- Email: [email protected]
Acclimation Environment Control After Grafting - A New Acclimation Method -
4e-OI 2
Copyright@ 1996IFAC 131h Triennial World Congress. San Francisco. USA
ACCLIMA TlON ENVIRONMENT CONTROL AFfER GRAFTING - A NEW ACCLIMATlON METHOD-
Y.Nishiura, RMurase, N.Honanti
Lab, of Rioinstrumentation, Control and Systems Engineering Department of Regional Environmental Science. Faculty of Agricullur(~ UniversilyofO.,aka Prefeclure, I-I Gakuen-cho, Sakai, Osaka 593, JAPAN
Abstract: The production system for grafted seedlings consists of mainly three parts. Onc is the growing process, another one is the grafting process, and the last onc is the acc1imation process, The acc1imation process is very important for grafted seedlings because they arc seriously injured. The qualities of seedlings and the management of farmers and seedling producers depend upon the acclimating technologies. Now, we are trying to develop such a grafting robot system which satisfies the conditions in the view of plant histological and physiological standpoints. In this study we show a new acclimation method on the basis of high technologies. Keywords: Photosynthesis interval , Acclimation environment control. Wilting behavior. Machine vision technique. Bioinstrumentation. Wilting model. Grafting robot system, Bioproduction
I. INTRODUCTION
In general, it is necessary for acc1imating grafted seedlings to spend for about 70r 10 days under the conditions of 2528'C(air temp _) , 90%(R. H) , 12hours(light and dark interval period), 5klux (light intensity : tomato: light saturation point 70klux), 3klux (light intensity: eggplant, watermelon; light saturation point 40klux). Especially the tomato need more than 6 hours dark period in total by a day. If it is shorter. it will have yel10w leaves according to its growing and soon die. The scion and stock are heavy injured living bodies, when they are processed. They need to restructure both own bodies by their propagating cells and to keep bOlh own lives , until joining perfectly. Therefore, they need the optimum aeclimation environment for their quality. This study is on the optimization of acclimating environment after grafting 10 keep the activity
of grafted seedlings, to shorten acclimation period, to maximize the production potential of seedlings, 2. A NEW ACCLlMA TION METHOD We have been trying to acclimate under the condition not only for the purpose of keeping the activity of seedlings by decreasing their transpiration and their respiration and spending of their energy, but also for the purpose of increasing the activity of seedlings by active photosynthesis. Its condition was 20'C(air temp.) , 90%(R.H), 6hours(light and dark interval period), 7klux (light intensity : tomato, eggplant). It took about 5days under this condition to finish acclirnating perfectly. This is 2days shorter than conventional methcxl. But we think that the degree of joining between the scion and the stock is increasing according to spend time. so there is each
956
optimum acclimation environment in every growth stage of seedlings from the time of grafting to the time of joining perfectly. and also we think that to put grafted seedlings under the each optimum acc1imation environment, we can fastest get the best seedlings. So it is necessary fOT propagating cells to product energies by the photosynthesis, but it is necessary for acting photosynthesis to provide water, C02 gas and physical environment such as temperature. relative humidity, light, wind and so on. It is most important for grafted seedlings which have been jointed, to provide water from the stock to the scion and keep moisture content inside the scion. Because the scion has not roots but leaves and it has to breathe with transpiration, while the stock has many roots and two cotyledons and it can get enough water from soil but it can produce least energy by photosynthesis of two cotyledons. So jointed seedlings have to been under the environment which can be low transpiration and high photosynthesis, We have to make this condition clear. Therefore if the moisture con lent inside the scion is decreasing, it is wilting. I propose that the degree of wilting utilized trigger signal which can decide the timing of switch for the photosynthesis. And its switch is turned on or off by the environment which is mainly intensity of light and concentration of CO~ gas. I am going to optimize the acclimation environment ~f grafted seedlings by controlling with light and CO,condition. In this time as thLe first step of this study, we investigated how the light intensity and the interval of light and dark period effect the degree of joining both the scion and the stock. While we are going to fabricate the measuring system which can acquire the wilting degree of a grafted seedling. Further more wc fabricated a simple physical model which could explain the wilting phenomenon of a seedling. 3. ACCLIMATION EXPERIMENT BY LIGHT INTENSITY AND ITS INTERVAL 3. J Plant materials We use the scions whose species is called "Momotarou" and the stocks whose species is called "LS89". The growth method of seedlings for grafting is as foHows. The seeds is put by each one into the soil which is called "System soil 102" made by Iwatani Co.ltd and is mixed with 10 Q water for a hour by the mixer and is put into the plug cell tray (200 holes). And we were growing them at 20-25'C in the greenhouse for about 30-40 days. Their irrigation was used the method of bottom one and its time interval was controlled by both the timer and the drying degree. We can get the scions and the stocks which is shown Fig. 1.
Fig. I. Tomato seedlings for grafting 3.2 Grafting method The conventional grafting methods are cutting grafting, cleft grafting and so on(Fig. 2). But we use the "Plug-in Method" which we first proposed in the world and satisfies the conditions in the view of plant histological and physiological standpoints. And the shape of "Plug-in Method" is as follows; for the scion, a stem will be shaped up as a form of plug like a pencil-tip, for the stock, a stern will be drilled to make a conical hole. This shape can be processed not by human hand but the special m!lchine.
The conventionaJ methods a) Cutting grafting b) Cleft grafting
Anewmethod c) Plug-in Method
Fig. 2. The grafting methods 3.3 Acclimation apparatus We fabricate the acclimation apparatus which consists of light system and water bath and plant bed (Fig.3). The light system uses the fluorescent light which is 96W, 3 intensity wave length. The water bath can be controlled temperature by 200W electric heater. The plant bed is covered with transparent box made of acrylic acid resin. The bottom of this box is opened and faced the water with heater. The plant bed is on the net rack over the water. More over there is a the larger box oUlside of this box with the air cooler. The light system is on the larger box. We try to control the temperature, humidity, brightness by the heat of the water heater, the air cooler, and the light system, and the difference between water temperature and air one, and brightness of the light system.
957
Light system
I~
"/,, /'-rA~~v • ••• • I
Heater Net
l
Cooler
I
Fig.4. The pull tester to measure the joining strength between the scion and the stock
I
1000
~ 800
Fig. 3. Acclimattion apparatus
"
~" 600
3.4 Experimental Conditions At firs t we set the three kinds o [ light intensity conditiuns(6.8klux, l.4klux, Oklux), and keep the waler temperature 28'C and ai r one 25-26·C. As a standard control. the stock which is not grafted was investigated in acclimation environment. More over we set 5 kinds of the interval of brightness and dark period whose rate is 12hours by 12hours, 6hours by 6hours, 3hours by 3hours, Ihour by 3hours (brightness time by dark onc). 3.5 Evaluatiou method We have to evaluate how the scio n and the stock are joined. So that we use the pull tester to measure the joining strength between the scion and the stock. The speed of pulling the grafted seedlings is con
"u
~ .;;; ..:"
I
400 200
j
0
2
/
345 Time (sec)
6
Fig.5 . A sample data which is variation of resistance force from the start of pulling to end in Method grafting has the 0.67 times strength than nongrafted one. Next the Fig.6 shows the rel ati onships among the light intensity and the interval of light and dark period and a strength of joining which indicates the degree of joining both the scion and the stock and is what the maximum value measured 72 hours ago after grafting, is standardized by the squares of its cross section. The numbers of samples for one time are 6 seedlings. We do such a experiment 5 times and in Fig.6, the average of them are shown as a form of ratio data when the strength value in the dark case is taken I. The strength of joining appeared in the case of 1.4 klux brightness stronger than in the dark case under the every interval condition . From these experimental results ,
Table 1. The results or joining strength in every grafting method Grafting method
Non
Clefl
Plug-in
Strength of joining (g/mm'l )
219
lOO
148
958
seedling from the degree its wilting phenomenon. But as the yellowing phenomenon which caused by the reason of both the brightness and Jiule moisture content inside a leaf appears after the long time as a fonn of accumulated under the enviro nment, the yellowi ng phenomeno n is very sensitive signal but it has late response. If we use the yellowing phenomenon as the moisture content variation, we need the more sensitive sensor which can measure the least variation of a leaf color. But I think that it is very difficult. So I decided that I tri ed to utilize the degree of wilting as a trigger signal which could decide the timing of switch for the photosynthesis. Next I show the method how the moisture content is explained by the degree of wilting.
1·1
Time interval(hour)
4 . MODELING METHOD FOR WILTING OF A SEEDLING Fig.6. The relationships among the light intensity and the interval of light and dark period and a strength of joining Table 2. The relationships among the interval of light and dark period and the degree of willing and the degree of yellowing Time interval (bright hour
Degree of wilting
by dark one)
The ligth intensiry(klux)
6.8 12by 12 6by 6 3by 3
Degree of yellowing
lA
0
6.8
1.4
0
3.8
0
0
4.0
3.3
0
3.4 J.3
0 0 0 0
3.3 2.7 3.4 1.3
2.0
0 0 0 0
I by
3.8
0 0 0
1 by 3
1.2
0
1.3
0.0 0.0
we found that especially the interva l of brightness and dark period whose rate was 6hours by 6hours or Ihour by lhour was effective. Furthermore, Table 2 shows the results of our investigation about the relationships among the interval of light and dark period and the degree of willing and the degree of yellowing. Both of degrees were decided by observation and were expressed with 5 ranges which are as follows; 0 is nothing, I is least, 2 is liltle, 3 is middle, 4 is much, 5 is dead. nle values in the table show the average of samples. The wilting phenomenon could not clearly be rec og nized under the l.4 klux bright condition. While under the 6.8 klux bright condi tion, we could observe wilting phenomenon. But the yellowing phenomenon could never be rec ogni zed on ty two cases which are I hour by 1hour and 1hour by 3hours. The moi stu re content becomes a shortage until one hour under the 1,4 klu x bright condition. until three hour s under the 6.8 klux bright condition. Surely we can get the moi sture content inside a
4. J Characteristics of materials The wilting behavior is depended upon not only the moislure conlenl of a seedling but also its rigidness and its size and so on. The older seedlings have rigid tissues and when it is wilting. its posture does not alter at all. So we have to get the rigidness information of a seedling that we fabricate the measuring system which can measure the rigidnes s as the re sista nce force at the constant speed cutting its stern. Fig.7 shows the rigidness measuring system. And it consi sts of the push tesler which is to measure the resistance force, the function generator which is the sampling liming timer, the digital sto rage scope which is to store data, and the computer which is to record. The method of measurement is as follows. We measure the resistance force by compressing the stem of seedlings perpendicular to the lengthwise of the stem fixed on the table until it is cut completely at the constant speed of 0.6 mm/sec with the two edge type cutter knife.
11
1E:j~. & .-' , i l'ooQ" oo.0 2.~1 1[J '[=-.:'.·::! ;~o~':~ [-- ... W.l1i.\.~
: I. •L - . ..C') ·()OO~'::;~ 00 1 C)
~
0
Fig.? The rigidness measuring system
4.2 Measuring apparatus for Wilting and moistllre At fist we treat a si ngle seedling. If to do so, Ihe degree of wilting can be expressed by the position of a leaf. So that
959
Seedling
Monitor Ligbt
Video system Phytotron
Fig.S. The wilting measuring system
we fabricate the measuring system which is shown in Fig.S. The variation of moisture is measured by using the electric balance. The position of a leaf is measured by using the CCD camera and the video system. Then the wilting phenomenon is acquired hy observation from horizontal direction. And secondly we trcat a canopy. If to do so, we get the change by observation from vertical direction. The decreasing moisture content inside a seedling is done by the water stress at irs root.... 4. 3 Mode/ing Fig.9 indicates the physical wilting model that we propose. This seedling mode l is expressed next equation which contain the apparent synthetic spring constant.
4.4 Results and discllssions The structure of stem is constructed with many layers in the form of a concentric circle, in which epidennis. variable soft cells, sieve tube, cambium, vessel, variable soft cell are located in order from o utside into inside. This vascular hundle tissue can hold very strong tensile force in the vertical direction. Both or them have soft tissues constituted relatively large cells and also contain hard cells cons tituted fiber cens such as epidermis. The vasc ular bundles co ntained vesse l and sieve tube and cambium. Most of the cell sizes in these four kinds of stems are 0.050.1 mm in diameter and more than 0.05 mm in average.The important physical propenies for cutting are such as the structure within a stem and the crispiness depending on moisture content or its growth stage. Especially a stem of eggplant has lots of very hard vascular bundles. But we can control so m e parts of its physical properties by environmental control during growing seedlings. Fig.1O shows a result obtained from the typical samples. The first peek appears by break of the epidermal tissue and distortion or strain due to compression. The resistance forcc comes larger gradually. There are a few peeks which are mainly caused by distortion and strain in cutting many hard tissues contained in the vascular bundle. Finally resistance force is reduced gradually while the stem is bei ng cut. In the view of the hardness. the dynamic cutting is occurred in the case of a hard s tem , otherwise the static cutting is occurred in a soft one. So we can observe the large strain in cutting soft one. 600
The second leaf -r----,r---r B
~ 500
$
8 400 c
~ 300
.~
~ 200
eo c 'il lOO ~
U
0+--yL-.-~--'-~--~--r-~~~. 2
· t OO
"-
kA(ro), ks(ro) : apparent synthetic spring constants
Fig.9. The physical wilting model y=-4 • m(w) , g/k(w) y : The position of a leaf (mm)
m(w) : The weight of a leaf (g) w : The moisture conte nt (Oh,)
g : The gravitational acceleration (m/sec1) k(w) : The apparent synthetic spring constant(N/m)
3
4
5
6
7
8
9
Time (sec)
Fig.IO. A result of resistance force
Fig. 11 shows a result of wilting and it is expressed the vertical position of the leaf lead. This position is falling down according to decreasing moisture content. The wave form looks like the sigm oid function. So that we found the next relationships between the moisture content and the leaf position as shown Table 3. We could get a equation which can be explain the wilting phenomenon. We will have 10 investigate the relationships between the properties of plant material and parameters in this equation.
960
140
120 .-.100
!
80
o
:~
60
g
40
lO , -~---~---.------~~ °9+0----~ 93 92.. S 92 91.5 91 90.S Moisture content(% )
Fig. l 1. A Tesull of willing Table 3. The relationships between the moisture conlent and the leaf position Eq\Ialilln
I
So.myIIe A , ,
S• • B
y" a( l+1f The ..
.,O
Pars'!'!!Ii.! _
•
(I':~ --i.&954~ -fI'
,,, le,,
TholiC\:ol'Llleaf
..
Tbt lirsl lul The r.e.:ond te.1
. ,ii:997058:7
"".
0.991U552
·tH71H
79.:f%.l i
-4:o:tt"I2
(l.!1.11 74s1
:~41.n9
~1 .6~~;:;~)
- :~~(). ::I!IH
O.99:~79fi
5. CONCLUSION As a result, we could find that the acclimation environ ment could be optimiz ed by the pholosyolhesis interval control. The wilting model we proposed is not good enough for explain ing the wilting phenom enon still now. But if we
correct this model , il can be useful for the accJimalion environ mem control.
961
Copyright@ 1996IFAC 131h Triennial World Congress. San Francisco. USA
ACCLIMA TlON ENVIRONMENT CONTROL AFfER GRAFTING - A NEW ACCLIMATlON METHOD-
Y.Nishiura, RMurase, N.Honanti
Lab, of Rioinstrumentation, Control and Systems Engineering Department of Regional Environmental Science. Faculty of Agricullur(~ UniversilyofO.,aka Prefeclure, I-I Gakuen-cho, Sakai, Osaka 593, JAPAN
Abstract: The production system for grafted seedlings consists of mainly three parts. Onc is the growing process, another one is the grafting process, and the last onc is the acc1imation process, The acc1imation process is very important for grafted seedlings because they arc seriously injured. The qualities of seedlings and the management of farmers and seedling producers depend upon the acclimating technologies. Now, we are trying to develop such a grafting robot system which satisfies the conditions in the view of plant histological and physiological standpoints. In this study we show a new acclimation method on the basis of high technologies. Keywords: Photosynthesis interval , Acclimation environment control. Wilting behavior. Machine vision technique. Bioinstrumentation. Wilting model. Grafting robot system, Bioproduction
I. INTRODUCTION
In general, it is necessary for acc1imating grafted seedlings to spend for about 70r 10 days under the conditions of 2528'C(air temp _) , 90%(R. H) , 12hours(light and dark interval period), 5klux (light intensity : tomato: light saturation point 70klux), 3klux (light intensity: eggplant, watermelon; light saturation point 40klux). Especially the tomato need more than 6 hours dark period in total by a day. If it is shorter. it will have yel10w leaves according to its growing and soon die. The scion and stock are heavy injured living bodies, when they are processed. They need to restructure both own bodies by their propagating cells and to keep bOlh own lives , until joining perfectly. Therefore, they need the optimum aeclimation environment for their quality. This study is on the optimization of acclimating environment after grafting 10 keep the activity
of grafted seedlings, to shorten acclimation period, to maximize the production potential of seedlings, 2. A NEW ACCLlMA TION METHOD We have been trying to acclimate under the condition not only for the purpose of keeping the activity of seedlings by decreasing their transpiration and their respiration and spending of their energy, but also for the purpose of increasing the activity of seedlings by active photosynthesis. Its condition was 20'C(air temp.) , 90%(R.H), 6hours(light and dark interval period), 7klux (light intensity : tomato, eggplant). It took about 5days under this condition to finish acclirnating perfectly. This is 2days shorter than conventional methcxl. But we think that the degree of joining between the scion and the stock is increasing according to spend time. so there is each
956
optimum acclimation environment in every growth stage of seedlings from the time of grafting to the time of joining perfectly. and also we think that to put grafted seedlings under the each optimum acc1imation environment, we can fastest get the best seedlings. So it is necessary fOT propagating cells to product energies by the photosynthesis, but it is necessary for acting photosynthesis to provide water, C02 gas and physical environment such as temperature. relative humidity, light, wind and so on. It is most important for grafted seedlings which have been jointed, to provide water from the stock to the scion and keep moisture content inside the scion. Because the scion has not roots but leaves and it has to breathe with transpiration, while the stock has many roots and two cotyledons and it can get enough water from soil but it can produce least energy by photosynthesis of two cotyledons. So jointed seedlings have to been under the environment which can be low transpiration and high photosynthesis, We have to make this condition clear. Therefore if the moisture con lent inside the scion is decreasing, it is wilting. I propose that the degree of wilting utilized trigger signal which can decide the timing of switch for the photosynthesis. And its switch is turned on or off by the environment which is mainly intensity of light and concentration of CO~ gas. I am going to optimize the acclimation environment ~f grafted seedlings by controlling with light and CO,condition. In this time as thLe first step of this study, we investigated how the light intensity and the interval of light and dark period effect the degree of joining both the scion and the stock. While we are going to fabricate the measuring system which can acquire the wilting degree of a grafted seedling. Further more wc fabricated a simple physical model which could explain the wilting phenomenon of a seedling. 3. ACCLIMATION EXPERIMENT BY LIGHT INTENSITY AND ITS INTERVAL 3. J Plant materials We use the scions whose species is called "Momotarou" and the stocks whose species is called "LS89". The growth method of seedlings for grafting is as foHows. The seeds is put by each one into the soil which is called "System soil 102" made by Iwatani Co.ltd and is mixed with 10 Q water for a hour by the mixer and is put into the plug cell tray (200 holes). And we were growing them at 20-25'C in the greenhouse for about 30-40 days. Their irrigation was used the method of bottom one and its time interval was controlled by both the timer and the drying degree. We can get the scions and the stocks which is shown Fig. 1.
Fig. I. Tomato seedlings for grafting 3.2 Grafting method The conventional grafting methods are cutting grafting, cleft grafting and so on(Fig. 2). But we use the "Plug-in Method" which we first proposed in the world and satisfies the conditions in the view of plant histological and physiological standpoints. And the shape of "Plug-in Method" is as follows; for the scion, a stem will be shaped up as a form of plug like a pencil-tip, for the stock, a stern will be drilled to make a conical hole. This shape can be processed not by human hand but the special m!lchine.
The conventionaJ methods a) Cutting grafting b) Cleft grafting
Anewmethod c) Plug-in Method
Fig. 2. The grafting methods 3.3 Acclimation apparatus We fabricate the acclimation apparatus which consists of light system and water bath and plant bed (Fig.3). The light system uses the fluorescent light which is 96W, 3 intensity wave length. The water bath can be controlled temperature by 200W electric heater. The plant bed is covered with transparent box made of acrylic acid resin. The bottom of this box is opened and faced the water with heater. The plant bed is on the net rack over the water. More over there is a the larger box oUlside of this box with the air cooler. The light system is on the larger box. We try to control the temperature, humidity, brightness by the heat of the water heater, the air cooler, and the light system, and the difference between water temperature and air one, and brightness of the light system.
957
Light system
I~
"/,, /'-rA~~v • ••• • I
Heater Net
l
Cooler
I
Fig.4. The pull tester to measure the joining strength between the scion and the stock
I
1000
~ 800
Fig. 3. Acclimattion apparatus
"
~" 600
3.4 Experimental Conditions At firs t we set the three kinds o [ light intensity conditiuns(6.8klux, l.4klux, Oklux), and keep the waler temperature 28'C and ai r one 25-26·C. As a standard control. the stock which is not grafted was investigated in acclimation environment. More over we set 5 kinds of the interval of brightness and dark period whose rate is 12hours by 12hours, 6hours by 6hours, 3hours by 3hours, Ihour by 3hours (brightness time by dark onc). 3.5 Evaluatiou method We have to evaluate how the scio n and the stock are joined. So that we use the pull tester to measure the joining strength between the scion and the stock. The speed of pulling the grafted seedlings is con
"u
~ .;;; ..:"
I
400 200
j
0
2
/
345 Time (sec)
6
Fig.5 . A sample data which is variation of resistance force from the start of pulling to end in Method grafting has the 0.67 times strength than nongrafted one. Next the Fig.6 shows the rel ati onships among the light intensity and the interval of light and dark period and a strength of joining which indicates the degree of joining both the scion and the stock and is what the maximum value measured 72 hours ago after grafting, is standardized by the squares of its cross section. The numbers of samples for one time are 6 seedlings. We do such a experiment 5 times and in Fig.6, the average of them are shown as a form of ratio data when the strength value in the dark case is taken I. The strength of joining appeared in the case of 1.4 klux brightness stronger than in the dark case under the every interval condition . From these experimental results ,
Table 1. The results or joining strength in every grafting method Grafting method
Non
Clefl
Plug-in
Strength of joining (g/mm'l )
219
lOO
148
958
seedling from the degree its wilting phenomenon. But as the yellowing phenomenon which caused by the reason of both the brightness and Jiule moisture content inside a leaf appears after the long time as a fonn of accumulated under the enviro nment, the yellowi ng phenomeno n is very sensitive signal but it has late response. If we use the yellowing phenomenon as the moisture content variation, we need the more sensitive sensor which can measure the least variation of a leaf color. But I think that it is very difficult. So I decided that I tri ed to utilize the degree of wilting as a trigger signal which could decide the timing of switch for the photosynthesis. Next I show the method how the moisture content is explained by the degree of wilting.
1·1
Time interval(hour)
4 . MODELING METHOD FOR WILTING OF A SEEDLING Fig.6. The relationships among the light intensity and the interval of light and dark period and a strength of joining Table 2. The relationships among the interval of light and dark period and the degree of willing and the degree of yellowing Time interval (bright hour
Degree of wilting
by dark one)
The ligth intensiry(klux)
6.8 12by 12 6by 6 3by 3
Degree of yellowing
lA
0
6.8
1.4
0
3.8
0
0
4.0
3.3
0
3.4 J.3
0 0 0 0
3.3 2.7 3.4 1.3
2.0
0 0 0 0
I by
3.8
0 0 0
1 by 3
1.2
0
1.3
0.0 0.0
we found that especially the interva l of brightness and dark period whose rate was 6hours by 6hours or Ihour by lhour was effective. Furthermore, Table 2 shows the results of our investigation about the relationships among the interval of light and dark period and the degree of willing and the degree of yellowing. Both of degrees were decided by observation and were expressed with 5 ranges which are as follows; 0 is nothing, I is least, 2 is liltle, 3 is middle, 4 is much, 5 is dead. nle values in the table show the average of samples. The wilting phenomenon could not clearly be rec og nized under the l.4 klux bright condition. While under the 6.8 klux bright condi tion, we could observe wilting phenomenon. But the yellowing phenomenon could never be rec ogni zed on ty two cases which are I hour by 1hour and 1hour by 3hours. The moi stu re content becomes a shortage until one hour under the 1,4 klu x bright condition. until three hour s under the 6.8 klux bright condition. Surely we can get the moi sture content inside a
4. J Characteristics of materials The wilting behavior is depended upon not only the moislure conlenl of a seedling but also its rigidness and its size and so on. The older seedlings have rigid tissues and when it is wilting. its posture does not alter at all. So we have to get the rigidness information of a seedling that we fabricate the measuring system which can measure the rigidnes s as the re sista nce force at the constant speed cutting its stern. Fig.7 shows the rigidness measuring system. And it consi sts of the push tesler which is to measure the resistance force, the function generator which is the sampling liming timer, the digital sto rage scope which is to store data, and the computer which is to record. The method of measurement is as follows. We measure the resistance force by compressing the stem of seedlings perpendicular to the lengthwise of the stem fixed on the table until it is cut completely at the constant speed of 0.6 mm/sec with the two edge type cutter knife.
11
1E:j~. & .-' , i l'ooQ" oo.0 2.~1 1[J '[=-.:'.·::! ;~o~':~ [-- ... W.l1i.\.~
: I. •L - . ..C') ·()OO~'::;~ 00 1 C)
~
0
Fig.? The rigidness measuring system
4.2 Measuring apparatus for Wilting and moistllre At fist we treat a si ngle seedling. If to do so, Ihe degree of wilting can be expressed by the position of a leaf. So that
959
Seedling
Monitor Ligbt
Video system Phytotron
Fig.S. The wilting measuring system
we fabricate the measuring system which is shown in Fig.S. The variation of moisture is measured by using the electric balance. The position of a leaf is measured by using the CCD camera and the video system. Then the wilting phenomenon is acquired hy observation from horizontal direction. And secondly we trcat a canopy. If to do so, we get the change by observation from vertical direction. The decreasing moisture content inside a seedling is done by the water stress at irs root.... 4. 3 Mode/ing Fig.9 indicates the physical wilting model that we propose. This seedling mode l is expressed next equation which contain the apparent synthetic spring constant.
4.4 Results and discllssions The structure of stem is constructed with many layers in the form of a concentric circle, in which epidennis. variable soft cells, sieve tube, cambium, vessel, variable soft cell are located in order from o utside into inside. This vascular hundle tissue can hold very strong tensile force in the vertical direction. Both or them have soft tissues constituted relatively large cells and also contain hard cells cons tituted fiber cens such as epidermis. The vasc ular bundles co ntained vesse l and sieve tube and cambium. Most of the cell sizes in these four kinds of stems are 0.050.1 mm in diameter and more than 0.05 mm in average.The important physical propenies for cutting are such as the structure within a stem and the crispiness depending on moisture content or its growth stage. Especially a stem of eggplant has lots of very hard vascular bundles. But we can control so m e parts of its physical properties by environmental control during growing seedlings. Fig.1O shows a result obtained from the typical samples. The first peek appears by break of the epidermal tissue and distortion or strain due to compression. The resistance forcc comes larger gradually. There are a few peeks which are mainly caused by distortion and strain in cutting many hard tissues contained in the vascular bundle. Finally resistance force is reduced gradually while the stem is bei ng cut. In the view of the hardness. the dynamic cutting is occurred in the case of a hard s tem , otherwise the static cutting is occurred in a soft one. So we can observe the large strain in cutting soft one. 600
The second leaf -r----,r---r B
~ 500
$
8 400 c
~ 300
.~
~ 200
eo c 'il lOO ~
U
0+--yL-.-~--'-~--~--r-~~~. 2
· t OO
"-
kA(ro), ks(ro) : apparent synthetic spring constants
Fig.9. The physical wilting model y=-4 • m(w) , g/k(w) y : The position of a leaf (mm)
m(w) : The weight of a leaf (g) w : The moisture conte nt (Oh,)
g : The gravitational acceleration (m/sec1) k(w) : The apparent synthetic spring constant(N/m)
3
4
5
6
7
8
9
Time (sec)
Fig.IO. A result of resistance force
Fig. 11 shows a result of wilting and it is expressed the vertical position of the leaf lead. This position is falling down according to decreasing moisture content. The wave form looks like the sigm oid function. So that we found the next relationships between the moisture content and the leaf position as shown Table 3. We could get a equation which can be explain the wilting phenomenon. We will have 10 investigate the relationships between the properties of plant material and parameters in this equation.
960
140
120 .-.100
!
80
o
:~
60
g
40
lO , -~---~---.------~~ °9+0----~ 93 92.. S 92 91.5 91 90.S Moisture content(% )
Fig. l 1. A Tesull of willing Table 3. The relationships between the moisture conlent and the leaf position Eq\Ialilln
I
So.myIIe A , ,
S• • B
y" a( l+1f The ..
.,O
Pars'!'!!Ii.! _
•
(I':~ --i.&954~ -fI'
,,, le,,
TholiC\:ol'Llleaf
..
Tbt lirsl lul The r.e.:ond te.1
. ,ii:997058:7
"".
0.991U552
·tH71H
79.:f%.l i
-4:o:tt"I2
(l.!1.11 74s1
:~41.n9
~1 .6~~;:;~)
- :~~(). ::I!IH
O.99:~79fi
5. CONCLUSION As a result, we could find that the acclimation environ ment could be optimiz ed by the pholosyolhesis interval control. The wilting model we proposed is not good enough for explain ing the wilting phenom enon still now. But if we
correct this model , il can be useful for the accJimalion environ mem control.
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