Fighting against POLLUTION to Save Environment

Effects of gaseous ammonia on plant growth and production

Ind. J. Air Pollution Control, 2(1); 19-23, 1979.
S. B. Chaphekar and D. B. Boralkar
Department of Botany, The Institute of Science, 15, Madam Cama Road, Bombay-400032

Effects of a 3-hr fumigation to 50 ppm ammonia on Abelmoschus esculentus Moench. var. Pusa Savni, Trigonella foenum-graecum L., Cyamopsis tetragonaloba Taub. var. Pusa Navbahar and Crotalaria juncea L., were studied. It was observed that the percentage and rate of seed germination were affected adversely in all the species and the fumigated plants had reduced root and shoot growth except in Abelmoschus where the effect appeared stimulatory. Visible symptoms of leaf injury were noticed within 24 hours after fumigation in Cyamopsis and Crotalaria. Chlorophyll contents were reduced in all the four species, maximum being in Trigonella and minimum in Abelmoschus. Growth performance studies revealed that a 30-day period after fumigation, was not enough for complete recovery of plants subjected to fumigation, as indicated by the low dry matter production, short shoot length, small number of nodes and small internodes in all ammonia-exposed species.

INTRODUCTION

Ammonia has been implicated as an air pollutant at least since 1893 (Treshaw, 1970), but not in the usual sense. The damaging ammonia generally escaped from refrigerator precooling systems of cold storage rooms. Less frequently, anhydrous ammonia used as a fertilizer or escaped during its manufacture or nitric acid damaged nearby vegetation. It is also found in the atmosphere of metropolitan areas, receiving pollutants from various combustion processes like domestic incineration, automobile engines, etc. Ambient concentrations of ammonia as high as 20 pphm from these sources have been reported (Cholak, 1952). Zutshi (1971) estimated that around 5 tonnes of ammonia is liberated every year in the Bombay environment.

Sorauer summarized the knowledge regarding ammonia phytotoxicity in 1914 (Treshaw, 1970). Symptoms consisted of dark or complete blackening of leaves, bleaching of leaves of barley, white rye; wheat developed rust spots, especially along the leaf margins. Azalea chestnut leaves developed dark brown lesions which turned black the next day. Red azalea flowers developed white wedge-shaped spots. Old spruce seedlings became black while young seedlings turned reddish yellow.

Ramsey (1953) and Brennan et al. (1962) have extensively studied the effects of ammonia on plants. Thronton and Setterstrom (1940) found that ammonia fumigation at 40 ppm for one hour markedly injured tomato, sunflower, buckwheat and coleus plants. Concentration of 8.3 ppm for five hours produced slight injury. Mildest symptoms consisted of marginal chlorosis. The work presented here is an attempt to understand the sensitivity of some common plants to gaseous ammonia.

MATERIALS AND METHODS

Fumigation technique

At NTP, 17 gm of ammonia occupies 22,400 ml. At 27°C and 760 mm pressure, 17 gm occupy 24,640 ml. Accordingly, 11.5 ml of 1M freshly prepared liquor ammonia was necessary for occupying a chamber of 5.44 m³ capacity to produce a concentration of 50 ppm. Five mini fans were used for circulation.

Estimation of gaseous ammonia

Air from the chamber was sucked at 2 L/min and passed through a bubbler containing 0.02N H₂SO₄. After addition of Nessler’s reagent, absorbance was measured at 370 nm. Calculations followed Leveggi et al. (1973).

Seeds of four plant species were soaked and germinated. Fifty seeds per species were exposed to 50 ppm ammonia for 3 hours. Germination was recorded for 5 days. GI values were calculated by Carley & Watson (1968). 15-day-old plants of each species were also fumigated and chlorophyll estimated.

RESULTS AND DISCUSSION

Seed germination decreased by 17% in Abelmoschus, 65% in Crotalaria, 61% in Cyamopsis and 74% in Trigonella. GI values also reduced considerably. Plants exhibited visible injury and reduced chlorophyll content. After 30 days, fumigated plants showed reduced shoot length, nodes, internodes and biomass.

Table 1 : Effect of a 3-hr fumigation with 50 ppm ammonia on seed germination

C = Control    F = Fumigated    s.d = Standard Deviation