K. J. Ahmad

Do leaf surface characters play a role in plant resistance to auto-exhaust pollution?

Summary The significance of micro-morphologica1 leaf surface characters of plants in indication and mitigation of auto-exhaust pollution has been investigated. For the purpose of the study, the following plant species growing along roadsides in low and high traffic density areas have been selected: Asparagus racemosus , Azadirachta indica , Bougainvillea spectabilis , Cassia fistula , Ficus religiosa , Nerium indicum , Polyalthia longifolia and Thevetia neriifolia . These plants were continuously exposed to automobile emissions. As compared to control plants, the leaf surface structures changed significantly in the exposed plants. The epidermal cells collapsed, cell boundaries were irregularly fused, and a two-fold increase in stomatal frequency and trichome length could be observed. Epicuticular wax also lost its original shape, got disorganised and subsequently eroded, forming patches of a crust on the cuticle. While the surface structural changes were significant, the phenology of these plants remained unaffected by auto-exhaust pollution. The investigated species though manifesting above changes remained normal and healthy and, therefore, they may be recommended for growing along roadsides in areas polluted by automobile emissions.

Impact of fly ash soil amendment on seed germination, seedling growth and metal composition of Vicia faba L.

Abstract Fly ash disposal is a major problem in and around thermal power plants. In order to find out a solution to this problem, a study was conducted to test fly ash suitability for application to agricultural soils in a definite proportion for better plant growth. While lower application of fly ash enhanced seed germination as well as seedling growth, higher application either delayed or inhibited these processes drastically. Fly ash application to the agricultural soils increased Ni plant uptake but reduced that of Cr and Cu.

Effect of cement dust on the growth and yield of Brassica campestris L.

Plants of Brassica campestris L. var. G-S20 were treated with cement dust, at rates of 3 (B(1)), 5 (B(2)) and 7 (B(3)) gm(-2) day(-1) for 90 days. Treated plants showed a consistent reduction in growth, photosynthetic pigments, yield and oil content over control plants. The overall phytomass of treated plants was significantly decreased, the maximum reduction being 64.8% in B(3) plants, followed by B(2) plants (55.3%) and B(1) plants (43.69%) at 60 days. The effect on oil content was also greatest in B(3) plants, where it was decreased by 6.13%.

ATMOSPHERIC LEAD POLLUTION FROM VEHICULAR EMISSIONS – MEASUREMENTS IN PLANTS, SOIL AND MILK SAMPLES

The changing levels of lead (Pb) in the soil and vegetationalong two National Highways near Lucknow, India, wereinvestigated. The pattern of Pb deposition, as reflected bysoil Pb burdens, showed decrease in concentration withincreasing distances from the road margins. At both the sitesPb concentration was above background concentration even atthe soil core depth of 15 cm. Oryza sativa, Colocasiaesculentum, Luffa cylindrica and Cynodon dactylonplants contained a high mean concentration of Pb over theirrespective controls, with more accumulation in the undergroundportions of the plants. Milk samples, collected from cattlethat normally graze on the roadside pasture-lands dominatedby Cynodon dactylon, contained Pb at an elevatedconcentration.

Growth response and element accumulation in Beta vulgaris L. raised in fly-ash-amended soils.

Fly-ash disposal is a major problem in and around coal-fired power plants. Although the fly-ash contains several essential minerals, its application in agricultural practices is uncommon in India as elsewhere. The present study was undertaken to elucidate the possibility of fly-ash application to agricultural soils to improve crop yields. Three different amounts of fly-ash (2, 4 and 8% w/w) were mixed with soil in 1 m2 plots and seeds of Beta vulgaris were sown in these soil-amended plots. Plants and soils were sampled at 20, 40, 60 and finally at 80 days (each had five replicates) and analysed with respect to plant growth and yield and the concentration of the elements both in under- and above-ground parts. The data were subjected to two-way analysis of variance and Duncans multiple range test.The results revealed that fly-ash application, particularly in higher amounts (4 and 8% w/w) increased the pH and conductivity of the soils to undesirable levels, however, the appliction of low amounts favoured plant growth and improved yields. Although the elements, viz. Cd, Cu, Fe, Mn, Ni and Pb accumulated in larger quantities in plants grown in fly-ash-amended soils than the control, their levels remained well below the threshold limit and, thus, are suitable for human consumption at the lowest fly-ash application rate. The increase in the sugar content at the low flyash application rate in beet root, the second most important crop for sugar extraction, enhances the possible use/application of fly-ash in tested amounts, in improving crop yields.

Response of Calendula officinalis L. to long-term fumigation with SO2

Abstract Seedlings of Calendula officinalis L. (30-days old) were raised in 1 m 2 plots and fumigated with 1 and 2 μg litre −1 SO 2 on alternate days. Analysis of plant samples collected at pre-flowering, flowering and post-flowering stages showed that photosynthetic pigments were degraded and leaf extract pH and protein content declined in SO 2 treated plants. In addition, scanning electron microscopic studies revealed that SO 2 stimulated the widening of stomatal pores in fumigated plants.

Monitoring of auto exhaust pollution by roadside plants.

The changing levels of SO2 and Pb in the air and vegetation, along ten road transections of Lucknow city (having varying traffic densities) have been investigated, with a view to authenticate a possible correlation between SO2 and Pb concentration in air and sulphate and lead accumulation in the foliage of avenue trees. The study showed that the road transection at Alambagh (traffic density 4835 for 2 h) revealed the highest level of pollutants (SO2, 202 µg m−3; SPM, 1080 µg m−3; and lead, 2.96 µg m−3, 2 h average) in air, as well as in the foliage of plants, whereas the road stretches with less traffic density correspondingly showed lower levels of pollutants. Pb and sulphate in leaves were found to be positively correlated with Pb and SO2 pollution in the air. Results suggest that Dalbergia sissoo and Calotropis procera are the ideal plant species to monitor as indications of Pb and SO2, respectively, in the air.

Effect of diesel exhaust pollution on cuticular and epidermal features of Lantana camara L. and Syzygium cuminii L. (Skeels.)

Abstract Cuticular and epidermal features of leaves of two common plant species namely, Lantana camara L. and Syzygium cuminii L. (Skeels.), growing in polluted and healthy (control) environments were studied under light and scanning electron microscopes. Polluted leaf samples were collected from the plants growing near a diesel generating set used in running a tube well. The study shows that in polluted populations of Lantana camara, the trichome frequency had increased four fold. In Syzygium cuminii, the stomatal openings were filled with dust and a tendency towards callus formation was also observed. The epidermal cells were comparatively thick walled and walls were broken at certain places. The changes observed in the cuticular and epidermal features of polluted populations of the investigated species indicate their significance as bioindicators of atmospheric pollution.

Foliar metal content and changes in epidermal traits of Lagerstroemia parviflora (L.) Roxb.

A comparative study of the physico-chemical properties of soil, leafmetal content and foliar surface traits in Lagerstroemia parviflora(L.) Roxb. plants, growing in an iron-rich mineralized and anon-mineralized area was carried out. Metal accumulation wasmaximum in summer; in the peak growing season, it declined duringthe rainy season but picked up again in winter. In leaves sampled froma mineralized region, epidermal cells were much smaller in size buthigher in number per unit area. Changes in the number and size of glandular papillae were also observed. Characteristic non-glandular,elongate trichomes with acute tip were also recorded in mineralizedpopulations. Scanning electron microscopic examination of the foliarsurface configuration revealed distortions in epicuticular wax structuresand wider cuticular striations with typically parallel arrangement inthese populations.The present study shows that high Fe-accumulation in leaves of L.parviflora during the exponential growth phase as well as changes inthe epicuticular structures may be indicators of metal stress in the populations of the mineralized area.

Growth responses of lycopersicon esculentum to cement dust treatment

Abstract Seedlings of Lycopersicon esculentum L. were raised in pots in December, 1989. When they attained 4–6 leaf stage, the seedlings were sprayed with cement dust at three different rates, i.e., 3 (L1), 5 (L2) and 7 (L3)g m‐2 d‐1 till 90‐day‐age of the plants. Dusted plants showed a consistent reduction in growth and yield. Photosynthetic pigments and phytomass of dusted plants were also reduced significantly. Flowering and fruiting processes were hampered by cement particles, maximum being in L3, followed by L2 and L1 plants. Ascorbic acid content of fruits was increased in treated plants.