OZONE FUMIGATION ACCELERATES SURFACE EROSION ON NORWAY SPRUCE NEEDLES Ka tinka Ojanperij and Satu Huttunen•

Universi ty of Gothenburg , Department of Plant Physiology , Carl Skot t s­

bergs Ga ta 2 2 , S-4 1 3 1 9 Gothenburg , Sweden

University of Oulu , Department of Botany , SF-9 0 5 70 Oulu , Finland*

ABSTRACT

Ozone exposed needles of the Norway spruce were s tudi ed wi th an SEM in order to detect pos sible ozone induced changes in the surface struc ture of the needle s . The needles were obt a ined from two experiment s carried out in summer s 1 9 8 5 and 1986 . Spruce seedlings were exposed in open- top-chambers to 0 , 1 00 , 200 and 300 ug ozone / m3 air during weekdays . Acce lerated sur face erosion could be observed around the s tomata , tha t wa s s t a t i s t ically s l i ghtly s igni fican t ( p=0 . 0446 ) . The tubular wax crystal loids of around the s tomata of ozone fumi ga ted needles were more often flat and sol id than in the control ma teria l . The sma l l wax crys tals covering the eroded area , tha t seemed newly crys tallized were characteristic for thi s injury type . In addi t i t ion , s toma ta or nonstoma ta related insec t injurie s , caused by smal l needle decaying mi tes , were observed in the needle s . The injury was present in all sample s , but was mos t intense in the needles fumiga ted wi th higher ozone concentrat ions .

INTRODUCTION

The plant sur face i s the interface be tween the p l ant and i t s environment . The cuticle covered by inert layer of epicuti cular wax prote c t s the plant from unfavourable condi t ions such as fros t , drought , radiat ion and the various pa thogens . It also acts as a main barrier to air pol lutants ( Jeffree 1 9 86 ) . The wax p l'ugs covering the s tomata especially are effec t i ve ant i transpirants reducing the rate of s toma t a ! t ranspira tion by two thirds ( Je ffree 1 9 7 1 ) .

The epicuticular wax of current needles of Norway spruce consist of small tube s forming evenly di spersed wax s t ruc ture . As a r e sult of natur a l erosion in the needles , the wax tubes agglomerate firs t forming a reticulate and then a p l a t e l ike wax struc ture ( Sauter and Vos s 1 9 8 6 ) . The lifespan o f heal thy needl e s of Norway spruce varies from 7 to 1 4 years ( Gunthardt and Wanner 1 9 8 2 , Karhu & Hut tunen 1 9 8 6a ) .

Exposure to air pollutan t s i s known to alter the s t ructure of epicuticular wax, resul t ing in erosion and s toma ta! occ lusion . For i n s t ance , the eros ion of epicuticular wax

490

of Pinus sylve stris needles , caused by air pol lution , was observed to be faster than the normal erosion due to ageing (Hut tunen & Laine 1981 , 1 983 , Cros sley & Fowler 1 9 86 ) . Thi s s tudy was under t aken to s tudy whe ther or not ozone i s also a fac tor which induces change s i n the sur face s t ruc ture of Norway spruce needle s .

MATERIAL AND METHODS

The ozone fumiga ted needles of Norway spruce were ob tained from two different experiment s carr ied out in the summer s 1 9 8 5 and 1986 by Dr . J . B . Bucher , at the Swi s s Federal Ins titute of Forestry Research in Birmensdor f , Swi tzerland .

At 1 9 8 5 the material used was needles of 4-year old graft ings of mature spruce tree that were treated wi th charcoal filtered air or charcoal f i l tered air with 300 ug ozone / m3 air , 9 h/ day on 1 1 4 workdays . The material used at 1986 was treated wi th charcoal filtered air or charcoal filtered air + 200 ug ozone / m3 air , 9 h/ day on 109 workdays . From each treatment 2 5 current needles were analyzed .

Needle samples were air dried at room temperature and s tored in paper bags unt i l the microscoping was done . Air dried samples were sputter coa ted wi th thin ( 4 5 nm) gold-palladium film using Polaron 5 1 00 sputter equipment . Coated samples were s tudied with a JEOL JSM- 3 5 scanning electron microscope ( 1 5 kV accel erating vol tage , sample current 1 0-1 1 A , exposure t ime 1 00 s . )

Diffe rent types of injuries observed during scanning electron microscopy were classified into two groups ( injury observed/

not observed ) , using SEM-migrographs 7 8-1 00 x, 400 x , 1 000 x, 10 000 x/sampl e ) .

Clas s i fied micrograph material was statistically analyzed wi th an IBM-computer using a two-way- frequency table ( BMDP P4F­

programme ) . Each symptom was separately cross­

tabulated wi th the ozone treatment . The statistical ana lysis used in the programme , was the non-parame trical l ikelihood-ratio chi­

square t e s t .

40 30 20 10

D

IZZI ^INJURED

3

Fig. 1. Stamata of healthy current year needle. Mag. 440 x. Clean air. Fig. 2. Stomata of ozone fumigated needle.

(³00 ug / m³ air). Mag. 440 x. Fig. ³. Frequences of healthy and injured needles in control and ozone treatments (200 and ³00 ug ozone /m³ air).

RESULTS

When s tudying the needles from two different experiments a very s igni ficant di fference ( p< 0.0001 ) in the condition of the surfa ce waxe s be tween the needles of two spruce c lone s used wa s observed. The needles of the s pruce clone used in 1 9 86 contained much more crys talloid wax than needles of the spruce c lone used in 1 9 8 5.

The genera l image of needles from the 1 9 8 5 experiment revealed a flat and smooth s truc ture of surface waxe s when compared wi th the needle s of open field ( Karhu & Hut tunen 1 9 86a ) . The needles from the 1 9 86 experiment did no t have thi s kind of erosion be tween the s t oma ta!

areas.

When s tudying the effects of ozone fumiga tion , a sligthly significant change could be de tec ted in the stoma ta. Tubular wax crys tal loids covering the stoma ta were more often flat and solid under ozone exposure. The change was observable at the edge s of The s toma ta ( p=O. 0446 ). The small wax tubes covering the eroded area tha t seemed newly crys tallized were typical of thi s injury type ( Figs. 1 and 2 ) .

In addi ti tion , the insect injuries detec ted in the needles seemed to corre spond to exposure to higher ozone concentra tions.

Injurie s were pre sent in all the samples but were mo s t intense in samples fumigated wi th ozone. The experiment was not , however designed to t e s t thi s , as all the plants of one treatment were all in the one and same chamber.

The observed effect could be a chamber effe c t o r clone effect or a coincidence. Gunthard t­

Goerg & Keller ( 1 9 8 7 ) did not have any infe c t ion in their s tudies in the same experiment. The frequences of the injuries observed in the migrograph ma terial are presented in the fi gure ³.

DISCUSSION

Air pol lut ion , especially S-compounds , i s known to alter the morphological s truc ture and the chemi cal composit ion of epicuti cular waxe s of coni fers ( Cape & Fowler 1 9 81 , Hut tunen &

Laine 1 9 8 1 , 1 9 8³, Cape 1 9 8³, Cross ley & Fowler 1 986 , Schmi t t et al. 1 9 8 7 ). Also natural erosion due to ageing causes chemical and

morphological change s in the epicuticular waxe s of the needles ( Hut tunen & Laine 1 9 8³, Gunthardt -Goerg 1 9 86.)

Eros ion of the epicuticular wax , both natural and tha t caused by air p o l lution , probably increases cuticular transpira t i on ( Cape & Fowler 1 9 8 1 ) and accelera t e s wint er desiccation and needle shedding ( Lewi t t 1 9 8 0 , Hut tunen & Laine 1 9 8³). Structural degrada t i on of epis toma tal wax crystalloids caus e s s t oma ta!

occlusion and potentially inhibi t s s t oma tal transpira t ion , which o f course has far reaching physiological consequences on tree s ( Sauter &

Vos s 1 98 6 ) . De spite many ozone fumiga t i on experiment s carried out in the l a s t two decade s , l i t t l e informa tion has been publi shed about the e ffec t s of ozone on the the epicuticular waxe s of the conifers.

In an experiment carried out by Trimble e t al. ( 1 9 81 ) , n o erosion caused b y ozone could be observed with SEM on the needles of Pinus s trobus. The authors , however , found di fferences in the chemi cal wax comp o s i t i on of ozone- sensi tive and - tolerant clones o f Pinus strobus. S ince the fumiga t ion time in the experiment was very short ( 1 wk ) compared wi th the needle age (which is several years ) , the fac t tha t no erosion could be observed after the experiment was not surprising.

Gunthardt-Goerg and Keller ( 1 9 8 7 ) observed some flat tened areas wi th fused wax fibr i l s bo th in control and ozone fumigated ( 1 3 5 days ) needles. They could not , however , observe any difference s in the epicuticular waxe s be tween ozone fumiga ted and the control samp l e s. They used different spruce clone and freeze-drying prepara tion me thod , but the experimen t was the same as the 1 9 8 5 one.

In the long-term ( 2 , 5 year ) fumi g a t i on and simulated acid rain experiment carried out by Schmi t t e t al. ( 1 9 8 7 ) ozone was no t found to increase the ero s ion o f the epicuticular wax o f fir and spruce needles. A c i d rain , however , caused s evere surface eros ion which wa s very much l ike tha t observed in our s tudy.

The ozone concentra tion used in the experiment carried out by Schmi t t et a l.

( 1 9 8 7 ) was too low ( 1 00 ug ) t o cause signi ficant erosion in the material ana lyzed in our s tudy. Higher ozone concentra tions ( 200 and

300 ug / m³) increased the surface ero s i on in

the material analyzed in our s tudy . Magel &

Ziegler ( 19 8 6 ) found wax plug dis turbancies in current needles of Picea abies after ozone and acid rain treatment . Since ozone concentrations o f up to 1 80-1 90 ug / m3 are known to be purely coincidental , since infec ted seedlings can e a s ily be put in the fumiga tion chambers . weathering of Scots pine epicut icular wax in polluted and clean air. New Phytol . pollutan t s . Archiwum Ochorony Srodowiska 2-4 , 29-38. antechamber of Sitka spruce effe c t s on water vapour and

Fors twis sens chftliches Centralbla t t 105 ( 4 ) : 234 -238.

Untersuchungen an S tomata von Fichten- und Tannennadeln nach Bega sung und saurer Beregnung . Eur . J. For. Pa th. 1 7 : 149-1 5 7 . Tre show , M . ( Ed . ) . 19 84. Air Pollution and

Plant life. John Wi ley and Sons Ltd . 486 Trimble , J . L . , Skelly , J.M. , Tolin , S.A . and pp.

Orcut t , D . M. 1 981. Chemical and Ultrastruc tural charac terisat ion of the needle epicut icular wax of two clones of Pinus s trobus differing in sens itivity to ozone . Phytopathology 7 2 : 6 5 2-6 5 6.

UBA (Umweldtbunde samt ) ( 1 9 8 5 , 1986 ). Mona t s­

berichte aus dem Me s sne tz.

Air Pollution and Forest Decline (J. B . Bucher and I . Bucher-Wallin, eds.).

Proc. 1 4th Int. Meeting for Specialists in Air Pollution Effects on Forest Ecosystems, IUFRO P2.05, Interlaken, Switzerland, Oct . 2-8, 1 988 . Birmensdorf, 1 989, p. 493-495.

EFFECT OF SIMULATED ACID RAIN ON FOLIAR UPTAKE OF Rb⁺ AND so!­

BY TWO CLONES OF SITKA SPRUCE ( PICEA SITCHENSIS ( BONG , ) CARR, )