Study
on the application of lanthanum-rhodamine doped polyethylene film in photosynthesis
Zhang Keli, Yuan Liangjie, Xi Meiyun, Sun Jutang
(College of Chemistry and Molecular Sciences, Wuhan University, Wuhan 430072, China)
Received: Nov. 5, 2001; Supported by the
National Natural Science Foundation of China (No.20071026).
Abstract Lanthanum-rhodamine (6G and B)
complexes were synthesized by Rheological Phase Reaction Method. Lanthanum-rhodamine (6G
and B) complexes doped polyethylene films were prepared. The emission and excitation
spectra were measured. The experiments of growing seedling and culture were carried out in
the shed built with doped and undoped polyethylene films. Lanthanum-rhodamine doped
polyethylene films can efficiently convert the green light in the sunlight to the red
light for photosynthesis of crops, promote the maturing of crops and raise the yield of
crops.
Keywords Lanthanum; Photosynthesis; Polyethylene film; Rhodamine; Rheological
phase reaction.
Rhodamine 6G and its
derivatives have been used in wide domain.[1] Recently, the complexes of
rhodamine 6G have also aroused considerable interest.[2,3] It is found that the
rare earth complexes of rhodamine 6G and B have better luminescence properties. As kinds
of optical conversion materials, its can be used in growing of plants.
It is well known that polyethylene (PE) film used
in agriculture can keep up the soil temperature and soil moisture to improve the growing
conditions of crops, and enable grain, cotton and vegetables to increase yields. Many
optical frequency conversion materials doped PE films can change inefficient light in
sunlight into efficient light for photosynthesis of crops, promote the maturing of crops
and raise the yield of crops.
In this work, the lanthanum-rhodamine (6G and B) complexes and
lanthanum-rhodamine doped polyethylene films were prepared. The experiments of growing
seedling and culture of crops and vegetables were carried out in the shed built with doped
and undoped polyethylene films.
1 EXPERIMENTAL
The complexes of rhodamine 6G and rhodamine B with lanthanum were prepared from rhodamine
6G, rhodamine B and lanthanum hydroxide by the rheological phase reaction method.[4,5]
The lanthanum rhodamine 6G (LRG) and lanthanum rhodamine B complexes (LRB) doped PE films
were prepared with the same method as preparing PE film. The amount of LRG and LRB doped
is 0.2%, respectively. The emission and excitation spectra were obtained with a Shimadzu
RF-5000 spectrofluorophotometer. The growing seedling and culture of crops and vegetables
were experimented in the shed built with the LRB-doped PE films, and a control experiment
with undoped PE film was carried out in the same conditions. The seedbed is 44 m long,
1.33 m wide. The height of the shed is 0.3 m. One experiment area is 10 m long. Two
parallel experiments were carried out. In the shed, the thermometers were installed
underground (5cm depth) and on the earth's surface, separately. The temperature in the
sheds was observed at 8, 14, and 18 per day on time.
2
RESULTS AND DISCUSSION
The LRB-doped PE films have very strong red luminescence excited by
sunlight. The excitation and emission spectra of the LRB-doped PE films are shown in
Fig.1. Peaks located at 555 and 580nm are assigned to the emission bands of LRB-doped PE
films, respectively. The broad peaks from 470 to590nm are due to the excitation bands. It
is showed that the LRG- and LRB-doped PE films can transfer the green light in sunlight to
the efficient red light which photosynthesis of crops needs.
The differences of temperature in the sheds made with two kinds of
films are listed in table 1. In the shed with LRB-doped PE film, in sunny day, the
temperature of soil surface increased by 1 to 2 degrees, and by 2 to 4.5 degrees 5 cm deep
under the mud, compared with that in the shed with undoped PE film. In overcast sky and
cloudy day, the temperature increased by 1 to 1.5 degrees in the surface and by 1.5 to 2.5
degrees 5 cm deep under the mud. The difference of soil temperature in the shed with
LRB-doped PE film is great in day and night, it is advantageous to the growing of
seedlings. In addition, these films have better function of ventilation, and can prevent
the seedling from rotting.
Intensity (a.u) |
|
Fig.1
The excitation (a) and emission (b) spectra of the LRG (solid line) and LRB (dotted line)
doped PE films
Table 1 The
temperature in the sheds made with two kinds of films
Material |
Temperature (degree) in sunny day at 2 p.m. |
soil surface |
5 cm deep under the mud |
PE film |
20.8 |
21.8 |
LRB- doped PE film |
21.8 |
26.3 |
Table 2 The results of
the rate of sprouting *
Material |
Rate of sprouting (%) |
cotton |
cucumber |
tomato |
PE film |
87 |
15 |
5 |
LRB- doped PE film |
163 |
153 |
78 |
* Seeds were
sowed on March 28, the rates of sprouting were examined after 15 days
The experimental results of
rate of sprouting are listed in table 2. Within 11 days (the seeds were sowed on March 28)
the rate of sprouting showed that cotton was 90% higher than that of the undoped PE film,
cucumber 9-fold and tomato 10-fold, respectively. Cotton was sowed on April 10, after 6
days the rate of sprouting is 85.5%, it is 10.9% higher than that of the undoped PE film.
The growth speed of cotton seedling increased by 23%.
The output of crop and vegetables cultivated in the same fields after
growing seedlings in different films are listed in table 3. The experimental results of
cultivation by growing seedlings, the average values of three repeated experiments,
indicate that the output of cotton go up more than 10%, winter lettuce 29%, zicaitai about
40%, hot pepper about 60%.
Table 3 The
results of the output of crop and vegetables *
Material |
Output (kg/ha) |
Cotton |
Winter lettuce |
Zicaitai |
Hot pepper |
PE
film |
2250 |
15975 |
16410 |
7500 |
LRB-
doped PE film |
2475 |
20625 |
22980 |
12000 |
* In the same conditions
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[2] Wang H, Xiong R G, Liu C M et al. Inorg Chim Acta, 1997, 254 (1): 183.
[3] Liu C M, Xiong R G, You X Z et al. Acta Chemica Scandinavica, 1998, 52 (7): 883.
[4] Sun J T, Yuan L J, Zhang K L et al.
Materials Science and Engineering, 1999, B64: 157.
[5]Zhang K L, Yuan L J, Sun J T et al. J Wuhan Univ, 2000, 46 Special Issue (1):
306.
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