Wind Breaks

8/2/2019 Wind Breaks

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R E S E A R C H N O T EI N F L U E N C E O F W I N D B R E A K S A N D C L I M A T I C R E G I O N O N

D I U R N A L F L U C T U A T I O N O F L E A F W A T E R P O T E N T I A L ,S T O M A T A L C O N D U C T A N C E , A N D L E A F T E M P E R A T U R E O F

G R A P E V I N E SBrian M. Freeman, W. M. Kliewer, and Peter Stern

Respectively, Graduate Student and Professor of Vi t icul ture, Department of Vi t icul ture andEnology, Un iversity of California, D avis; and Winemaker, T urgeo n & Lohr Winery, San Jose, C A .Manuscript submitted 9 November 1981.Revised m anuscript received 22 February 1982.Accepted for publ ication 24 May 1982.

A B S T R A C TReduced stomatal conductance of Chardonnay grape-vines grown near Greenfield in the Salinas Valley wasassociated with both dense fog during most of the morn-ing and then with wind in the afternoon. After 13:00hours, when wind speed markedly increased in the Green-field area, vines grown in the absence of a windbreak had

markedly lower stomatal conductance than vines protect-ed by a windbreak. Wind did not appear to increase waterstress of non-sheltered vines, which were less stressed(less negative leaf water potential) than sheltered vines(more negative leaf water potential), indicating that thereduced stomatal conductance of non-sheltered vines wasnot due to water stress. Leaf stomatal conductance

remained high at Davis for about 12 hours per daycompared to four and eight hours for non-sheltered andsheltered vines grown near Greenfield. Since stomatalconductance, CO2 assimilation, and rate of photosynthe-sis are directly related, low stomatal conductance indi-cates that C02 assimilation and photosynthesis are beingcurtailed. Consequently, non-sheltered vines located inthe more windy areas of Salinas Valley may be photo-synthetically active for as little as four hours per day,whereas the photosynthetic active period of vines grownin the presence of windbreaks ma y be nearly doubled. Theeffects of reduced photosynthetic activity on grape qual-ity is discussed.

Stomatal regulation is a complex interaction of exter-nal and internal factors (1,5). In many plants wind cancause stomatal closure and co nsequently l imit CO2 uptakeand photosynthesis, even though adequate soil moistureis available.During most of the summer months, the SalinasValley is characterized by daily winds that begin blowingin from the ocean during the late morning or earlyafternoon hours and generally continue late into thenight. These winds coupled with dense morning fog verylikely reduce the daily period for active CO2 uptake andassimilation in grapevines growing in parts of the SalinasValley as well as other areas wi th similar climatic charac-teristics.To investigate this climatic condition, a series ofmeasur ements were made on 11 August 1981 to comparechanges in stomatal conductance and leaf water relationsof Chardonnay grapevines growing in sheltered (behind

windbreaks) and non-sheltered sites near Greenfield,California. Similar meausrements were made on Carig-nane vines grown at the University of California Experi-mental Vineyard at Davis on 19 August 1981. Tempera-ture conditions were mild at Davis on this day, with adaytime maximum temperature of 27C compared to26C at Greenfield on August 11. The Greenfield area is aRegion II and Davis is a Region IV according to theWinkler- Amerine degree day system of classifying climat-

ic regions in California.The main objective of this investigation was to evalu-ate the relative importance of windbreaks on diurnalfluctuations of leaf temperature, stomatal conductance,

and leaf water potential of grapevines.M A T E R I A L S A N D M E T H O D SStomatal conductance and temperature were mea-sured on the abaxial surface of leaves at one to two hourintervals from about 06:00 to 20:00 hours with a Li-CorLi-65 Autoporometer (Li-Cor Instrument Corp., Lincoln,Nebraska). Leaf water potential was measured with aportable pressure chamber, Model 600 (PMS InstrumentCo., Corvallis, Oregon) using 30 second interval readings,and average wind speed was measured with a handheldanomometer. Data presented in Figures 1 to 4 are themeans of three measurements. Exposed, fully expandedleaves, about the 15th leaf from the base of the shoot,

were selected for measurements.The Greenfield site was located on the Turgeon &Lohr Vineyard, two kilometers northwest of Greenfield.The sheltered site vines were located 70 meters from anapproximately 20 meter high eucalyptas tree windbreak.The non-sheltered site (no windbreak trees) was in thesame block of vines, but about 400 meters east of thesheltered site and 160 meters from the north edge of thevineyard. The variety at both these sites was Chardon-233

A m . J . E n o l . V i t i c . , V o l . 3 3 , N o . 4 , 1 9 8 2


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1 . 2n a y , w h i c h w a s h e a d - t r a i n e d a n d c a n e - p r u n e d o n a t h r e e -wi re ve r t i c a l t re l l i s cons i s t i n g o f a cane w i re 107 cm f romt h e g r o u n d a n d t w o f o li ag e s u p p o r t i n g w i r e s 3 0 a n d 6 0 c mabove t he cane wi re .T h e D a v i s s i t e w a s l o c a t e d a t t h e U n i v e r s i t y o fC a l i f o r n ia E x p e r i m e n t a l V i n e y a r d a n d c o n s i s t e d o f e i g h t -y e a r - o l d C a r i g n a n e v i n e s c o r d o n - t r a i n e d a n d s p u r p r u n e don a t h ree -wi re t r e l li s cons i s t i ng o f a co rdo n wi re 107 cmf r o m t h e g r o u n d a n d t w o f o li a ge s u p p o r t i n g w i r e s o n a 9 0c m w i d e c r o s s a r m 4 5 c m a b o v e t h e c o r d o n w i r e .

R E S U L T SL e a f t e m p e r a t u r e s o f v i n e s g ro w n a t D a v i s a n d s h e l -t e red v ines a t Greenf i e ld (F ig . 1 ) d id no t d i f f e r s i gn i f i -can t ly a t 08 :00 hours ; howeve r , a t Greenf i e ld t e r~pe ra -t u r e s o f le a v es f r o m n o n - s h e l t e r e d v i n e s w e r e 0 . 8 C l o w e rt h a n s h e l t e r e d le a v es a t 0 8: 0 0 h o u r s ( P < 0 . 0 1 ) . M a x i m u m

l e a f t e m p e r a t u r e s a t G r e e n f i e l d a n d D a v i s w e r e r e a c h e d a t13 :00 and 15 :00 hours , r e spec t i ve ly , and d id no t d i f f e rs i g n i f i ca n t l y ( F ig . 1) . M a x i m u m t e m p e r a t u r e s o f n o n -she l t e red v ine l eaves a t Greenf i e ld we re abou t 1C lowert h a n s h e l t e r e d l e a v e s , n o t s i g n i f i c a n t l y d i f f e r e n t a t t h e5% l eve l . La t e a f t e rnoon (17 :00 t o 18 :00 hours ) non-s h e l t e r e d l e a f t e m p e r a t u r e s a t G r e e n f i e ld w e r e s i g n i f i-c a n t l y ( P < 0 . 0 0 1 ) l o w e r t h a n l e a f t e m p e r a t u r e s a t D a v i smea sured a t t he sam e t ime o f t he day . Al so , l a t e a f t e r -n o o n e x p o s e d l e a f t e m p e r a t u r e s o f s h e l t e r e d v i n e s a tG r e e n f i e l d w e r e a b o u t 2 C w a r m e r t h a n n o n - s h e l t e r e dl eaves (P


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INFLUENCE OF WINDBREAKS - - 235

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T I M E ( h r s )Figu re 4 . D iu rna l changes i n l ea f wa te r po ten t i a l o f Chardonnayv ines g row n a t G reen f i e ld und er she l te red (11 ) and no n-she l te red(El ) cond i t i ons , and Car ignane v ines g row n a t Dav i s (A) .

d a t a i n F i g u r e 4 r e v e a l s t h a t t h e w i n d d i d n o t c a u s es t o m a t a l c l o s u r e i n d i r e c t l y t h r o u g h i n c r e a s e d t r a n s p i r a -t i on , and hence wa te r s t r e ss i n t he v ines , s i nce t he l e a fw a t e r p o t e n t i a l o f t h e n o n - s h e l t e r e d v i n e s w a s h i g h e r( le s s n e g a t iv e ) t h a n t h e s h e l t e r e d v i n e s . T h e w a t e r p o t e n -t i a l o f v i n e s i n b o t h s i t es d e c l i n e d a s t h e d a y p r o g r e s s e d ,a s is n o r m a l l y t h e c a s e ( 6) . W h e n t h e s t o m a t a o f t h e n o n -she l t e red v ines we re nea r ly c losed (abou t 14 :00 h r ) t hel ea f w a t e r p o t e n t i a l r e m a i n e d n e a r l y c o n s t a n t a t a b o u t - 8b a r s u n t i l a r o u n d 1 7 : 0 0 h o u r s . B e t w e e n 1 5 : 0 0 a n d 1 8 : 0 0h o u r s t h e l e af w a t e r p o t e n t i a l o f th e s h e l t e r e d v i n e s w a ss i g n i f i c a n tl y ( P < . 0 5 ) m o r e n e g a t i v e t h a n t h e n o n - s h e l -t e r ed v i ne s . A l ea f w a t e r p o t e n t ia l o f - 1 3 t o - 1 5 b a r s i sg e n e r a ll y c o n s i d e r e d n e c e s s a r y t o c a u s e s t o m a t a o f g ra p e -v ines t o c lose (4 ,6 ) . Th e w a te r po t en t i a l o f t he s he l t e redv i n e s c o n t i n u e d t o d e c l i n e u n t i l a b o u t 1 6 : 0 0 h o u r s , r e a c h -i n g - 1 1 b a r s , a t w h i c h t i m e t h e i r s t o m a t a b e g a n t o c l o s e ;i . e . s t oma ta l conduc t ance dec l i ned (F igs . 2 and 4 ) . Thus ,s t o m a t a l c l o s u r e i n t h e n o n - s h e l t e r e d v i n e s w a s n o ta t t r i b u t a b l e t o h i g h le a f w a t e r p o t e n t i a l s i n c e t h e - 1 3 b a rt h r e s h o l d l e v e l f o r s t o m a t a l c l o s u r e w a s n e v e r r e a c h e d .T h e r e f o r e , i t i s c o n c l u d e d t h a t s t o m a t a l c l o s u r e w a s ad i r e c t e f fe c t o f w i n d a n d n o t m o i s t u r e s t r es s .

D I S C U S S I O NS t o m a t a l c o n d u c t a n c e f o r w a t e r v a p o r i n l e a v e s( w h i c h i s w h a t t h e a u t o p o r o m e t e r m e a s u r e s ) i s a l s o a ne s t i m a t i o n o f CO 2 a s s i m i l a t i o n i n t o l e a v e s ( 5 ). C o n d u c -t a n c e o f w a t e r v a p o r a n d C O 2 i n t o t h e l e a f i n v o l v e s

i d e n t i c a l p a t h w a y s a n d d i f f u s i o n m e c h a n i s m s . W a t e rvapor , because o f i t s l ower molecu l a r we igh t d i f fuse s 1 .6t i m e s f a s t e r t h a n C 0 2 . T h e s e n s i t i v i t y o f a s s i m i l a t i o n a n dt r a n s p i r a t i o n r a t e s r e m a i n s c o n s t a n t w h e n s t o m a t a l c o n -d u c t a n c e i s v a r i e d b y c h a n g e s i n t e m p e r a t u r e a n d h u m i d -i t y ( 2 ). H o w e v e r , t h e r a t i o o f a s s i m i l a t i o n t o t r a n s p i r a -t i o n i s n o t c o n s t a n t u n d e r a l l c o n d i t i o n s ( 2) , c o n s e q u e n t l ys t o m a t a l c o n d u c t a n c e i s o n l y a g u i d e t o p o t e n t i a l C O 2u p t a k e .T h e h e a t s u m m a t i o n f o r b o t h D a v i s a n d G r e e n fi e ld o nt h e d a t e s t h a t m e s u r e m e n t s w e r e t a k e n w e r e s i m i l a r , s oa c c o r d i n g t o t h e W i n k l e r - A m e r i n e d e g r e e d a y s y s t e m t h e

a s s i m i l a t i o n s h o u l d h a v e b e e n s i m i l a r . T h e s t o m a t a lc o n d u c t a n c e d a t a s u g g e s t t h a t n o n - s h e l t e r e d v i n e s a tG r e e n f i e l d w e r e a s s i m i l a t i n g a t t h i s m a x i m u m r a t e f o ro n l y a b o u t f o u r h o u r s p e r d a y , w h e r e a s , v i n e s a t D a v i sc o n t i n u e d a t a m a x i m u m r a t e f o r 1 2 t o 1 3 h o u r s . T h em a x i m u m s t o m a t a l c o n d u c t an c e a t D a v i s w a s le ss t h a n a tGreenf i e ld , bu t t h i s may be due t o va r i e t a l d i f f e rences(1 ,3 ) o r l e a f age and p recond i t i on ing e f fec t s . Fog l im i t eds t o m a t a l c o n d u c t a n c e o f t h e G r e e n f i e l d v in e s d u r i n g m o s to f t h e m o r n i n g h o u r s , w h e r e a s , w i n d a p p e a r e d t o b e t h ed o m i n a n t f a c t o r in t h e a f t e r n o o n . T h e p r e s e n c e o f aw i n d b r e a k a t G r e e n f ie l d i n c r e a s e d t h e p e r i o d o f m a x i m a ls t o m a t a l c o n d u c t a n c e t o a b o u t e i g h t h o u r s c o m p a r e d t of o u r h o u r s f o r n o n - s h e l t e r e d v i n e s .

I n c r e a s e d l e a f t o a i r v a p o r p r e s s u r e d e f i c it r e d u c e ds t o m a t a l c o n d u c t a n c e a n d a l i n e a r r e l a t i o n s h i p w a s e s -t a b l i s h e d b e t w e e n s t o m a t a l c o n d u c t a n c e a n d l e a f t o a i rvapor p re ssu re de f i c i t fo r app l e s (8 ) . Th i s r e sponse i sa t t r i b u t e d t o e p i d e r m a l w a t e r l o s s a n d n o t a d e c r e a s e i nb u l k l e a f w a t e r p o t e n t i a l . V a p o r p r e s s u r e d e f i c it w a s n o tm e a s u r e d f o r t h e d a y s r e p o r t e d i n t h i s e x p e r i m e n t , b u tw i n d w o u l d r e d u c e v a p o r p r e s s u r e d e f i c i t a n d m a y h a v eb e e n t h e r e a s o n f o r t h e r e d u c e d s t o m a t a l c o n d u c t a n c e o ft h e n o n - s h e l t e r e d v i n e s .T h e l a t e t i m e i n t h e y e a r w h e n g r a p e s m a t u r e i n t h en o r t h e r n p a r t o f t h e S a l i n a s V a l l ey m a y b e i n l a rg em e a s u r e d u e t o b o t h t h e l i g h t l im i t a t i o n s o f f o g a n d w i n df a c t o r s t h a t g r e a t l y l i m i t t h e d a i l y a c t i v e p e r i o d o fp h o t o s y n t h e s i s n e e d e d t o m a n u f a c t u r e t h e s u g a r f o rf ru i t s .T h e r e d u c e d p h o t o s y n t h e t i c a c t i v i t y o f v i n e s g r o w n int h e S a l i n a s V a l l e y m a y a l s o i n d i r e c t l y a f f e c t p o t a s s i u mleve l s i n g rape be r r i e s . In an expe r imen t wi th Ricinus

communis L . , S m i t h a n d M i l b u r n ( 7 ) s t u d i e d p h l o e ml o a d i n g o f p o t a s s i u m a n d s u c r o s e . P o t a s s i u m w a s l o a d e di n t o t h e p h l o e m w h e n s u c r o s e w a s n o t a v a i l a b l e d u e to a ne x t e n d e d d a r k p e r i o d . P o t a s s i u m c o n c e n t r a t i o n i n t h ep h l o e m w a s i n c r e a s e d b y 3 0 % a n d 6 0 % a f t e r 1 2 a n d 2 4h o u r d a r k p e r i o d s , r e s p e c t i v e l y . T h e 2 0 h o u r p e r i o d i nw h i c h C 0 2 w a s n o t a c t i v e l y a s s i m i l a t e d i n n o n - s h e l t e r e dv i n e s a t G r e e n f i e l d m a y i n c r e a s e t h e p o t a s s i u m l e v e l i nt h e p h l o e m , w h i c h w o u l d t h e n b e a v a i l a b l e f o r l o a d i n gi n t o g r a p e b e r r ie s . I t i s u n k n o w n i f g r a p e v i n e s b e h a v es imi l a r ly t o Ricinus, a s a t t e m p t s t o o b t a i n u n c o n t a m i n a t -e d p h l o e m e x o d a t e s a m p l e s f r o m g r a p e v i n e s h a v e b e e nunsuccess fu l .

W o r k i s i n p r o g r e s s t o d e t e r m i n e t h e i m p o r t a n c e o fw i n d m o v e m e n t a n d l i g h t l e v e l s o n p h o t o s y n t h e s i s , s t o -m a t a l c o n d u c t a n c e a n d p o t a s s i u m a c c u m u l a t i o n i n f r u i t so f g rapev ines .

L I T E R A T U R E C I T E D1. Dtiring, H. Stud ies on env ironmen tally controlled stomataltranspiration in grapevines. I. Effec ts of light intensity and airhumidity. Vitis 15:82-7 (1976).2. H all, A. E. and E . D. Sch ulze. Stom atal respo nse to environ-ment and a possible interrelation between stomatal effects on tran-spiration and CO2 assimilation. Plant, Cell and Env ironme nt 3:467-74 (1980).3. HoF~icker, W. Inv estigations o n the influence of changing so ilwater sup ply on the photosynthesis intensity and the diffusiveresistance of vine leaves. Vitis 15:171-82 (1976).



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4 . K r i e d e m a n n , P . E . a n d R . E . S m a r t . E f f e c ts o f i r r a d i a n c e ,t e m p e r a t u r e a n d l e a f w a t e r p o t e n t i a l o n p h o t o s y n t h e s i s o f v in el e a v e s . Ph o t o sy n t h e t i c a 5 : 6 -1 5 (1 9 7 1 ) .5 . R a s c h k e , K . S t o m a t a l a c t i o n . A n n . R e v . P l a n t P h y s i o l . 2 6 :3 0 9 -40 (1975).6 . S m a r t , R . E . A s p e c t s o f w a t e r r e l a t i o n s o f t h e g r a p e v i n e ( V i t i s

v i n i f e r a ) . Am. J . En o l . Vi t i c . 2 5 : 8 4 -9 1 (1 9 7 4 ) .7 . S m i t h , J . A . C . a n d J . A . M i l b u r n . O s m o r e g u l a t i o n a n d t h ec o n t r o l o f p h l o e m - s a p c o m p o s i t i o n i n R i c i n u s c o m m u n i s L . P l a n t a148:28-34 (1980).8 . W a r r i t , B . , J . J . L a n d s b e r g a n d M . R . T h o r p e . R e s p o n s e s o fa p p l e l e af s t o m a t a t o e n v i r o n m e n t a l f a c t o r s . P l a n t , C e l l a n d E n v i r o n -me n t 3 : 1 3 -2 2 (1 9 8 0 ) .


Wind Breaks

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