in Vallisneria this activity was decreased by Hg and Pb but increased by Cd and Cu. The activity of this enzyme was decreased by Hg, Cd and Cu but increased by Pb in Hydrilla . In Potamogeton and Vallisneria all the heavy metals except Pb increased H 2 O 2 content, while in Hydrilla the effect was reversed. Catalase activity was decreased by all the heavy metals in Potamogeton and Vallisneria but increased in Hydrilla . A metal stimulatory to glycolate metabolism when treated alone became inhibitory in the presence of another, and the inhibitory metals became stimulatory to this metabolism in combination treatments. It was concluded from these results that the glycolate metabolism was stimulated in Potamogeton and inhibited in Hydrilla by most of the heavy metals used. Vallisneria was intermediately affected by these metals.

Photosynthetic, photorespiratory and respiratory behaviour of three submersed aquatic angiosperms.

Abstract The rates of dark respiration, net and apparent photosynthesis and photorespiration in three submersed aquatic macrophytes, viz., Hydrilla verticillata (L.f.) Royle, Vallisneria spiralis L. and Potamogeton pectinatus L., were studied by estimating dissolved and gaseous O2. Among the three species, Hydrilla showed minimum dark and photorespiration and maximum apparent photosynthesis, while Potamogeton showed almost the reverse. The vigorous growth and dominance of Hydrilla and slender growth of Potamogeton in local ponds and lakes of this locality might be ascribed to these differences in physiological behaviour. Vallisneria was intermediate in this respect. Based on the above physiological characteristics, it was inferred that all the above three species are basically C3 plants. There was a gradual decline in physiological processes with increase in leag age in the case of Vallisneria. This age effect was also substantiated from data obtained from induced-ageing experiments. It was concluded that ageing has a similar effect on aquatic submersed macrophytes as in terrestrial plants.

Effects of plant growth regulators on Hill activity of submerged aquatic plants during induced senescence

Abstract Effects of plant growth regulators on Hill activity during induced senescence of leaves of three submerged aquatic plants Vallisneria spiralis L., Hydrilla verticillata (L.f.) Royle and Potamogeton pectinatus L., and a terrestrial plant Spinacia oleracea L. were studied. Hill activity was reduced by 39.3, 42.7, 45.2 and 245.1 μmol DCIP (2,6-dichloroindophenol) (mg chl) −1 h −1 in Vallisneria, Hydrilla, Potamogeton and Spinacia , respectively. During induced senescence of isolated mature leaves, Hill activity declined with increasing incubation time in all species. Kinetin (0.23 mM) treatment reduced the loss of Hill activity; while both 0.69 mM ehthrel and 0.075 mM ABA treatments decreased it in each species. The effect of kinetin was greatest in Spinacia , followed by Potamogeton, Hydrilla and Vallisneria , while the effect of either ethrel or ABA or both was greatest in Potamogeton , followed by Spinacia, Vallisneria and Hydrilla . Kinetin pre-treatment for an optimal period (12 h) followed by treatment with either ethrel or ABA partially removed the inhibitory effect of the latter on Hill activity. Pre-treatment of tissues with either ethrel or ABA solution, restricted to 12 h, followed by kinetin treatment markedly reduced the promotive effect of kinetin on the Hill activity of these species.

Ethylene production and senescence in submerged aquatic angiosperms

Abstract Ethylene evolution and its relationship with leaf senescence was studied in three submerged aquatic plants, Potamogeton pectinatus L., Vallisneria spiralis L. and Hydrilla verticillata (L.f.) Royle and in a terrestrial plant Spinacia oleracea L. The rate of evolution of ethylene gradually increased with age of intact leaves in all the four species. The highest rate was encountered in Potamogeton followed by Spinacia, Vallisneria and Hydrilla in all the age groups of leaves. During ageing of isolated mature leaves in the dark, there was a gradual increase in the rate, until it declined sharply at the senescent phase of the leaves of three aquatic species, except in Spinacia . Kinetin treatment suppressed ethylene production while ethrel and abscisic acid (ABA) enhanced it. The complex mechanisms of ethylene action in leaf senescence are discussed.

Physiology of some submersed aquatic angiosperms: effects of heavy metals

Summary1.Potamogeton showed the highest rates of dark respiration, net photosynthesis, photorespiration, and Hill activity, and the highest chlorophyll a:b ratio, and the lowest photosynthesis:photorespiration ratio.Hydrilla showed the lowest dark respiration, photorespiration and chlorophyll a:b ratio, and the highest apparent photosynthesis and photosynthesis: photorespiration ratio.Vallisneria was intermediate in this respect.2.Induced aging lowered the Hill activity, the rates of net and apparent photosynthesis, and the photorespiration, and increased the dark respiration and the photosynthesis: photorespiration ratio in all the three species. The chlorophyll a:b ratio increased inHydrilla but decreased in the other two species during aging.3.All the heavy metal compounds lowered the dark respiration, the Hill activity, and the net and apparent photosynthesis in all the three species exceptPotamogeton where Cu increased the dark respiration. All the metals always increased the photosynthesis: photorespiration ratio. The chlorophyll a:b ratio was increased inHydrilla and lowered in the other two species. The effects of metals on the photorespiration were variable.4.Treatments of heavy metal compounds in different combinations produced more or less similar effects on the physiological parameters as were obtained when applied alone