Effect of ozone and sulphur dioxide pollutants separately and in mixture on chlorophyll and carotenoid pigments ofOryza sativa

Exposure of rice plants to low concentrations of O₃ and SO₂ singly and in combination showed foliar injury of different levels. The maximum leaf injury was noted in case of O₃+SO₂ treated plants and the minimum in O₃ treated ones. Also the reductions in chlorophylla,b and total chlorophyll and carotenoid contents in leaves exposed to O₃+SO₂ mixtures were higher than the reduction noted in case of each individual pollutant. Thus the results suggest a synergism existing between O₃ and SO₂ regarding plant injury, especially with respect to chlorophyll and carotenoid contents of rice (Oryza sativa).     

Experimental studies on sulfur dioxide injuries in higher plants

Photosynthesis is reversibly inhibited by exposing plants to SO₂. The formation of α-hydroxy sulfonate in the exposed plants is suggested as one of the effects, because this compound inhibits glycolic oxidase which is necessary in the glycolic acid pathway. The suppression of the glycolic acid path should affect various aspects of metabolism in plants, particularly the reduction of the biosynthesis of glycine and serine. In this paper, the biosynthesis of these amino acids in plants exposed to SO₂ was investigated to estimate the significance of the formation of α-hydroxy sulfonate in the plants. The results show that photosynthetic formation of serine was reduced in the exposed plants, and that α-hydroxy sulfonate was formed.     

S02-induced enzymatic changes and ascorbic acid oxidation in Oryza sativa

Field grown rice (Oryza sativa L.) plants exposed separately to 0.25 or 0.5 ppm SO₂ for 1.5 hr daily for 40 days, showed significant decrease of catalase (p < 0.001) and increase of peroxidase (p < 0.001) activities as well as decreases of protein (p < 0.001) and ascorbic acid (p < 0.001) contents associated with leaf lesions, which were proportional to SO₂-dose. Catalase and peroxidase activity levels showed an inverse relationship. It is hypothesized from the molecular structure of both enzymes and from the in vitro relationship between catalase and peroxidase activity that the tetrameric molecules of catalase in vivo might disintegrate into monomeric units with peroxidase activity, which in turn oxidise ascorbic acid and may reduce tolerance of plants to SO₂.     

Effects of SO2 exposure on carbohydrate contents,phytomass and caloric values of wheat plants

This paper reports the results of wheat plants exposed to SO₂. The SO₂-treated and control plant samples were periodically analyzed with respect to their carbohydrate content, caloric values, phytomass accumulations and net primary productivity. An initial increase, but later decrease in all these parameters was recorded in SO₂-treated plants. These effects in wheat plants have been interpreted in terms of energy budget of plants under SO₂-stress condition.     

Responses to sequential exposure to SO2 and salinity in soybean (Glycine max L.)

Soybean plants (Glycine max L. cv. Buchanan) were subjected to one of three levels of salinity preteatment (with electrical conductivities of 0.7, 4.4 and 6.5 dS m^?1) and then exposed to one of three concentrations of SO₂ (1, 145 and 300 bl l ^?1 for 5 h d^?1), or vice versa. Each stress episode lasted 3 weeks. Both salinity and SO₂ deecreased leaf area, root and shoot dry weight and the fresh weight of root nodules. SO₂ induced an increase in the shoot: root ratio and leaf chlorophyll concentrations. Low salinity pretreatment protected plant growth from SO₂ injury, probably by decreasing SO₂ uptake by increasing stomatal resistance. However, high salinity-treated plants, despite also showing stomatal closure, were severely injured by subsequent SO₂ exposure. Prior exposure to SO₂ caused plants to become more vulnerable to salt injury. Plants pretreated with high SO₂ were killed after 12 days of high salt stress. These data suggest that the compensatory mechanisms and predisposition characteristics of salinity and SO₂ largely depend upon the stress levels used.     

Exposure to SO2 and water stress in Picea Abies (L.) Karsten

The purpose of this research was to analyze the responses of Norway spruce Picea abies (L.) Karsten to SO₂, at a subnecrotic concentration (230 μg SO₂ m^?3 ), and to water stress using seedlings and 5 yr-old plants. In a first period, the plants were exposed to SO₂ for 6 weeks; then they were simultaneously exposed to SO₂ and to water stress for 1 week for the case of seedlings and 2 weeks for the 5 yr-old plants. The plants were then rewatered, but maintained under exposure to SO₂. Their morphological and physiological characteristics were analyzed and compared to non-SO₂ exposed plants. It was shown that there were no differences between SO₂ exposed and non-exposed irrigated plants, specifically water content and water potential were not altered. After water stress the non-SO₂ exposed seedlings and plants showed good revival upon rewatering. In contrast, the two simultaneous stresses were very damaging to the plants. Despite a better initial recovery upon rewatering, 50% of the continuously SO₂ exposed plants died and, after 5 weeks of rewatering, the remainder showed altered water content and water potential. These results are discussed.     

Glycolic acid oxidase activity in crop plant leaves

Many workers have revealed the possible role of glycolic acid oxidase in the photosynthesis and the respiration of plant leaves (1, 5) and in the organic acid metabolism of rice plant roots (6). There is also abundant evidence that α-hydroxysulfonates, the bisulfite addition compounds of aldehydes and ketones, are the specific and competitive inhibitors of the enzyme (7, 8). The pevious works (9, 10) showed that a deficient application of potassium increased the content of amino-N and reducing sugars and concomitantly the respiratory activity in sweet potato roots. Such a derangement in the metabolic status of plant roots would be expected to be intimately connected with any changes in the photosynthesis and the respiration of the leaves. This paper, as a preliminary, describes some results from investigations into the glycolic acid oxidase activity in leaves of rice plant- and barley seedlings, sweet potato plants, and taro plants which were grown in solution culture at varying potassium application : the effects of light and plant age on enzyme activity, the activation of the enzyme by FMN addition, the stability of the enzyme during a prolonged incubation of sap from leaves, and the inhibitory effects of specific inhibitors on the enzyme in vitro and in vivo.     

Experimental studies on SO2 injuries in higher plants III: Inhibitory effect of suite ion on 14 CO 2 fixation

Photosynthesis decreases reversibly in plants exposed to SO₂. Photosynthesis recovers when the exposure to SO₂ is discontinued. Inactivation of a photosynthetic enzyme, ribulose-1,5-diphosphate carboxylase, by sulfonation of its SH groups was investigated as a cause of the reversible reduction of photosynthesis. The relationship between the sulfite ion concentration in the reaction mixture and ¹⁴CO₂ fixation catalized by the enzyme which was prepared from alfalfa leaves was explored by using radioactive NaHCO₃. About 50% and 85% inhibitions of ¹⁴CO₂ fixation were observed at 3 × 10^?3 M and 3 × 10^?2 M concentration of sulfite ion in the reaction mixture, respectively. The accumulation of 3 × 10^?4 M sulfite ion on the reaction site of the enzyme involved in the plants which were exposed to SO₂ could considerably reduce the CO₂ assimilation of the plant.     

Reduction in soybean yield after exposure to ozone and sulfur dioxide using a linear gradient exposure technique

A linear gradient field exposure system was modified from one originally described by Shinn et al. (1977) and used to expose field grown soybeans (Glycine max cv Hark) to a concentration gradient of a mixture of two gaseous pollutants: SO₂ and 0₃. Since this technique does not use enclosures, study plants experienced near ambient fluctuations in environmental conditions, including wind, and hence were exposed to widely fluctuating pollutant concentrations. Plants in the gradient system were exposed to both pollutants for 57 h on 12 days during the pod-filling period (31 August–17 September). Mean concentrations during the 57 h of exposure at the ‘high’ end of the gradient were 0.16 and 0.06 µl l^?1 (PPM) SO₂ and O₃, respectively, with 10 h at greater than 0.25 and 0.10 µl^?1 SO₂ and O₃, respectively. Total doses for these plants were estimated to be 9.0 and 3.5 µl^?1 · h SO₂ and O₃, respectively. Comparison with plants exposed to ambient air indicated that exposure to SO₂ and O₃ reduced total yield per plant and dry mass per bean by as much as 36 and 15 %, respectively. Since concurrent exposure to a much higher dosage of SO₂ alone (20.2 µl l^?1 · h) was observed in a separate experiment to have no significant effect on yield, 03, although present at moderately low levels, was probably responsible (alone or synergistically with SO₂) for the greatest reduction in seed size and yield.     

Growth responses of maize,soybean, and tomato to sulphur dioxide and ozone exposure patterns utilizing an incomplete block factorial experimental design

Maize (Zea mays L.), soybean (Glycine max L.), and tomato (Lycopersicon esculentum Mill.) plants were grown in a controlled environment and exposed for 6 hr daily for 7 days to O₃ at 0.15 μL L^?1 and/or SO₂ at 0.30 μL L^?1 (daily exposures). Some plants exposed daily to O₃ were also exposed to SO₂ for 6 hr on the first, third, fifth, or seventh day of O₃ exposure (variable exposures) and some plants exposed daily to SO₂ were treated similarly with O₃ to determine the growth effects of O₃ or S0₂ pre- and/or post-treatments on S0₂ and O₃ mixture response. Growth sensitivity to 6 hr S0₂ or 6 hr O₃ treatments was generally affected by the previous history of O₃ or SO₂ exposure, respectively. Species differed in the number of days of O₃ or SO₂ treatments required to elicit maximum sensitivity to a single 6 hr O₃ and SO₂ treatment. Linear contrasts compared variable with daily exposures for the S0₂ and O₃ regimes. Plants exposed to the gas mixture for a single day (variable exposures) tended to be smaller than those exposed to the gas mixture daily, with the exception of soybean exposed to SO₂ during daily O₃. The six treatments were carried out in eight exposure chambers, as a partially balanced incomplete block design in blocks of four due to separate environmental control of the exposure facilities. The partially balanced incomplete block design proved to be about 2.6 times as efficient as a complete block design. The inclusion of covariates further increased precision.     

Estimation of critical limit for zinc in rice soils

Abstract

Twenty surface soil samples were collected from Nainital Tarai (foothills of Himalya) where “Khaira”; disease (Zn deficiency of rice) is prevalent. Rice (Oryza sativa L. variety IR‐8) was grown in pots for 8 weeks after transplanting. Experiments were conducted to determine the suitability of five soil Zn extractants: dilute acid (HCl + H₂SO₄) mixture; DTPA‐(NH₄) ₂CO₃, pH 7.3; dithizone; NH₄OAc, pH 4.6; and 2N MgCl₂ to predict Zn deficiency. Critical values for soil available Zn were established for rice by the old and new Cate and Nelson procedures¹.

Zinc extracted from the soils with dithizone; NH₄OAc, pH 4.6; 0.2N MgCl₂. and DTPA‐(NH₄) ₂CO₃ pH 7.3 was significantly correlated with the uptake of Zn by the rice plants. The correlation between Zn extracted with the dilute acid (HCl + H₂SO₄) mixture and plant Zn was not statistically significant. The ex‐tractants which extracted greater quantities of Zn gave higher critical values and vice versa. It is concluded that all extracting solutions except the dilute acid (HCl + H₂SO₄) mixture were found to he suitable for predicting available Zn in rice soils of Tarai.     

Response of eight tropical plants to enhanced ammonia deposition under field conditions prevalent with SO2 and NH3

The impact of SO₂ on the deposition of ammonia and the response of eight tropical tree species to excess deposition of ammonia was investigated. This was achieved by studying physiological aspects like total sugars, protein, nitrate reductace (NR) activity, organic/inorganic nitrogen ratio, specific leaf area and foliar injury in plants growing under field conditions prevalent with SO₂ and NH₃. Analysis of water soluble substances present on foliar surfaces of the trees indicated enhanced NH₄ ⁺ deposition and thereby result in enhanced foliar protein contents. Though the enhanced nitrogen was almost the same in different plants, the plants exhibited differential metabolic disturbances. Critical analysis of the results indicated three distinct types of plant response. Plants like Azadirachta indica, Acacia auriculiformis and Bambusa arundinaceae maintained enhanced total sugars and NR activity and incorporated excess NH₄ ⁺ into proteins, thus enabling the plant to compensate/alleviate SO₂ induced injury. Ficus benghalensis and Ficus religiosa maintained unaltered total sugars and NR activity and could partly incorporate NH₄ ⁺ into proteins, thus modifying the SO₂ impact to some extent. Dalbergia sissoo, Eucalyptus rostrata and Mangifera indica could not incorporate the excess NH₄ ⁺, mainly due to declined total sugars. The results indicate the ability of a plant to undergo species specific metabolic changes in order to cope with the excess nitrogen deposition, which may ultimately result in increasing or decreasing tolerance to SO₂.     

The relationship of soil and leaf nutrients to rice leaf oranging

A symptom called leaf‐oranging, indicating a deficiency of many nutrients, occurs in paddy rice (Oryzasativa L.) when production expands into some upland soils. Rice (Gui Chou cv.) was grown in culture pots in a flooded, weathered, upland soil (Nacogdoches) and compared to rice growth in a flooded soil currently used for paddy rice production (Dacosta) in Texas to understand the soil and plant factors involved in leaf‐oranging. Fertilizer rates of 0, 10, and 100 mg N/kg as (NH₄)₂SO₄ were applied to each soil along with phosphorus (P) and potassium (K) fertilizer. The orange Leaf Index (OLI), a measure of leaf‐oranging, was determined weekly and increased to 60–70% for plants grown in the upland soil but its progression was delayed by higher N treatments. No leaf‐oranging was observed in the paddy soil. The soil evoking leaf‐oranging was low in silicon (Si) and high in iron (Fe). In addition, analysis of leaves from these plants showed 19–25% higher leaf ammonium‐nitrogen (NH₄‐N), 9–137% higher manganese (Mn) levels and lower total N:NH₄ concentration compared to normal rice leaves four weeks after transplanting. This inferred that leaf‐oranging probably was associated with some degree of NH₄‐N toxicity and antagonism with K. Leaf‐oranging was also associated with low calcium (Ca) assimilation or Ca uptake inhibition because of the heavy Fe‐oxide coating of the roots of the affected rice plants. In this experiment, leaf‐oranging was not associated with toxic levels of Fe or Mn.     

Sulfur dioxide resistance of Indian trees

Saplings of Tamarindus indica, Mangifera indica, Pithecolobium dulce, Ficus rumphii, Ficus bengalensis, Holoptelea integrifolia, Syzygium cumind, and Psidium guajava were exposed to varying concentrations of SO₂ and chlorophyll, protein, amino acids, starch, total soluble sugars and reducing sugars were determined. In general, it was observed that on exposure to SO₂ in susceptible plants most of the biochemical constituents accumulated in higher amounts while in plants showing visible damage at extremely high exposure concentration a reverse pattern was obtained.     

Sulfur dioxide resistance of Indian trees I. Experimental evaluation of visible symptoms and SO 2 sorption

Saplings of 12 species of common Indian trees were exposed to varying concentration of SO₂ to determine the level of SO₂ causing no injury, mild injury and severe injury in plants. The following order of sensitivity was emerged, T. indica > P. dulce > M. indica > F. rumphii > H. integrifolia > B. ceiba > F. bengalensis > A. indica > F. religiosa > S. cuminii > P. guajava > F. racemosa. SO₂ sorption was extremely low in T. indica and M. indica while F. religiosa and F. racemosa exhibited best efficiency of SO₂ Aorption. A correlation was found between the efficiency of SO₂ sorption and alkalinity of cytoplasmic pH. Similarly plants rich in sulfite oxidase, in general, exhibited a better resistance. No single intrinsic factor could be held responsible for the manifested response of a tree towards SO₂.     

Effects of inorganic fertilizers and micronutrients on methane production from wetland rice (Oryza sativa L.)

We compared the effects of adding different forms of nitrogenous fertilizers on the production of CH₄ in soil and on CH₄ emission from rice plants, Urea and diammonium phosphate gave the highest rates of CH₄ production from the soil and emission through rice plants, followed by (NH₄)₂SO₄. NaNO₃ was the least effective. The effects of micronutrients like Mo, Ni, or B were more prominent than those of Fe, Mn, Zn, V, or Co. It is concluded that CH₄ emission from rice paddies is influenced by both macro- and micronutrients, through effects on both microbial methanogenesis in soil and elimination through rice plants as a consequence of the effects on plant growth.     

Does SO2 fumigation change the chemical defense of woody plants: The effect of short-term SO2 fumigation on the metabolism of deciduous Salix myrsinifolia plants

The effect of a moderate increase in atmospheric sulphur dioxide on the production of phenolic secondary chemicals, soluble sugars and phytomass distribution within plants was investigated in six willow (Salix myrsinifolia Salisb.) clones. The plants were cultivated for 3 weeks under 0.11 ppm of SO₂ (300 μg m^?3). The production of salicin and chlorogenic acid was significantly reduced under increased SO₂. However, salicortin, 2′-O-acetylsalicortin, (+)-catechin and two unknown phenolics did not show any clear trend. The increase in SO₂ did not affect the glucose, fructose and sucrose contents. The final weight of the SO₂-treatment plants was significantly greater than that of the control plants: the leaf, stem and root phytomass was from 14 to 48% greater under increased SO₂. All the clones showed the same trend, although there was a significant variation in phytomass production. Our results indicate, although not consistently that even a short-term exposure of enhanced atmospheric SO₂ may change moderately the accumulation pattern of willow phenolics.     

Casuarina and Eucalyptus response to single and multiple gaseous air pollutants

Casuarina cunninghamiana and Eucalyptus camadulensis (Egyptian var.) plants were exposed to 0.20 and 0.40 μL L^?1 O₃, SO₂ or NO₂ for 6 hr daily for 10 days. Eucalyptus plants were very sensitive to SO₂ and NO₂ and less sensitive to O₃. Casuarina plants were insensitive to the 3 gases. The rate of sorption of the 3 gases was estimated over a 10 day exposure to 0.20 μL L^?1 pollutant concentration singly and in a 3-gas mixture. Casuarina plants removed air pollutants more efficiently than Eucalyptus plants. Leaves of both species generally sorbed about the same volume of a given gas from the mixture and from the same single gas. The sorption rate over the 10 day exposure was almost constant after a higher sorption rate during the first day for both species.     

Chlorophyll reduction in western wheatgrass (Agropyron smithii Rydb.) exposed to sulfur dioxide

Chlorophyll concentrations in western wheatgrass, an important dominant species in the grasslands of the northern Great Plains of North America, exposed to controlled SO₂ concentrations were examined. Concentrations of chlorophylls a and b were significantly decreased, without visible plant necrosis. Chlorophyll-a was more sensitive than chlorophyll-b. Sensitivity of chlorophylls to SO₂ changed as the growing season progressed, indicating cumulative effects and interactions with normal senescence.     

CHLOROSIS IN WILD PLANTS: IS IT A SIGN OF IRON DEFICIENCY?

ABSTRACT

Chlorosis in crops grown on calcareous soil is mainly due to iron (Fe) deficiency and can be alleviated by leaf application of soluble Fe²⁺ or diluted acids. Whether chlorosis in indigenous plants forced to grow on a calcareous soil is also caused by Fe deficiency has, however, not been demonstrated. Veronica officinalis, a widespread calcifuge plant in Central and Northern Europe, was cultivated in two experiments on acid and calcareous soils. As phosphorus (P) deficiency is one of the major causes of the inability of many calcifuges to grow on calcareous soil we added phosphate to half of the soils. Leaves in pots with the unfertilized and the P-fertilized soil, respectively, were either sprayed with FeSO₄ solution or left unsprayed. Total Fe, P, and manganese (Mn) in leaves and roots and N remaining in the soil after the experiment were determined. In a second experiment, no P was added. Leaves were either sprayed with FeSO₄ or with H₂SO₄ of the same pH as the FeSO₄ solution. Degree of chlorosis and Fe content in leaves were determined. Calcareous soil grown plants suffered from chlorosis, which was even more pronounced in the soils supplied with P. Newly produced leaves were green with Fe spray but leaves that were chlorotic before the onset of spraying did not totally recover. H₂SO₄ spray even increased chlorosis. This demonstrated that chlorosis was due to Fe deficiency. As total leaf Fe was similar on acid and calcareous soil, it was a physiological Fe deficiency, caused by leaf tissue immobilization in a form that was not metabolically “active”. Iron in the leaves was also extracted by 1,10-phenanthroline, an Fe chelator. In both experiments, significant differences between leaves from acid and calcareous soil were found in 1,10-phenanthroline extractable Fe but not in total leaf Fe, when calculated on a dry weight basis. Differences in 1,10-phenanthroline extractable Fe were more pronounced when calculated per unit dry weight than calculated per leaf area, whereas the opposite condition was valid for total leaf Fe.