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How the efficiency of photosynthesis depends on wavelength (green).

Cadmium (Cd) is a heavy metal toxic to all organisms (Lagerwerff, ; Chakravarty and Srivastava, ). The accumulation of Cd in biotic systems as a consequence of human activities is becoming a major environmental problem. The application of sewage sludge, city waste, and Cd-containing fertilizers causes the increase of Cd content in soils (Williams and David, ). Cd is easily taken up by plants and then enters the food chain, resulting in a serious health issue for humans. For instance, people will suffer from renal tubular disease if they consume rice with relatively high Cd content (Watanabe et al., ). Therefore, addition of toxic heavy metals into soil and transference of these metals into the food chain have been a matter of concern to people in arable soils (Grant et al., ). The presence of excessive amount of Cd in soil causes many toxic symptoms in plants, such as reduction of growth, especially root growth (Weigel and Jäger, ), disturbances in mineral nutrition and carbohydrate metabolism (Moya et al., ), and may therefore strongly reduce biomass production. The reduction of biomass by Cd toxicity could be the direct consequence of the inhibition of chlorophyll synthesis (Padmaja et al., ) and photosynthesis (Bazzaz et al., ; Baszynski et al., ). Some studies reported a marked reduction in photosynthetic rate for different plant species under exposure to Cd stress (Sawhney et al., ; Sheoran et al., ; ). Vegetables growing in medium with high level of Cd showed deleterious effect in photosynthetic processes, such as chlorophyll content and photosynthesis (Baszynski et al., ; Padmaja et al., ; Satyakala, ), the activities of related enzymes (Ouariti et al., ; ; Ascencio and Cedeno-Maldonado, ; Weigel, ; ) and photochemical reaction (Li and Miles, ; Skorzynska and Baszynski, ). In contrast, Haag-Kerwer et al.() reported that photosynthesis in Brassica juncea was not affected even when it was exposed to 25 μmol/L Cd, while transpiration showed significant decline, in particular, under lower light conditions (≤300 μmol photons/(m2·s)). It is very imperative to determine the effect of Cd toxicity on photosynthesis of tomato as it is one of the most important vegetables in the world.

We wanted to test how something affected plants, but we couldn't*t decide on a factor to test.

The interstitial water of the Long Island Sound, 2 km off shore, contained concentrations ranging from 11.2 to 42 µg ammonia/litre (Gold-haber & Kaplan, 1974).

ENVIRONMENTAL HEALTH CRITERIA FOR AMMONIA

We will then relate the previous result to the effect acid rain has on the environment.

The detoxification of excessive ammonia places a severe strain on the carbohydrate metabolism of the plant which subsequently results in foliar injury, and growth effects, and thus may modify plant community composition.

Except in open oceans, exposure to environmental levels produces many chronic effects (including reduced growth, decreased survival, impaired reproduction) and may increase susceptibility to disease and also cause histopathological changes.

Effects on experimental animals and in vitro test systems

However, we will also study the effects of acid rain by relating our data to a natural environment.

Reproduction, Embryotoxicity, and Teratogenicity Charles & Payne (1966b) studied the effects of graded concentrations of atmospheric ammonia on the performance of laying hens.

Rabbits given 0.1 g ammonium hydroxide/kg body weight (as a 0.5 - 1.0% solution) by gavage, initially, on alternate days and then daily for up to 17 months, had enlarged adrenal glands (Fazekas, 1939).

The addition of ammonium sulfate increased the rain's acidity decreasing plant life.
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Evaluation of the health risks for man and effects on the environment

Treatment of virgin female rabbits with ammonium carbonate, chloride, hydrophosphate, sulfate, or hydroxide at 0.1 - 0.2 g/kg body weight, orally, on alternate days, for periods of 3 weeks separated by 1-week intervals of no treatment, was associated with enlargement of the ovaries, follicle maturation, and formation of corpora lutea (Fazekas, 1949).

EFFECTS ON ORGANISMS IN THE ENVIRONMENT

and 3 females/ or 20% of dietary N consumption (no (1970)diammonium group was replaced by N effect on these citrate as from equimolar parameters at 5% equimolar mixture of designated 81 days 1600 322 (20% either) slight mixture NH4+ salts replacement) decrease in weight gain, BUN and food consumption-------------------------------------------------------------------------------------------------------------------a Estimated for all studies except Gupta et al.

EFFECTS ON EXPERIMENTAL ANIMALS AND IN VITRO TEST SYSTEMS

(1979) 3-4/group containing 6.4% crude and fat of carcass protein unaffected; plasma- and urine-urea- nitrogen increased but blood-ammonia- nitrogen level unaffected; no effect on haematological values; no gross abnormalities or lesionsDiammonium pig, 27.3 kg basal diet contained 81 days 820 161 (10% no effect on weight Wehrbeinphosphate 3 males and 16% protein; 0,5,10, replacement) gain, BUN, or food et al.

EVALUATION OF HUMAN HEALTH RISKS AND EFFECTS ON THE ENVIRONMENT

One hundred and sixty rabbits (96 female, 64 male) received, twice daily, 50 - 80 ml of a 0.5% ammonium hydroxide solution (~135 - 210 mg/kg body weight), in gradually increasing doses.

Effects on Experimental Animals and In Vitro Test Systems1.7.1.

(contd.)-------------------------------------------------------------------------------------------------------------------Ammonium Species, Mode of Duration Daily Intakea Response Referencesalt No/group, administration (mg/kg (mg NH3/kg sex body body weight) weight)b-------------------------------------------------------------------------------------------------------------------Diammonium pig, male 3.75% diammonium 28 days 1820 274 body weight gain Kagota etcitrate 22.5 kg, citrate in diet increased but % meat al.

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