dust loadings on some common plants near lucknow city

Environmental Pollution (Series B) 9 (1985) 71-80

Dust Loadings on Some Common Plants Near Lucknow City*

Mohd. Yunus, A. K. Dwivedi, K. Kulshreshtha & K. J. Ahmad

Plant Anatomy Laboratory, National Botanical Research Institute, Lucknow 226 001, India

ABSTRACT

Eightplant species--Acacia melanoxylon, Bauhinia malabarica, Bougain- villea glabra, Calotropis procera, Catharanthus roseus, Eucalyptus globulus, Ipomoea fistulosa and Peltophorum pterocarpum--were collected from a newly established suburb colony of Lucknow city, where the major pollutant is dust, to study the dust cleansing efficiency of the plant canopy and also to establish the correlation between the leaf morphological characteristics and their dust trapping potential. The dust load, in milligrams per square centimetre of leaf surface, was measured and related to foliar epidermal and cuticular characteristics, and morphological features.

INTRODUCTION

The use of vegetation in filtering out the dust, soot and particulates from the atmosphere has long been accepted and is common practice in some developed countries. Meetham (1964) quoted an exarople of 27 °/ / o

reduction of dust particles in London (Hyde Park) by a green area of only one square mile (2.5 km2). The planting of greenery (trees and shrubs) in Russian cities was recommended as a way to combat dust pollution. Novoderzhkina et al. (1966) reported a reduction in dust fall (2-3 times) by planting an 8-m wide green belt between the street and widely spaced buildings. Dochinger 0980), who examined the ability of plants to abate

* NBRI Research Publication No. 229 (N.S.).

71 Environ. Pollut. Ser. B. 0143-148X/85/$03.30 © Elsevier Applied Science Publishers Ltd, England, 1985. Printed in Great Britain

72 Mohd. Yunus, A. K. Dwivedi, K. Kulshreshtha, K. J. Ahmad

particulate pollutants, reported a reduction of up to 42 ~o in overall dust- fall by a canopy of coniferous plants in the urban areas of Ohio, USA. An interesting study was made by Bach (1972), who studied the dust- collecting potential of some plant leaf surfaces. In India, some initial studies have been carried out in Bombay by Shetye & Chaphekar (1977) and, in Calcutta, by Das (1981).

However, our present-day knowledge about the nature and extent of particulate or dust capture by plants is still very deficient. The present work was planned to examine the effect of inherent leaf morphological traits and their dust-collecting potential in the Lucknow environment.

MATERIALS AND METHODS

Description of site, climate and dust sampling

The area chosen for the present investigation lies in a newly established residential colony, Kurmanchal Nagar, in the suburb of Lucknow city, India. This colony is situated on the bank of a culvert and surrounded by agricultural fields. The soil is sandy and the climate monsoonic, with extremes of temperatures. Data on wind velocity, rainfall and total dust- fall are given in Tables 1 and 2. Wind speed and the amount of dust vary with season, the maximum generally being during April and May. Total

TABLE I Climatological Data for Lucknow City Showing Variations in the Wind Velocity and Rainfall during the Sampling Period

(April-June 1981)

Months Wind velociO' Rain[all (kmh l) (mm)

0830 h 1730 h

April 8.86 9.60 10.6 (2 24) (0-26)

May 14.32 15.22 5.9 (4-30) (0 36)

June 5-12 15.86 230.8 (5 36) (4 40)

Dust collection hy plants

TABLE 2 Estimates of Dust-Fall during April-June

1981

Months Open ,field Plant canopy Metric tonnes kin-2

April 40.6 30.8 May 49.8 38.3 June 36.2 24.1 Total 126.6 93.2

73

dust was sampled from both open field and the closed canopy of plants (40 x 40m 2) during the three-month period April-June 1981. For dust estimation, open top cylindrical buckets were used and values expressed in metric tonnes per square kilometre.

Collection of plant material

Fully mature leaf samples from eight plant species--Calotropis procera R.Br. (herb); Bougainvillea glabra Choisy, Catharanthus roseus L. and Ipomoea [istulosa Mart. ex Choisy (shrubs); Acacia melanoxylon R.Br., Bauhinia malabarica Roxb., Eucalyptus glabra Labill. and Peltophorum pterocarpum D.C. (trees)--growing in a closed canopy of almost 40 x 40 m 2 were collected. Foliar samples from the east, west, north and south sides and also from different heights of the plant were carefully collected on tracing paper. Leaves were then washed thoroughly, with the help of a camel hair brush and jet of water, in pre-weighed 250-ml beakers. The water was then completely evaporated in an oven at 100 °C to determine the total dust-load of each plant.

Leaf area was calculated using transparent graph-paper. For light microscope studies, epidermal peels of the upper and lower epidermidis were prepared following the method of Ahmad (1974). Leaves were cleared in lactic acid in order to study the vein-islets.

Preparation of material for SEM study Small strips (c. 0.5 cm square) were trimmed from the leaf areas between the tip and base and halfway between the margin and midrib, using freshly collected leaves. The material was dehydrated through ethanol series (from 30 ~o to absolute).

74 Mohd. Yunus, ,4. K. Dwivedi, K. Kulshreshtha, K. J. Ahmad

Foliar strips were then dried in a critical point drier using liquid CO2. After critical point drying, small pieces of leaf, about 0.25 cm square, were cut from the strips. Two pieces of material, one with the abaxial, and the other with the adaxial, surface upwards, were mounted side by side on the specimen stubs using double-sided adhesive tape.

Specimens were then coated with a thin film of gold (about 200 A) in an ion sputter coater. Coated specimens were examined with a JEOL-JSM 35C scanning electron microscope at an accelerating voltage of 10 kV, a tilt of 30 o incident to the electron beam and at an aperture of 100 #m. The image was observed at a magnification range from 200 to 5000 and photographs were taken on Superpan Agfa 120 roll film.

Care was taken to avoid any mechanical damage to the cuticle surface. The interval between removal of specimens from the plants and examination in the scanning electron microscope was kept to a minimum for the study of wax on the leaf surface.

OBSERVATIONS

Morphology and orientation of leaf

Acacia melanoxylon--Phyllode oblanceolate to lanceolate, usually one edge straight and the other curved, 3-6 parallel veins, reticulately veined in between (Fig. ld). Phyllode area: 24 cm 2. Orientation: > 90°, drooping nature. Bauhinia malabarica--Leaves broader than long with two obtuse lobes reaching about one-third of the length, slightly cordate, glabrous and glaucous beneath, 7-9 nerved (Fig. lc). Leaf area: 36 cm 2. Orientation: < 90 o. Bougainvillea glabra--Leaves glabrous or subglabrous, lanceolate, broad, ovate, ovate-oblong. Leaf area: 17cm 2. Orientation: < 90 °. Calotropis procera--Leaves sessile, thick, glaucous-green, 10-20cm long, elliptic or obovate-long, acute or shortly acuminate with a narrow cordate, or often amplixicaul, base (Fig. l a). Leaf area: 70 cm 2.

Fig. I(a~l). Leaves with dust loads, a. Calotropts procera, b. lpomoea fistulosa, c Bauhinia malabarica, d. Acacia melanoxylon.


Fig. 2(a--e). Scanning electron micrographs of foliar surfaces, a. Upper surface of Calotropisprocera with dust load ( x 500). b. Same surface, after dust removal, with long velvety trichomes ( x 270). c. Upper surface of lpomoea fistulosa, surface striated with non-glandular trichomes ( x 420). d. Lower surface of Bauhinia malabarica, showing wax deposition x 750). e. Upper surface of Catharanthus roseus, surface smooth ( x 1570).

Orienta t ion: < 90 o or a lmost 90 °, i.e. hor izonta l to g round level. Catharanthus roseus--leaves opposi te , entire, deep green, obova te or oblong, small in size. Lea f area: 6 c m 2. Or ienta t ion: < 90 ° or a lmost 90 °. Eucalyptus globulus--Leaves usually opposi te , simple, most ly entire, cor iaceous , st ipulate, lanceolate in shape. Leaf area: 3 3 c m 2. Or ienta t ion: > 90 o, d roop ing nature. Ipomoea fistulosa--Leaves 6 - 2 0 c m long, ovate to ova te -ob long , acumina te at apex (Fig. l b). Leaf area: 9 2 c m 2. Or ienta t ion: < 9 0 ° or a lmost 90 ° , i.e. hor izonta l to g round level, excepting the tip region which shows or ienta t ion > 90 °.

. :N

Dust collection by plants 77

Fig. 2.--contd.

Peltophorum pterocarpum--Leaves distinctly petioled, 15-30 cm long, pinnae opposite; leaflets, 16-30, close ligulate-oblong, sessile, obtuse, unequal-sided 1.25-2 cm long, rigidly subcoriaceous. Leaflet area: 12cm 2. Orientation: <90 ° .

Epidermal and cuticular characteristics

Epidermal and cuticular characteristics are summarised in Table 3. The morphology described here pertains to the upper surface except in the case of Bauhinia malabarica, where the lower surface is described. Acacia melanoxylon--Surface smooth; trichomes absent; number of vein-islets poor as venation is parallel. Bauhinia malabarica--Surfaces covered with wax blooms (Fig. 2d); trichomes tubercled, 293 #m long, strigose; vein-islets, thirty per square millimetre. Bougainvillea malabarica--Surface smooth; trichomes smooth-walled, cylindrical, 150#m long; vein islets, seven per square millimetre.


TABLE 3 Leaf Area, Epidermal Characteristics and Total Dust Load

Plant name Leaf area (cm 2 )

Epidermal characteristics

Trichome Trichome Vein-islets frequency size per square per square (#m ) millimetre millimetre

Total dust load

(rag cm- 2)

Calotropis procera 70 47 226 65 8.81 Ipomoea fistulosa 92 19 34 38 3.27 Peltophorum pterocarpum 12 b 40 66 43 1'86

Catharanthus roseus 6 - - - - 24 1.41 Bougainvillea glabra 17 15 156 7 1.15

Bauhinia malabarica ~ 36 32 293 30 0.96 Strigose

Eucalyptus globulus 33 - - - - 8 0.55 Acacia melanoxylon c 24 - - - - Parallel 0.53

venation

° Excepting Bauhinia, the epidermal characteristics are of the adaxial surface. Leaflet area.

+ Phyllode area.

Calotropis procera--Surface striate, covered with a dense population of velvety trichomes (226#m long) (Figs 2a,b); vein-islets, sixty-five per square millimetre. Catharanthus roseus--Surface smooth (Fig. 2e); trichomes absent; vein- islets, twenty-four per square millimetre. Eucalyptus globulus--surface smooth; few blooms of wax present on the surface; trichomes absent; vein-islets, eight per square millimetre. Ipomoea fistuiosa--Surface striate (Fig. 2c); trichomes smooth-walled, cylindrical, 34/zm long; vein-islets, thirty-eight per square millimetre. Peltophorum pterocarpum--Leaflet surface smooth; trichomes tubercled, 66 ttm long; vein-islets, forty-three per square miUimetre.

Higher amounts of dust-fall were recorded from the open field. In the planted area the overall movement of particulates was reduced to 26 % (Table 2).

Results of the dust load per square metre of leaf surface are given in Table 3. It was found that of the eight plants studied, Calotropisprocera collected the maximum amount of dust (8.81 mgcm-2), followed by

Dust collection by plants 79

Ipomoea fistulosa (3-2757mg), Peltophorum pterocarpum (1.8637mg), Catharanthus roseus (1-4105mg), Bougainvillea glabra (1.1464mg), Bauhinia malabarica (0.9656 mg), Eucalyptus globulus (0.5498 mg) and Acacia rnelanoxylon (0.5311 mg).

DISCUSSION

The results of the examination of the leaf morphology indicate a convincing relationship between inherited morphological traits and the amount of dust captured. Calotropis procera, with a large leaf size (70cm 2) collects the maximum amount of dust (8.81 mg cm-2). On the other hand, Eucalyptus globulus and Acacia melanoxylon, both with an oblanceolate to lanceolate shape, collect the minimum amount of dust, i.e. 0.54 and 0.53mg cm -2, respectively. It is apparent that various morphological features, alone or in combination, are et~cient in the interpretation of air particulates. These characteristics are: orientation of the leaf on the main axis, size (leaf area in square centimetres) and shape, surface nature (smooth/striate), the presence or absence of trichomes and wax deposition, etc. Some earlier reports (Shetye & Chaphekar, 1978; Das, 1981) also support the correlation established by us regarding the dust-capturing potential and morphological characteristics.

Studies of particulate or dust filtration by plants in particular, and the r61e of plants in mitigating air pollution (gaseous) in general, involve an evaluation of a number of factors:

The quantitative potential of plants to reduce ambient particulates. The arrangement, nature and location of trees and their effect on dust filtration. Variation in leaf morphology in such matters as leaf size or leaf area, shape and orientation, etc. Epidermal characteristics such as the presence or absence of trichomes, trichome type, stomatal movement, venation type and number of vein-islets. Cuticular configuration--smooth or striate, the presence or absence of wax, the type of wax bloom and wax distribution on the leaf surface, etc. Chemical treatment of plants in order to measure, if possible, those morphological characteristics which could enhance the potential of leaves to absorb dust.


The ability of plants to intercept dust is demonstrated in the present paper. However, very little is known about the biotic controlling influences and a detailed study is called for in order to discover the correlation between the plant leaf structure and the magnitude of the captured dust. It is hoped that, eventually, it will be possible to recommend plants for use as screens or green belts in industrial areas and adverse urban locations in order to mitigate dust and improve air quality.

ACKN OWLEDGEM ENTS

We are indebted to Dr T. N. Khoshoo, Director, National Botanical Research Institute, Lucknow, for providing the necessary facilities. For technical assistance the authors are grateful to Mr D. B. Shukla. Two of us (A.K.D. and K.K.) thank the Council of Scientific and Industrial Research, New Delhi, for the award of a Senior Research Fellowship.

REFERENCES

Ahmad, K. J. (1974). Cuticular studies in some Nelsoniodeae (Acanthaceae). Bot. J. Linn. Sot., 68, 73-80.

Bach, W. (1972). Atmospheric pollution, New York, McGraw-Hill. Das, T. M. (1981). Plants and pollution. Presidential address, Section of

Agricultural Sciences," 68th Session, Indian Scientific Congress, Varanasi, 1 17.

Dochinger, L. S. (1980). Interception of airborne particulates by tree plantings. J. environ. Qual., 9, 265-8.

Meetham, A. R. (1964). Atmospheric pollution." Its origin and prevention. Oxford, Pergamon Press.

Novoderzhkina, Yu, G., Andrianova, L. A. & Zheldakkova, G. G. (1966). Effect of plantings on the sanitary and hygienic conditions of densely populated settlements. In AICE survey of USSR air pollution literature, ed. by M. Y. Nuttonson, Vol. 2, 25-31, Silver Spring, Md, American Institute of Crop Ecology.

Shetye, R. P. & Chaphekar, S. B. (1977). An inexpensive method for the determination of airborne dusts. Proc. Seminar on man and his environment, Bombay, Institute of Science, 6 October, 1976, 85-90.

dust loadings on some common plants near lucknow city

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