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Growth responses of some greenhouse plants to environment. III. Design and function of a growth chamber prototype
Scientia Horticulturae, 16 (1982) 57--63 Elsevier Scientific Publishing Company, Amsterdam - - Printed in The Netherlands
57
GROWTH RESPONSES OF SOME GREENHOUSE PLANTS TO ENVIRONMENT. III. DESIGN AND FUNCTION OF A GROWTH CHAMBER PROTOTYPE
L.M. MORTENSEN Department of Floriculture and Greenhouse Crops, Agricultural University o f Norway, P.O. Box 13, N-1432 Aas-NLH (Norway) Report No. 248 (Accepted for publication 19 April 1981)
ABSTRACT
Mortensen, L.M., 1982. Growth responses of some greenhouse plants to environment. III. Design and function of a growth chamber prototype. Scientia Hortic., 16: 57--63. Growth chambers for the study of effects of temperature, air humidity and CO~concentration on plant growth, with or without supplementary artificial light, are described. Each chamber has a volume of 1080 1. The mean airflow at plant level is 0.22 m s-1. The temperature is controlled within -+ 0.5°C in the range from 10°C lower to 20°C higher than the ambient temperature at low solar radiation. In direct sunshine, the temperature may rise 1 ° C at floor level and the gradient from the floor to the upper part of the chamber may be about 2 ° C. The relative humidity is generally controlled within -+ 4%, in the range from 50 to 95%. The CO2-concentrationis controlled within + 5% of the desired value. The number of air changesin the chambers may be controlled from 0 to 20 h - i . Tests revealed no significant difference between the chambers with respect to fresh weight production of lettuce, rose or chrysanthemum. There was, however, a significant effect from the position within the chambers.
INTRODUCTION Growth chambers are useful in the study of the effect of environmental factors on plant growth and development. Such chambers may range from very simple boxes up to sophisticated systems with precise control of t e m p e r a t u r e , a i r h u m i d i t y , a i r f l o w , r a d i a t i o n a n d gas c o m p o s i t i o n ( H o f f m a n a n d R a w l i n s , 1 9 7 0 ; H a n d , 1 9 7 3 ; A c o c k , 1 9 7 4 ; A c o c k e t al., 1977). The complexity of the growth chamber depends on the nature of the experiments. Most growth chambers have air-flow rates from 0.05 to 0.3 m s-l, and the flow rate should not exceed 0.5 m s-1 (Acock, 1974). On the other hand, 0304,4238/82/0000--0000/$02.75 © 1982 Elsevier Scientific Publishing Company
58 in o r d e r t o o b t a i n precise t e m p e r a t u r e c o n t r o l at high radiation, as m a y be t h e case in d a y l i t c h a m b e r s , the air-flow s h o u l d n o t be t o o low. The air h u m i d i t y is o f t e n a s s u m e d t o have little or n o e f f e c t o n p l a n t g r o w t h , and is thus o f t e n n e g l e c t e d as a g r o w t h p a r a m e t e r . H o w e v e r , effects o f h u m i d i t y o n p l a n t g r o w t h have b e e n r e p o r t e d ( T h o r n e et al., 1 9 6 4 ; T h o r n e a n d F o r d , 1 9 6 5 , 1 9 6 6 , 1 9 6 9 ; Sale, 1 9 7 0 ; O ' L e a r y a n d K n e c h t , 1 9 7 1 ; Tibbits a n d B o t t e n b e r g , 1 9 7 6 ) . It is t h u s also o f i m p o r t a n c e t o c o n t r o l t h e air h u m i d i t y . Beneficial effects o f c a r b o n d i o x i d e (CO2) o n p l a n t g r o w t h have b e e n r e p o r t e d f o r several g r e e n h o u s e plants (Wittwer and R o b b , 1 9 6 4 ; Mfinch a n d Leinfelder, 1 9 6 8 ; Walla a n d Kristoffersen, 1 9 7 4 ; H a n d a n d Cockshull, 1 9 7 5 ; Moe, 1 9 7 7 ) . M u c h is y e t t o be learnt, h o w e v e r , a b o u t the e f f e c t o f CO2 o n o r n a m e n t a l plants at d i f f e r e n t light c o n d i t i o n s a n d air t e m p e r a t u r e s . This p a p e r describes d a y l i t g r o w t h c h a m b e r s w h i c h have been built in o r d e r t o s t u d y the e f f e c t o f CO2 f r o m b u r n i n g charcoal. In this case, p a r t o f t h e p r o b l e m has b e e n t o s t u d y t o w h a t e x t e n t plants m a y t o l e r a t e o t h e r gases p r o d u c e d in t h e b u r n i n g process. CHAMBER DESIGN AND CONTROL DEVICES T h e g r o w t h c h a m b e r is m a d e o f plexiglass a n d has a v o l u m e o f 1 0 8 0 1 (Fig. 1). It is n o m i n a l l y 6 9 0 m m wide, 1 2 8 5 m m long, a n d 1 2 2 0 m m high.
A o <~.
[
L
[
! !
! l
T ~ Tc
i "
F
Ct
~Tc J
sE
Pa
'
~FI
|
~Fw Wp
< -- . ~ - .
Water Airflflooww
Fig. 1. Growth chamber with control devices. Ai = air inlet; Ao = air outlet; C = coil for cooling; Ca = catalyst; Cm = cooling machine; Ct = contact thermometer; D = deionizer; F and Fc = fans; Fa = air filter; F1 = flowmeter; Fw = water filter; G = flap valve; H = electric heater; Hs = humidostat; Hy = hygrometer; Irga = infrared gas analyzer; J = nozzle; M = manometer; Ov = oven; Pa = air pump; Pw = water pump; Rec 1 and Rec 2 = recorders; S = solenoid valve; Si = Silica-gel; Tc = thermocouple; V = valve; W = water bath.
59 T h e air is c i r c u l a t e d b y 2 fans t h r o u g h a c h a n n e l a n d a p e r f o r a t e d polye t h y l e n e s h e e t o n which t h e p l a n t s are placed. T h e s h e e t is p e r f o r a t e d w i t h 1 0 - m m h o l e s w h i c h m a k e u p a b o u t 5% o f t h e t o t a l f l o o r a r e a ( 0 . 8 0 m f ) . T h e a i r - f l o w is m e a s u r e d 4 5 c m a b o v e t h e p l a n t f l o o r at 15 d i f f e r e n t positions. T h e f l o w ranges f r o m a b o u t 0 . 1 5 m s-1 close to t h e walls t o a b o u t 0 . 3 5 m s-1 in t h e c e n t e r o f t h e c h a m b e r . W h e n 30 p o t s ( 1 1 0 m m d i a m e t e r ) w e r e p l a c e d o n t h e f l o o r , t h e air f l o w was m o r e e v e n l y d i s t r i b u t e d . T h e m e a n air-flow m e a s u r e d was 0 . 2 2 m s - 1 . T h e air-flow is t u r b u l e n t a n d t h u s d i f f i c u l t t o m e a s u r e . W h e n p o t s w e r e p l a c e d in t h e c h a m b e r , t h e f l o w was higher b e t w e e n a n d j u s t a b o v e t h e p o t s and d e p e n d e d o n t h e size a n d n u m b e r o f pots. T h e air f l o w p a t t e r n was o b s e r v e d b y m e a n s o f s m o k e f r o m a s m o k e - c a r t r i d g e . T h e air a s c e n d s t o t h e t o p o f t h e c h a m b e r a n d is t h e n d r a w n t o w a r d s t h e fans. T h e air in t h e c h a m b e r is c i r c u l a t e d t h r o u g h t h e c h a n n e l w i t h i n 6 s. T h e t e m p e r a t u r e is c o n t r o l l e d b y a c o n t a c t t h e r m o m e t e r w h i c h o p e r a t e s a 7 0 0 - w a t t electric h e a t e r p l a c e d in t h e channel. T h e t e m p e r a t u r e is usually m e a s u r e d at p o t level a n d at a level o f 75 c m a b o v e t h e f l o o r b y m e a n s o f t h e r m o c o u p l e s . In o r d e r t o o b t a i n precise c o n t r o l at high a m b i e n t t e m p e r a t u r e s a n d in sunshine, c o l d w a t e r is c o n t i n u o u s l y c i r c u l a t e d t h r o u g h a c o p p e r coil w h i c h is p l a c e d b e l o w t h e h e a t e r in t h e channel. T h e t e m p e r a t u r e o f t h e w a t e r is c o n t r o l l e d b y a t h e r m o s t a t w h i c h o p e r a t e s a c o o l i n g - m a c h i n e ( 7 3 5 w a t t ) . T h e w a t e r f l o w is c o n t r o l l e d b y an a d j u s t a b l e p u m p . T h e air t e m p e r a t u r e is c o n t r o l l e d w i t h i n - 0.5 C. I n s u n s h i n e in S e p t e m b e r , h o w ever, t h e t e m p e r a t u r e m a y rise 0 . 5 ~ 1 ° C a t f l o o r level a n d 2 - - 3 ° C 75 c m a b o v e t h e p l a n t floor. W h e n t h e a m b m n t t e m p e r a t u r e is 18 C, a m l m m u m t e m p e r a t u e o f 8 C a n d a m a x i m u m t e m p e r a t u r e o f 40 C m a y b e o b t a i n e d in the c h a m b e r s . T h e t e m p e r a t u r e was m e a s u r e d w h e n t h e n u m b e r o f air c h a n g e s in t h e c h a m b e r was 1 5 h - 1 . T h e h u m i d i t y is c o n t r o l l e d b y m e a n s o f a h y g r o s t a t w h i c h o p e r a t e s a s o l e n o i d valve w h i c h again c o n t r o l s a n o z z l e p l a c e d in t h e channel. W h e n w a t e r is s u p p l i e d t o t h e n o z z l e a t a r a t e o f a b o u t 1.5 1 h - 1 , t h e air h u m i d i t y increases r a p i d l y . T h e h u m i d i t y is l o w e r e d b y t h e c o l d - w a t e r coil o n w h i c h w a t e r v a p o u r c o n d e n s e s , a n d b y f r e s h air e n t e r i n g t h e c h a m b e r in cases w h e n this air has a l o w e r h u m i d i t y . T h e r a n g e o f h u m i d i t y c o n t r o l d e p e n d s m a i n l y o n t h e a m o u n t o f p l a n t m a s s in t h e c h a m b e r a n d o n air t e m p e r a t u r e , b u t coil t e m p e r a t u r e a n d t h e n u m b e r o f air c h a n g e s are also o f i m p o r t a n c e . G e n e r a l l y , t h e relative h u m i d i t y ( R H ) m a y be c o n t r o l l e d w i t h i n + 4% in t h e r a n g e f r o m 50 to 95%. W h e n t h e r e is m u c h p l a n t m a t e r i a l in t h e c h a m b e r , it is d i f f i c u l t t o o b t a i n R H l o w e r t h a n 65%. T h e CO2 c o n c e n t r a t i o n is c o n t r o l l e d b y m i x i n g fresh air w i t h t h e c o m b u s t i o n gases f r o m an o v e n m a d e for b u r n i n g c h a r c o a l . A f a n ( 0 - - 1 2 V) b l o w s air i n t o t h e o v e n a n d t h e c o m b u s t i o n gas passes t h r o u g h a c a t a l y s t a n d an 1 8 - m m plastic t u b e u n t i l it is m i x e d w i t h f r e s h air s u p p l i e d b y a n o t h e r fan. T h e c o m b u s t i o n gas c o n t a i n s a b o u t 16% CO2. P o l l u t i n g gases s u c h as e t h y l e n e a n d c a r b o n m o n o x i d e are e f f i c i e n t l y r e m o v e d b y a c a t a l y s t a t a •
r
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60 temperature of 450°C (Soma, 1980; Mortensen, 1981). The number of air changes in the chamber are controlled by flap valves. The air flow to the chamber is measured by a calibrated manometer. The CO2 concentration is controlled within + 5% of the desired value. The CO2 concentration in the chamber is measured at intervals of 5 min by an infrared gas analyzer (Infralyt-T, VEB Junkalor, Dessau D D R ) . An airswitch makes it possible to analyze 6 different air streams in sequence. The water vapour is removed by silica-gel and the air is cleaned with a filter before it enters the analyzer. The flow rate is 50 1 h - ' . Nine identical growth chambers were made and placed in a greenhouse compartment. Three cooling-machines supply cold water, each serving 3 chambers. During the winter season, supplementary light is given as shown in Fig. 2.
Fig. 2. Picture of the growth chambers. AIR POLLUTION IN PLEXIGLASS CHAMBERS
Young t o m a t o and cucumber plants (cultivars 'Virosa' and 'Farbio') failed to grow in the chambers. Within 2 days the plants were severely damaged, and within 1 week t h e y died. Experiments indicated that the plexiglass walls of the chambers develop harmful gases when sprayed with water containing calcium. This problem will be dealt with in a following paper. Roses, lettuce and chrysanthemums, however, were n o t affected.
61 EFFECT OF CHAMBER AND POSITION WITHIN CHAMBER ON PLANT GROWTH Five p l a n t s o f roses ( ' M e r c e d e s ' a n d ' G a r n e t t e ' ) a n d o f l e t t u c e ( ' O s t i n a t a ' ) w e r e p l a c e d in e a c h c h a m b e r . T h e r o s e p l a n t s w e r e p r o p a g a t e d b y c u t t i n g s a n d w e r e p i n c h e d a b o v e 5 leaves at t h e s t a r t o f t h e e x p e r i m e n t . T h e n e w shoots were harvested after 6 weeks. The lettuce plants were harvested 4 w e e k s a f t e r t h e s t a r t o f t h e e x p e r i m e n t . T h e air t e m p e r a t u r e was 1 8 . 0 + 0.5°C, a n d t h e relative h u m i d i t y 75 + 4%. T h e CO2 c o n c e n t r a t i o n was 0 . 0 3 % a n d t h e n u m b e r o f air c h a n g e s 15 h - 1 . Statistical v a r i a n c e a n a l y s i s was p e r f o r m e d b y a c o m p u t e r p r o g r a m f o r f a c t o r i a l e x p e r i m e n t s . T a b l e I s h o w s t h e m e a n f r e s h w e i g h t o f t h e p l a n t s in e a c h c h a m b e r . N o significant d i f f e r e n c e (ns) b e t w e e n c h a m b e r s was f o u n d w i t h r e s p e c t t o fresh w e i g h t of the plant material. TABLE I The mean fresh weight (g) of L a e t u c a 'Ostinata', R o s a 'Mercedes' and R o s a 'Garnette' grown in the 9 chambers Chamber
'Ostinata'
'Mercedes'
'Garnette'
~-
1 2 3 4 5 6 7 8 9
67.0 75.4 77.5 72.4 67.8 71.4 68.3 69.7 71.6
20.4 22.6 16.6 20.7 19.2 18.7 21.5 19.2 17.5
14.2 13.5 13.0 15.3 12.4 13.3 14.5 14.6 13.6
33.8 37.1 35.7 36.1 33.2 34.5 34.6 34.5 34.3
Significances of main effect and interaction at P = 0.05: chamber, ns; chamber X cultivar, as.
The effect of the position within the chambers on growth of chrysant h e m u m ' Y e l l o w M a n d a l a y ' was i n v e s t i g a t e d in a similar e x p e r i m e n t . T h r e e g r o u p s o f 5 r o o t e d c u t t i n g s w e r e p l a c e d a t d i f f e r e n t p o s i t i o n s in t h e c h a m b e r a n d g r o w n f o r 6 w e e k s . T h e first g r o u p was p l a c e d close t o t h e c h a n n e l ( P o s i t i o n 1), t h e s e c o n d in t h e m i d d l e o f t h e c h a m b e r ( P o s i t i o n 2) a n d t h e t h i r d a t t h e o p p o s i t e e n d t o t h e c h a n n e l ( P o s i t i o n 3). T a b l e I I s h o w s t h e m e a n f r e s h w e i g h t s o f t h e plants. Analysis o f v a r i a n c e s h o w e d a significant e f f e c t o f p o s i t i o n o n fresh w e i g h t (P < 0.01). Again, n o e f f e c t o f t h e c h a m b e r s o n t h e fresh w e i g h t was o b s e r v e d . T h e results o f this t e s t s h o w t h a t it is i m p o r t a n t t o use p l a n t s p l a c e d at i d e n t i c a l p o s i t i o n s in t h e c h a m b e r s w h e n s t u d y i n g t h e e f f e c t s o f t r e a t m e n t s . T h e l o w e s t fresh w e i g h t s w e r e o b s e r v e d in P o s i t i o n 1. This m a y b e d u e t o less light in this p o s i t i o n b e c a u s e o f t h e m e t a l screens l o c a t e d in t h e c h a n n e l . T h e c o m p a r i s o n b e t w e e n t h e c h a m b e r s was d o n e in A u g u s t - -
62 TABLEII The mean ~esh weight(g) of Ch~san~emum 'Yellow Mandalay'grown a t 3 positionsin each chamber Position
1 2 3
Chamber 1
2
3
4
5
6
7
8
9
47.6 49.7 50.6
48.6 56.3 46.7
42.5 49.1 44.6
50.8 51.6 52.6
47.5 52.4 54.5
49.5 50.6 54.8
45.8 55.7 55.9
50.3 54.6 64.2
45.9 47.0 62.7
47.6 51.9 54.0
Significance of main effects and interaction: chamber, ns; position, significant at P < 0.01 ; chamber × position, ns.
September. The light distribution in the greenhouse may change during the year in such a way that some chambers receive more light than others, This should be recorded. In order to determine the radiation in the chambers during the experimental periods, light integrators with a radiometric sensor ( U D T 2 2 3 r a d i o m e t r i c s e n s o r , 4 0 0 - - 1 0 0 0 n m ) will b e u s e d i n f u t u r e e x p e r i ments. ACKNOWLEDGEMENTS I a m g r a t e f u l t o Dr. R. M o e a n d P r o f . E. Str~bmme f o r v a l u a b l e d i s c u s s i o n during the work and for reading the manuscript. The technical assistance of Mr. A. H a m r e a n d Mr. M. S o m a is a c k n o w l e d g e d . T h e w o r k w a s s u p p o r t e d by a grant from the National Agricultural Research Council and the Royal Ministry of Petroleum and Energy of Norway.
REFERENCES Acock, B., 1974. The design and use of growth chambers for investigating the effects of environmental factors on plant growth. Acta Hortic., 39: 15--37. Acock, B., Charles-Edwards, D.A. and Hearn, A.R., 1977. Growth response of a chrysanthemum crop to the environment. I. Experimental techniques. Ann. Bot., 41: 41--48. Hand, D.W., 1973. A null-balance method for measuring crop photosynthesis in an airtight daylit controlled-environment cabinet. Agric. Meteorol., 12: 259--270. Hand, D.W. and Cockshull, K.E., 1975. Roses I: The effects of CO 2 enrichment on winter bloom production. J. Hortic. Sci., 50: 183--192. Hoffmann, G.J. and Rawlins, S.L., 1970. Design and performance of sunlit climate chambers. Trans. ASAE, 13: 656--660. Moe, R., 1977. Effect of light, temperature and CO~ on the growth of Campanula isophylla stock plants and the subsequent growth and development of their cuttings. Scientia Hortic., 6 : 129--141. Mortensen, L.M., 1981. Charcoal as a carbon dioxide source in greenhouses. Gartenbauwissenschaft, in press.
63 Mtlnch and Leinfelder, 1968. Wirkung zus~tzlicher Begasung mit CO2 auf Aphelandra squarrosa 'Typ Koniger'. Gartenwelt, 68 (11): 239--241. O'Leary, J.W. and Knecht, G.N., 1971. The effect of relative humidity on growth, yield, and water consumption of bean plants. J. Am. Soc. Hortic. Sci., 96: 263--265. Sale, P.J.M., 1970. Growth and flowering of cacao under controlled atmospheric relative humidities. J. Hortic. Sci., 45: 119--132. Soma, M.H., 1980. Trekullbasert CO2 -generator for brok i velesthus. (Charcoal based generation of CO: for greenhouses.) Norwegian Defence Research Establishment, Tech. Rep. No. VM-4041. Thorne, G.N. and Ford, M.A., 1965. Effect of humidity and temperature on growth. Rep. Rothamsted Exp. Stn. 1964: 105--106. Thorne, G.N. and Ford, M.A., 1966. Effects of atmospheric humidity on growth. Rep. Rothamsted Exp. Stn. 1965: 98--99. Thorne, G.N. and Ford, M.A., 1969. Effects of atmospheric humidity on growth. Rep. Rothamsted Exp. Stn. 1968: 94--95. Thorne, G.N., Orchard, B and Ford, M.A., 1964. Effects of humidity on growth. Rep. Rothamsted Exp. Stn. 1963: 78--79. Tibbits, TiW. and Bottenberg, G., 1976. Growth of lettuce under controlled humidity levels. J. Am. Soc. Hortic. Sci., 101: 70--73. Walla, I. and Kristoffersen, T., 1974. Virkning av CO~-tilhbrsel under ulike lys -- og temperaturforhold p~ vekst og utvikling hos noen blomsterkulterer. Meld. Nor. Landbrukshoegsk., 53 (27): 1--46. Wittwer, S.H. and Robb, W.M., 1964. Carbon dioxide enrichment of greenhouse atmospheres for food crop production. Econ. Bot., 18: 34--56.
57
GROWTH RESPONSES OF SOME GREENHOUSE PLANTS TO ENVIRONMENT. III. DESIGN AND FUNCTION OF A GROWTH CHAMBER PROTOTYPE
L.M. MORTENSEN Department of Floriculture and Greenhouse Crops, Agricultural University o f Norway, P.O. Box 13, N-1432 Aas-NLH (Norway) Report No. 248 (Accepted for publication 19 April 1981)
ABSTRACT
Mortensen, L.M., 1982. Growth responses of some greenhouse plants to environment. III. Design and function of a growth chamber prototype. Scientia Hortic., 16: 57--63. Growth chambers for the study of effects of temperature, air humidity and CO~concentration on plant growth, with or without supplementary artificial light, are described. Each chamber has a volume of 1080 1. The mean airflow at plant level is 0.22 m s-1. The temperature is controlled within -+ 0.5°C in the range from 10°C lower to 20°C higher than the ambient temperature at low solar radiation. In direct sunshine, the temperature may rise 1 ° C at floor level and the gradient from the floor to the upper part of the chamber may be about 2 ° C. The relative humidity is generally controlled within -+ 4%, in the range from 50 to 95%. The CO2-concentrationis controlled within + 5% of the desired value. The number of air changesin the chambers may be controlled from 0 to 20 h - i . Tests revealed no significant difference between the chambers with respect to fresh weight production of lettuce, rose or chrysanthemum. There was, however, a significant effect from the position within the chambers.
INTRODUCTION Growth chambers are useful in the study of the effect of environmental factors on plant growth and development. Such chambers may range from very simple boxes up to sophisticated systems with precise control of t e m p e r a t u r e , a i r h u m i d i t y , a i r f l o w , r a d i a t i o n a n d gas c o m p o s i t i o n ( H o f f m a n a n d R a w l i n s , 1 9 7 0 ; H a n d , 1 9 7 3 ; A c o c k , 1 9 7 4 ; A c o c k e t al., 1977). The complexity of the growth chamber depends on the nature of the experiments. Most growth chambers have air-flow rates from 0.05 to 0.3 m s-l, and the flow rate should not exceed 0.5 m s-1 (Acock, 1974). On the other hand, 0304,4238/82/0000--0000/$02.75 © 1982 Elsevier Scientific Publishing Company
58 in o r d e r t o o b t a i n precise t e m p e r a t u r e c o n t r o l at high radiation, as m a y be t h e case in d a y l i t c h a m b e r s , the air-flow s h o u l d n o t be t o o low. The air h u m i d i t y is o f t e n a s s u m e d t o have little or n o e f f e c t o n p l a n t g r o w t h , and is thus o f t e n n e g l e c t e d as a g r o w t h p a r a m e t e r . H o w e v e r , effects o f h u m i d i t y o n p l a n t g r o w t h have b e e n r e p o r t e d ( T h o r n e et al., 1 9 6 4 ; T h o r n e a n d F o r d , 1 9 6 5 , 1 9 6 6 , 1 9 6 9 ; Sale, 1 9 7 0 ; O ' L e a r y a n d K n e c h t , 1 9 7 1 ; Tibbits a n d B o t t e n b e r g , 1 9 7 6 ) . It is t h u s also o f i m p o r t a n c e t o c o n t r o l t h e air h u m i d i t y . Beneficial effects o f c a r b o n d i o x i d e (CO2) o n p l a n t g r o w t h have b e e n r e p o r t e d f o r several g r e e n h o u s e plants (Wittwer and R o b b , 1 9 6 4 ; Mfinch a n d Leinfelder, 1 9 6 8 ; Walla a n d Kristoffersen, 1 9 7 4 ; H a n d a n d Cockshull, 1 9 7 5 ; Moe, 1 9 7 7 ) . M u c h is y e t t o be learnt, h o w e v e r , a b o u t the e f f e c t o f CO2 o n o r n a m e n t a l plants at d i f f e r e n t light c o n d i t i o n s a n d air t e m p e r a t u r e s . This p a p e r describes d a y l i t g r o w t h c h a m b e r s w h i c h have been built in o r d e r t o s t u d y the e f f e c t o f CO2 f r o m b u r n i n g charcoal. In this case, p a r t o f t h e p r o b l e m has b e e n t o s t u d y t o w h a t e x t e n t plants m a y t o l e r a t e o t h e r gases p r o d u c e d in t h e b u r n i n g process. CHAMBER DESIGN AND CONTROL DEVICES T h e g r o w t h c h a m b e r is m a d e o f plexiglass a n d has a v o l u m e o f 1 0 8 0 1 (Fig. 1). It is n o m i n a l l y 6 9 0 m m wide, 1 2 8 5 m m long, a n d 1 2 2 0 m m high.
A o <~.
[
L
[
! !
! l
T ~ Tc
i "
F
Ct
~Tc J
sE
Pa
'
~FI
|
~Fw Wp
< -- . ~ - .
Water Airflflooww
Fig. 1. Growth chamber with control devices. Ai = air inlet; Ao = air outlet; C = coil for cooling; Ca = catalyst; Cm = cooling machine; Ct = contact thermometer; D = deionizer; F and Fc = fans; Fa = air filter; F1 = flowmeter; Fw = water filter; G = flap valve; H = electric heater; Hs = humidostat; Hy = hygrometer; Irga = infrared gas analyzer; J = nozzle; M = manometer; Ov = oven; Pa = air pump; Pw = water pump; Rec 1 and Rec 2 = recorders; S = solenoid valve; Si = Silica-gel; Tc = thermocouple; V = valve; W = water bath.
59 T h e air is c i r c u l a t e d b y 2 fans t h r o u g h a c h a n n e l a n d a p e r f o r a t e d polye t h y l e n e s h e e t o n which t h e p l a n t s are placed. T h e s h e e t is p e r f o r a t e d w i t h 1 0 - m m h o l e s w h i c h m a k e u p a b o u t 5% o f t h e t o t a l f l o o r a r e a ( 0 . 8 0 m f ) . T h e a i r - f l o w is m e a s u r e d 4 5 c m a b o v e t h e p l a n t f l o o r at 15 d i f f e r e n t positions. T h e f l o w ranges f r o m a b o u t 0 . 1 5 m s-1 close to t h e walls t o a b o u t 0 . 3 5 m s-1 in t h e c e n t e r o f t h e c h a m b e r . W h e n 30 p o t s ( 1 1 0 m m d i a m e t e r ) w e r e p l a c e d o n t h e f l o o r , t h e air f l o w was m o r e e v e n l y d i s t r i b u t e d . T h e m e a n air-flow m e a s u r e d was 0 . 2 2 m s - 1 . T h e air-flow is t u r b u l e n t a n d t h u s d i f f i c u l t t o m e a s u r e . W h e n p o t s w e r e p l a c e d in t h e c h a m b e r , t h e f l o w was higher b e t w e e n a n d j u s t a b o v e t h e p o t s and d e p e n d e d o n t h e size a n d n u m b e r o f pots. T h e air f l o w p a t t e r n was o b s e r v e d b y m e a n s o f s m o k e f r o m a s m o k e - c a r t r i d g e . T h e air a s c e n d s t o t h e t o p o f t h e c h a m b e r a n d is t h e n d r a w n t o w a r d s t h e fans. T h e air in t h e c h a m b e r is c i r c u l a t e d t h r o u g h t h e c h a n n e l w i t h i n 6 s. T h e t e m p e r a t u r e is c o n t r o l l e d b y a c o n t a c t t h e r m o m e t e r w h i c h o p e r a t e s a 7 0 0 - w a t t electric h e a t e r p l a c e d in t h e channel. T h e t e m p e r a t u r e is usually m e a s u r e d at p o t level a n d at a level o f 75 c m a b o v e t h e f l o o r b y m e a n s o f t h e r m o c o u p l e s . In o r d e r t o o b t a i n precise c o n t r o l at high a m b i e n t t e m p e r a t u r e s a n d in sunshine, c o l d w a t e r is c o n t i n u o u s l y c i r c u l a t e d t h r o u g h a c o p p e r coil w h i c h is p l a c e d b e l o w t h e h e a t e r in t h e channel. T h e t e m p e r a t u r e o f t h e w a t e r is c o n t r o l l e d b y a t h e r m o s t a t w h i c h o p e r a t e s a c o o l i n g - m a c h i n e ( 7 3 5 w a t t ) . T h e w a t e r f l o w is c o n t r o l l e d b y an a d j u s t a b l e p u m p . T h e air t e m p e r a t u r e is c o n t r o l l e d w i t h i n - 0.5 C. I n s u n s h i n e in S e p t e m b e r , h o w ever, t h e t e m p e r a t u r e m a y rise 0 . 5 ~ 1 ° C a t f l o o r level a n d 2 - - 3 ° C 75 c m a b o v e t h e p l a n t floor. W h e n t h e a m b m n t t e m p e r a t u r e is 18 C, a m l m m u m t e m p e r a t u e o f 8 C a n d a m a x i m u m t e m p e r a t u r e o f 40 C m a y b e o b t a i n e d in the c h a m b e r s . T h e t e m p e r a t u r e was m e a s u r e d w h e n t h e n u m b e r o f air c h a n g e s in t h e c h a m b e r was 1 5 h - 1 . T h e h u m i d i t y is c o n t r o l l e d b y m e a n s o f a h y g r o s t a t w h i c h o p e r a t e s a s o l e n o i d valve w h i c h again c o n t r o l s a n o z z l e p l a c e d in t h e channel. W h e n w a t e r is s u p p l i e d t o t h e n o z z l e a t a r a t e o f a b o u t 1.5 1 h - 1 , t h e air h u m i d i t y increases r a p i d l y . T h e h u m i d i t y is l o w e r e d b y t h e c o l d - w a t e r coil o n w h i c h w a t e r v a p o u r c o n d e n s e s , a n d b y f r e s h air e n t e r i n g t h e c h a m b e r in cases w h e n this air has a l o w e r h u m i d i t y . T h e r a n g e o f h u m i d i t y c o n t r o l d e p e n d s m a i n l y o n t h e a m o u n t o f p l a n t m a s s in t h e c h a m b e r a n d o n air t e m p e r a t u r e , b u t coil t e m p e r a t u r e a n d t h e n u m b e r o f air c h a n g e s are also o f i m p o r t a n c e . G e n e r a l l y , t h e relative h u m i d i t y ( R H ) m a y be c o n t r o l l e d w i t h i n + 4% in t h e r a n g e f r o m 50 to 95%. W h e n t h e r e is m u c h p l a n t m a t e r i a l in t h e c h a m b e r , it is d i f f i c u l t t o o b t a i n R H l o w e r t h a n 65%. T h e CO2 c o n c e n t r a t i o n is c o n t r o l l e d b y m i x i n g fresh air w i t h t h e c o m b u s t i o n gases f r o m an o v e n m a d e for b u r n i n g c h a r c o a l . A f a n ( 0 - - 1 2 V) b l o w s air i n t o t h e o v e n a n d t h e c o m b u s t i o n gas passes t h r o u g h a c a t a l y s t a n d an 1 8 - m m plastic t u b e u n t i l it is m i x e d w i t h f r e s h air s u p p l i e d b y a n o t h e r fan. T h e c o m b u s t i o n gas c o n t a i n s a b o u t 16% CO2. P o l l u t i n g gases s u c h as e t h y l e n e a n d c a r b o n m o n o x i d e are e f f i c i e n t l y r e m o v e d b y a c a t a l y s t a t a •
r
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60 temperature of 450°C (Soma, 1980; Mortensen, 1981). The number of air changes in the chamber are controlled by flap valves. The air flow to the chamber is measured by a calibrated manometer. The CO2 concentration is controlled within + 5% of the desired value. The CO2 concentration in the chamber is measured at intervals of 5 min by an infrared gas analyzer (Infralyt-T, VEB Junkalor, Dessau D D R ) . An airswitch makes it possible to analyze 6 different air streams in sequence. The water vapour is removed by silica-gel and the air is cleaned with a filter before it enters the analyzer. The flow rate is 50 1 h - ' . Nine identical growth chambers were made and placed in a greenhouse compartment. Three cooling-machines supply cold water, each serving 3 chambers. During the winter season, supplementary light is given as shown in Fig. 2.
Fig. 2. Picture of the growth chambers. AIR POLLUTION IN PLEXIGLASS CHAMBERS
Young t o m a t o and cucumber plants (cultivars 'Virosa' and 'Farbio') failed to grow in the chambers. Within 2 days the plants were severely damaged, and within 1 week t h e y died. Experiments indicated that the plexiglass walls of the chambers develop harmful gases when sprayed with water containing calcium. This problem will be dealt with in a following paper. Roses, lettuce and chrysanthemums, however, were n o t affected.
61 EFFECT OF CHAMBER AND POSITION WITHIN CHAMBER ON PLANT GROWTH Five p l a n t s o f roses ( ' M e r c e d e s ' a n d ' G a r n e t t e ' ) a n d o f l e t t u c e ( ' O s t i n a t a ' ) w e r e p l a c e d in e a c h c h a m b e r . T h e r o s e p l a n t s w e r e p r o p a g a t e d b y c u t t i n g s a n d w e r e p i n c h e d a b o v e 5 leaves at t h e s t a r t o f t h e e x p e r i m e n t . T h e n e w shoots were harvested after 6 weeks. The lettuce plants were harvested 4 w e e k s a f t e r t h e s t a r t o f t h e e x p e r i m e n t . T h e air t e m p e r a t u r e was 1 8 . 0 + 0.5°C, a n d t h e relative h u m i d i t y 75 + 4%. T h e CO2 c o n c e n t r a t i o n was 0 . 0 3 % a n d t h e n u m b e r o f air c h a n g e s 15 h - 1 . Statistical v a r i a n c e a n a l y s i s was p e r f o r m e d b y a c o m p u t e r p r o g r a m f o r f a c t o r i a l e x p e r i m e n t s . T a b l e I s h o w s t h e m e a n f r e s h w e i g h t o f t h e p l a n t s in e a c h c h a m b e r . N o significant d i f f e r e n c e (ns) b e t w e e n c h a m b e r s was f o u n d w i t h r e s p e c t t o fresh w e i g h t of the plant material. TABLE I The mean fresh weight (g) of L a e t u c a 'Ostinata', R o s a 'Mercedes' and R o s a 'Garnette' grown in the 9 chambers Chamber
'Ostinata'
'Mercedes'
'Garnette'
~-
1 2 3 4 5 6 7 8 9
67.0 75.4 77.5 72.4 67.8 71.4 68.3 69.7 71.6
20.4 22.6 16.6 20.7 19.2 18.7 21.5 19.2 17.5
14.2 13.5 13.0 15.3 12.4 13.3 14.5 14.6 13.6
33.8 37.1 35.7 36.1 33.2 34.5 34.6 34.5 34.3
Significances of main effect and interaction at P = 0.05: chamber, ns; chamber X cultivar, as.
The effect of the position within the chambers on growth of chrysant h e m u m ' Y e l l o w M a n d a l a y ' was i n v e s t i g a t e d in a similar e x p e r i m e n t . T h r e e g r o u p s o f 5 r o o t e d c u t t i n g s w e r e p l a c e d a t d i f f e r e n t p o s i t i o n s in t h e c h a m b e r a n d g r o w n f o r 6 w e e k s . T h e first g r o u p was p l a c e d close t o t h e c h a n n e l ( P o s i t i o n 1), t h e s e c o n d in t h e m i d d l e o f t h e c h a m b e r ( P o s i t i o n 2) a n d t h e t h i r d a t t h e o p p o s i t e e n d t o t h e c h a n n e l ( P o s i t i o n 3). T a b l e I I s h o w s t h e m e a n f r e s h w e i g h t s o f t h e plants. Analysis o f v a r i a n c e s h o w e d a significant e f f e c t o f p o s i t i o n o n fresh w e i g h t (P < 0.01). Again, n o e f f e c t o f t h e c h a m b e r s o n t h e fresh w e i g h t was o b s e r v e d . T h e results o f this t e s t s h o w t h a t it is i m p o r t a n t t o use p l a n t s p l a c e d at i d e n t i c a l p o s i t i o n s in t h e c h a m b e r s w h e n s t u d y i n g t h e e f f e c t s o f t r e a t m e n t s . T h e l o w e s t fresh w e i g h t s w e r e o b s e r v e d in P o s i t i o n 1. This m a y b e d u e t o less light in this p o s i t i o n b e c a u s e o f t h e m e t a l screens l o c a t e d in t h e c h a n n e l . T h e c o m p a r i s o n b e t w e e n t h e c h a m b e r s was d o n e in A u g u s t - -
62 TABLEII The mean ~esh weight(g) of Ch~san~emum 'Yellow Mandalay'grown a t 3 positionsin each chamber Position
1 2 3
Chamber 1
2
3
4
5
6
7
8
9
47.6 49.7 50.6
48.6 56.3 46.7
42.5 49.1 44.6
50.8 51.6 52.6
47.5 52.4 54.5
49.5 50.6 54.8
45.8 55.7 55.9
50.3 54.6 64.2
45.9 47.0 62.7
47.6 51.9 54.0
Significance of main effects and interaction: chamber, ns; position, significant at P < 0.01 ; chamber × position, ns.
September. The light distribution in the greenhouse may change during the year in such a way that some chambers receive more light than others, This should be recorded. In order to determine the radiation in the chambers during the experimental periods, light integrators with a radiometric sensor ( U D T 2 2 3 r a d i o m e t r i c s e n s o r , 4 0 0 - - 1 0 0 0 n m ) will b e u s e d i n f u t u r e e x p e r i ments. ACKNOWLEDGEMENTS I a m g r a t e f u l t o Dr. R. M o e a n d P r o f . E. Str~bmme f o r v a l u a b l e d i s c u s s i o n during the work and for reading the manuscript. The technical assistance of Mr. A. H a m r e a n d Mr. M. S o m a is a c k n o w l e d g e d . T h e w o r k w a s s u p p o r t e d by a grant from the National Agricultural Research Council and the Royal Ministry of Petroleum and Energy of Norway.
REFERENCES Acock, B., 1974. The design and use of growth chambers for investigating the effects of environmental factors on plant growth. Acta Hortic., 39: 15--37. Acock, B., Charles-Edwards, D.A. and Hearn, A.R., 1977. Growth response of a chrysanthemum crop to the environment. I. Experimental techniques. Ann. Bot., 41: 41--48. Hand, D.W., 1973. A null-balance method for measuring crop photosynthesis in an airtight daylit controlled-environment cabinet. Agric. Meteorol., 12: 259--270. Hand, D.W. and Cockshull, K.E., 1975. Roses I: The effects of CO 2 enrichment on winter bloom production. J. Hortic. Sci., 50: 183--192. Hoffmann, G.J. and Rawlins, S.L., 1970. Design and performance of sunlit climate chambers. Trans. ASAE, 13: 656--660. Moe, R., 1977. Effect of light, temperature and CO~ on the growth of Campanula isophylla stock plants and the subsequent growth and development of their cuttings. Scientia Hortic., 6 : 129--141. Mortensen, L.M., 1981. Charcoal as a carbon dioxide source in greenhouses. Gartenbauwissenschaft, in press.
63 Mtlnch and Leinfelder, 1968. Wirkung zus~tzlicher Begasung mit CO2 auf Aphelandra squarrosa 'Typ Koniger'. Gartenwelt, 68 (11): 239--241. O'Leary, J.W. and Knecht, G.N., 1971. The effect of relative humidity on growth, yield, and water consumption of bean plants. J. Am. Soc. Hortic. Sci., 96: 263--265. Sale, P.J.M., 1970. Growth and flowering of cacao under controlled atmospheric relative humidities. J. Hortic. Sci., 45: 119--132. Soma, M.H., 1980. Trekullbasert CO2 -generator for brok i velesthus. (Charcoal based generation of CO: for greenhouses.) Norwegian Defence Research Establishment, Tech. Rep. No. VM-4041. Thorne, G.N. and Ford, M.A., 1965. Effect of humidity and temperature on growth. Rep. Rothamsted Exp. Stn. 1964: 105--106. Thorne, G.N. and Ford, M.A., 1966. Effects of atmospheric humidity on growth. Rep. Rothamsted Exp. Stn. 1965: 98--99. Thorne, G.N. and Ford, M.A., 1969. Effects of atmospheric humidity on growth. Rep. Rothamsted Exp. Stn. 1968: 94--95. Thorne, G.N., Orchard, B and Ford, M.A., 1964. Effects of humidity on growth. Rep. Rothamsted Exp. Stn. 1963: 78--79. Tibbits, TiW. and Bottenberg, G., 1976. Growth of lettuce under controlled humidity levels. J. Am. Soc. Hortic. Sci., 101: 70--73. Walla, I. and Kristoffersen, T., 1974. Virkning av CO~-tilhbrsel under ulike lys -- og temperaturforhold p~ vekst og utvikling hos noen blomsterkulterer. Meld. Nor. Landbrukshoegsk., 53 (27): 1--46. Wittwer, S.H. and Robb, W.M., 1964. Carbon dioxide enrichment of greenhouse atmospheres for food crop production. Econ. Bot., 18: 34--56.