Effects of supplemental UV-B radiation on the growth and yield of
two cultivars of Japanese lowland rice (Oryza sativa L.) under the
field in a cool rice-growing region of Japan
Tadashi Kumagai
∗, Jun Hidema, Hye-Sook Kang, Tadashi Sato
Institute of Genetic Ecology, Tohoku University, Katahira, Aoba-ku, Sendai 980-8577, Japan
Received 20 July 1999; received in revised form 24 February 2000; accepted 17 May 2000
Abstract
An investigation was made of the variations in growth and grain yield in response to increased exposure to UV-B radiation of Japanese lowland rice (Oryza sativa L.) in a cool rice-growing region. Two cultivars, UV-resistant cv. ‘Sasanishiki’ and UV-sensitive cv. ‘Norin 1’, were examined in a lowland field at Kashimadai (37◦28′E, 141◦06′E) in Miyagi Prefecture, Japan,
for four cropping seasons from 1994 to 1997. The two cultivars were grown in a lowland field with or without supplemental UV-B radiation, which was provided by UV-B-emitting fluorescent lamps, with a 0.1-mm-thick cellulose diacetate film as a filter. In both cultivars, significant decreases in tiller number as the result of supplemental UV-B radiation were observed during the tillering stage in 1994, 1995 and 1997. Furthermore, decreases in grain size from supplemental UV-B radiation were recorded in all seasons. The trend towards small grain size was pronounced in 1996. In that year, the mean daily middle temperatures were lower throughout most of the cropping season and the mean daily hours of sunshine during the tillering stage and between the end of the panicle differentiation stage and the beginning of the ripening stage were shorter. In 1993 when the temperature and the amount of sunshine were both lower, the tiller number, the dry mass of aboveground parts and the panicle number were significantly reduced by supplemental unfiltered UV-B radiation. There was a cultivar difference in the inhibitory effects of supplemental UV-B radiation on growth between the sensitive cultivar Norin 1 and the resistant cultivar Sasanishiki.
These results indicate that supplemental UV-B radiation has a positive effect on the growth and grain development of rice, which may be enhanced by unusual climatic conditions such as lower temperature and less sunshine, in cool rice-growing regions. © 2001 Elsevier Science B.V. All rights reserved.
Keywords: Supplemental UV-B radiation; Rice; Cool rice-growing region; Field work; Growth and yield; Grain size; Japan
1. Introduction
The depletion of stratospheric ozone because of the emission of chlorofluorocarbons (CFCs) and other trace gases has resulted in increases in solar
∗Corresponding author. Tel.:+81-22-217-5688; fax:+81-22-263-9845.
E-mail address: kumagai@ige.tohoku.ac.jp (T. Kumagai).
ultraviolet-B (UV-B) radiation at the earth’s sur-face (Blumthaler and Ambach, 1990). Furthermore, measurements of global ozone obtained by satellites between 1979 and 1993 indicate significant increases in UV-B radiation at high and mid-latitudes in both hemispheres, with only small changes at low-latitudes (Madronich et al., 1995). The cited authors pos-tulated that recovery to earlier levels might occur gradually over the next 50 years. In Japan, higher
rates of increases in solar UV-B radiation have been recognized in Sapporo (43◦05′N) than in Tsukuba (36◦07′N) and Kagoshima (31◦35′N) (JMA, 1998).
Studies in greenhouses and growth chambers have shown that enhanced UV-B radiation has deleteri-ous effects on the growth and development of higher plants, as well as on photosynthesis (Teramura, 1983). Furthermore, the deleterious effects of enhanced UV-B radiation vary markedly within and among species (Tevini and Teramura, 1989). However, in sev-eral recent field studies, no decreases were recorded in leaf photosynthesis, stomatal conductance and plant growth after enhanced UV-B radiation (Rozema et al., 1997).
Short-term studies of plants at the seedling stage in growth chambers or greenhouses can be useful for investigations of physiological mechanisms and of differences in resistance to UV-B radiation among cultivars. However, experiments over many seasons under natural field conditions are necessary to assess differences in yield among cultivars exposed to en-hanced UV-B radiation because the effects of UV-B radiation on growth and yield are strongly influenced by seasonal microclimatic conditions. Teramura et al. (1990) examined the potential for changes in the yield and seed quality of soybean grown for six seasons in the field. They noted that it is necessary to per-form analyses over multiple seasons and to examine interactions between UV-B radiation and other envi-ronmental factors in order to assess accurately the po-tential consequences of stratospheric ozone depletion. Rice is one of the world’s most important staple food grains, and it is urgent to determine how rice growth and yield are affected by increasing UV-B radi-ation. Experiments in growth chambers have indicated significant variations among rice cultivars in terms of the effects of enhanced UV-B radiation on the pro-duction of aerial biomass (Teramura et al., 1991; Dai et al., 1992; He et al., 1993; Sato and Kumagai, 1993). By contrast, few field studies have examined the ef-fects of supplemental UV-B radiation on the growth and yield of rice. One such study was conducted for 1 year in 1993 in the temperate climate of Tsukuba in Japan (36◦01′N, 140◦07′E) (Kim et al., 1996) and two others were carried out for 2 years (from 1992 to 1993) (Dai et al., 1998) and 4 years (from 1992 to 1995) (Dai et al., 1997) in the tropical climate of the International Rice Research Institute (IRRI) in the
Philippines (14◦10′N, 121◦30′E). Negative effects of supplemental UV-B radiation on growth and yield un-der field conditions were demonstrated in both studies. However, the researchers indicated that there is a need to perform supplemental UV-B studies under different climates and latitudes, in which different cultivars are grown and where the UV-B regimes are quite different. The authors previously found that, in a growth chamber, the ‘Sasanishiki’ cultivar of Japanese low-land rice (one of the leading cultivars in the northern part of Japan) was more resistant to increased UV-B radiation than the ‘Norin 1’ cultivar, even though these two cultivars are closely related (Kumagai and Sato, 1992; Hidema et al., 1996). The northern region in Japan is close to the northern geographical limit of the range of rice production where cool tempera-tures and poor sunlight sometime decrease the yields. Cultivated rice evolved as a semi-aquatic plant in the humid environment of the tropics. Crops which originated in the tropics are susceptible to damage when temperatures and hours of sunshine fall below a critical threshold. Few field studies of the effects of increased UV-B radiation on the growth and yield of rice have been undertaken in cool rice-growing regions at middle latitudes.
In this study, two cultivars of Japanese lowland rice, Sasanishiki and Norin 1, were grown in a lowland rice field with or without supplemental UV-B radiation for five consecutive cropping seasons, to determine whether UV-B radiation affects vegetative growth and yield, and whether the sensitivity to enhanced UV-B radiation differs between these cultivars.
2. Materials and methods
2.1. Plant material and culture
conducted from late May though early October at the Experimental Farm Station of the Institute of Genetic Ecology, Tohoku University, at Kashimadai (37◦28′N, 141◦06′E) in Miyagi Prefecture, Japan. Basal fertil-izer, with slow release at rates of 30, 30 and 30 kg/ha (N, PO5 and K), was applied 3–7 days before
trans-planting. Each seedling was transplanted to a lowland field in late May, with one plant per hill and spacing of 15×30 cm between hills. This transplant density falls within the range of commonly used sowing den-sities in Northeast Japan. Fields were flooded just after the seedlings were transplanted and then kept submerged under 5–10 cm of water until the middle of August in 1994, 1995, 1996 and 1997. In 1993, fields were kept submerged under similar conditions until the middle of September. The method used for the culture of rice plants corresponded to common agronomic practices in the region.
2.2. Exposure to supplemental UV-B radiation
In 1993, UV-B radiation was supplied by UV-B emitting fluorescent tubes (FL 20SE; Toshiba Ltd. Co., Tokyo, Japan). This UV-B radiation included a small amount of UV-C with a ratio of the irradi-ance in the UV-B region to that in the UV-C region of 1:0.17. The irradiance in the UV region of the spectrum (313±30 nm) was measured with a data logger (L1-1000; Li-Cor, USA) with a UV sensor (SD104; Macom Co., UK.). The irradiance in the UV region of the supplemental UV radiation at the plant canopy ranged from 0.18 to 0.32 W/m2 depending on plant height. From 1994 to 1997, supplemental UV-B radiation was provided by UV-B fluorescent tubes with filtering through 0.1-mm-thick cellulose diacetate film (Cadillac Plastic Co., Baltimore, MD, USA), which absorbs UV radiation below 290 nm. The cellulose diacetate film was changed every 2 weeks to ensure uniformity of transmission prop-erties. The facilities for applying UV-B radiation consisted of eight sets of lamp frames. Each lamp frame (0.6 m×1.8 m) contained four UV-B fluores-cent lamps spaced 60 cm apart. The height of lamps above the plants was adjusted weekly to maintain a distance of 30 cm between the lamps and the tops of plants. Mean supplemental UV-B irradiance at the top of the plant canopy was 0.21 W/m2, as measured with a spectroradiometer (SS-25; Japan Spectroscopic
Co., Tokyo, Japan). The dose of biologically effective UV-B radiation (UV-BBE) was calculated from the
generalized plant action spectrum of Caldwell (1971), normalized to unity at 300 nm. The amount of supple-mental UV-BBE (kJ/m2/day) applied daily was 4.2.
Supplemental UV-B radiation in every experiment was applied from 6:00 a.m. to 6:00 p.m.
In control frames in all experiments, fluorescent tubes were removed from the fluorescent tube-holder to equalize the visible-light environment under the control and UV-B frames.
2.3. Measurements and statistical analysis of data
Rice plants within 0.6 m×1.8 m plots were ana-lyzed because UV-B irradiance was homogeneous to a distance of 30 cm beyond the edge of the UV-B fluorescent tubes. The tiller number and height of each plant were recorded eight weeks after transplan-tation. After harvesting, each plant was dried at room temperature to constant weight, and then divided into inflorescence and stem parts; the dry mass of each part was measured. Grains were classified by sift-ing through different sizes of mesh in electric sieves (S-type; Ooyatanzou Seisakusyo Co., Tokyo, Japan).
Results were analyzed separately for each cultivar for each season. Statistical comparisons were made between mean values per plot for UV-B treated and control plants using an unpaired t-test, with means separated by least significant differences (LSD). Sig-nificance was recognized at p<0.05. The data were analyzed with the EXCEL statistical analysis 97 package (SSRI Ltd. Co., Tokyo, Japan).
3. Results and discussion
Table 1
Mean daily middle temperatures and mean daily hours of sunshine during the rice cropping seasons from 1993 to 1997a
Periodb Mean daily middle temperature (◦C)c Mean daily hours of sunshine (h)
Averaged 1993 1994 1995 1996 1997 Averaged 1993 1994 1995 1996 1997
May Last 10 days 14.9 16.4 17.1 16.3 16.9 13.4 6.6 5.8 5.4 4.3 6.3 2.5
I June First 10 days 17.5 16.1 17.6 16.4 16.0 15.7 5.6 1.2 2.8 2.8 5.0 2.5
Middle 10 days 18.2 18.9 18.5 17.0 17.8 17.7 4.5 3.0 5.0 1.1 2.1 2.6 Last 10 days 19.2 18.8 18.3 17.6 18.0 21.0 3.7 2.2 2.3 0.5 0.8 4.7 July First 10 days 20.0 17.3 21.4 21.1 18.9 22.1 3.2 2.5 2.2 1.1 2.0 1.9
II Middle 10 days 21.7 17.9 23.8 21.4 22.6 21.4 3.6 0.1 6.0 2.3 4.3 5.0 Last 10 days 24.0 19.5 25.3 25.5 23.7 NDe 5.2 0.2 4.3 7.5 2.2 3.4
August First 10 days 24.5 18.4 27.1 20.4 21.7 25.4 5.7 1.5 6.5 2.4 4.1 5.1
III Middle 10 days 24.5 21.3 25.6 24.5 23.6 21.6 4.9 2.7 8.1 2.4 5.3 1.1
Last 10 days 23.5 22.7 23.3 26.3 20.1 22.0 4.5 5.0 4.5 2.2 2.2 6.2 September First 10 days 22.0 19.2 22.9 20.3 19.9 22.2 3.9 2.6 5.6 4.8 4.1 2.8 Middle 10 days 20.1 19.3 21.9 17.2 18.8 18.4 3.9 4.6 3.9 4.8 4.5 1.3
Last 10 days 18.1 17.0 18.3 18.1 16.7 15.6 4.3 3.0 2.0 5.2 5.4 1.7
aTable was constructed from the data of the Annual Report of the Miyagi Prefecture Meteorological Station (1993, 1994, 1995, 1996,
1997). Italicized letters in daily middle temperature and daily hours of sunshine indicate values that are lower by more than 1◦C and lower by more than half, respectively, than the mean values for the last 30 years.
bPeriod I (from 1 June to 10 July): the tillering stage in both cultivars. Period II (from 11 July to 10 August): the panicle differentiation
stage in both cultivars. Period III (from 11 August to 21 September): the ripening stage of seeds in both cultivars.
cDaily middle temperature: (daily maximum temperature+daily minimum temperature)/2.
dAverage: mean values of daily middle temperatures and daily hours of sunshine for the last 30 years. eNo data, due to problems of the facilities.
growing rice. Table 1 shows the mean daily middle temperatures and mean daily hours of sunshine of each 10-day period during the rice-cropping season from 1993 to 1997 and their average values for the last 30 years (1966–1996) according to the Annual Report of Miyagi Prefecture Meteorological Station. In the ta-ble, the mean daily middle temperatures lower than 1◦C of the average values of the last 30 years and the daily hours of sunshine <50% of the average values of the last 30 years are italicized. In 1993, the mean daily middle temperatures and the mean daily hours of sunshine were both lower, throughout most of the cropping season. By contrast, the mean daily middle temperatures and the mean daily hours of sunshine in 1994 were both slightly greater than the average values for the last 30 years throughout most of the cropping season except for the lower mean daily hours of sun-shine during the tillering stage. The mean daily mid-dle temperatures during the tillering stage and ripen-ing stage in 1995, 1996 and 1997 were lower than the average values of the last 30 years. Much lower mean daily hours of sunshine were observed during the tillering stage in 1995, 1996 and 1997, as well as
during the panicle differentiation stage in 1995 and 1996, and the ripening stage in 1995, 1996 and 1997. Table 2 shows the results of preliminary experi-ment made in 1993, when unfiltered UV-B radiation was used. Here, the percent change was based on the following equation: (value of sample−value of con-trol)/value of control×100%. Each parameter, namely, tiller number, dry mass of aboveground parts, culm length and panicle number was significantly lower in both cultivars grown under unfiltered UV-B radiation; the lower values of Norin 1 were particularly marked in comparison with the values for Sasanishiki. In Norin 1, the supplemental unfiltered UV-B radiation caused reductions of 41.6, 46.5, 12.8 and 26.5% in tiller num-ber, dry mass, culm length and panicle numnum-ber, re-spectively. In Sasanishiki, tiller number, dry mass and panicle number were reduced by 12.9, 28.2 and 12.6%, respectively.
Table 2
Effects of supplemental ultraviolet-B radiation on tiller number, dry mass, culm length and panicle number of two rice cultivars grown under lowland field conditions in 1993a
Parameter Sasanishiki Norin 1
Control Treated Change (%)b pf Control Treated Change (%)b p
Tiller numberc(No./plant) 21.0±2.8 18.3±2.8 −12.9 *** 22.0±3.8 12.9±3.6 −41.6 ***
Dry massd (g/plant) 50.9±8.7 36.5±8.8 −28.2 *** 48.4±9.7 25.9±5.2 −46.5 ***
Culm length (cm) 91.4±3.7 88.5±8.9 −3.2 nse 92.4±4.7 80.6±5.5 −12.8 ***
Panicle number (No./plant) 17.9±2.9 15.7±3.1 −12.6 * 18.7±3.5 13.8±2.8 −26.5 ***
aEach value for tiller number, dry mass, culm length and panicle number is the average of 40 plants and standard error (±S.E.). bThe percent change is based on the following relation: ((the value of sample−the value of control)/value of control)×100%. cTiller number was measured 8 weeks after transplantation.
dDry mass, culm length and panicle number were recorded at harvest. eNot significant (p>0.05).
fSignificance was estimated by the LSD test.∗p
<0.05,∗∗p<0.01 and∗∗∗p<0.001.
supplemental UV-B radiation was detected. Based on these results, an investigation was made of the effects of supplemental UV-B radiation filtered through cel-lulose diacetate film on the growth and yield of the two cultivars for 4 years (from 1994 to 1997). The
Table 3
Effects of supplemental ultraviolet-B irradiation on dry mass, culm length, panicle number and grain yield of two rice cultivars grown under lowland field conditions for four cropping seasonsa
Parameter Season Sasanishiki Norin 1
Control +UV-B Change (%)b pd Control +UV-B Change (%)b p
Dry mass (g/plant) 1994 52.1±1.3 51.2±1.4 −1.7 nse 44.1±1.1 42.2±1.4 −4.5 ns 1995 59.7±1.6 55.0±1.9 −7.8 * 47.6±1.0 45.6±1.1 −3.8 ns 1996 50.6±1.8 47.5±1.3 −6.0 ns 42.4±1.7 40.3±1.3 −4.6 ns 1997 58.2±1.6 55.5±1.8 −4.6 ns 51.9±1.7 54.5±1.5 +5.1 ns
Culm length (cm) 1994 96.6±0.3 96.6±0.6 +0.0 ns 94.8±0.5 96.8±0.5 +2.1 ** 1995 105.4±0.5 103.2±0.6 −2.1 ** 101.7±0.6 100.8±0.6 −0.9 ns 1996 78.7±0.7 80.1±0.5 +1.8 ns 83.5±0.6 83.4±0.4 −0.2 ns 1997 97.3±0.5 94.2±0.5 −3.3 *** 100.3±0.9 99.4±0.6 −0.9 ns
Panicle number (no./plant) 1994 13.8±0.3 13.1±0.4 −5.0 ns 14.4±0.5 13.3±0.3 −7.6 * 1995 15.3±0.4 14.0±0.4 −8.5 * 14.5±0.3 13.9±0.3 −4.1 ns 1996 13.7±0.4 13.6±0.4 −0.7 ns 13.4±0.6 13.5±0.4 +1.1 ns 1997 13.6±0.3 13.0±0.3 −4.6 ns 13.3±0.3 13.8±0.4 +4.4 ns
Grain yieldc(g/plant) 1994 28.7±1.0 27.4±1.6 −4.5 ns 22.2±1.2 21.5±1.0 −3.1 ns
1995 27.5±1.6 25.1±2.0 −8.7 ns 20.3±1.1 20.3±1.1 +0.0 ns 1996 26.6±1.4 25.1±0.3 −5.6 ns 22.9±0.8 21.3±0.7 −7.0 ns 1997 33.0±0.6 30.8±1.5 −6.7 ns 25.5±1.2 27.1±1.1 +6.3 ns
aEach value of dry mass, culm length, panicle number and grain yield is the average from 36 to 46 plants and standard error (±S.E.).
Percent change: 100−ratio (%) of plant height of sample/control.
bThe percent change is based on the following relation: ((the value of sample –the value of control)/value of control)×100%. cGrain yield is the rough weight of rice per plant.
dSignificance was estimated by the LSD test.∗p
<0.05,∗∗p<0.01 and∗∗∗p<0.001. eNot significant (p>0.05).
amount of supplemental UV-B radiation was adjusted to simulate a decrease in stratospheric ozone of about 20% (UV-BBE, 4.2 kJ/m2/day).
Fig. 1. Seasonal differences in tiller number during the tiller stage of Sasanishiki and Norin 1 grown under control conditions (open columns) and with supplemental UV-B treatment (shaded columns). Each value is the average of 36–46 plants and bars indicate standard errors. *, ** and *** indicate statistically significant differences between control plants and plants exposed to supplemental UV-B at
p<0.05, p<0.01 and p<0.001, according to the LSD test, respectively.
and panicle number recorded at final harvest varied seasonally. In the case of Sasanishiki, the dry mass, culm length and panicle number were significantly reduced by supplemental UV-B radiation in 1995. In 1997, the culm length of Sasanishiki was also reduced by supplemental UV-B radiation. For Norin 1, culm length was increased but panicle number was reduced
Table 4
Weight percentage of grains classified in terms of grain size for Sasanishiki and Norin 1 grown under control conditions and with supplemental UV-B treatmenta
Sasanishiki Norin 1
Grain size UV-B (%) Control (%) Grain size UV-B (%) Control (%)
1994 >1.9 mm 84.5 88.1 >1.8 mm 91.6 92.5
>2.0 mm 61.7 67.3 >1.9 mm 73.1 75.4
1995 >1.9 mm 79.6 81.8 >1.8 mm 89.7 90.4
>2.0 mm 54.9 64.3 >1.9 mm 68.1 71.4
1996 >1.9 mm 80.4 82.2 >1.8 mm 82.2 84.4
>2.0 mm 66.7 70.9 >1.9 mm 64.5 68.2
1997 >1.9 mm 83.0 86.7 >1.8 mm 89.4 89.3
>2.0 mm 65.6 71.3 >1.9 mm 78.2 79.3
aEach relative value (%) is the ratio of the grain weight for each grain size to the total grain weight for plants grown under control
conditions and with supplemental UV-B radiation.
tiller number in 1994, 1995 and 1997. In 1994 and 1995, Norin 1 exposed to supplemental UV-B radi-ation showed a significant reduction in tiller number during tillering. By contrast, in 1997, the tiller num-ber at 6 weeks after transplantation was significantly increased by supplemental UV-B radiation. In 1996, there were no great differences between tiller numbers in both cultivars grown with or without supplemental UV-B radiation.
Supplemental UV-B radiation reduced grain yields in both cultivars in 1994, 1995 and 1996 except in Norin 1 in 1997 (Table 3). Table 4 shows the relative distribution of weight percentages of grains classified in terms of grain size for the two cultivars grown under control conditions and with supplemental UV-B radi-ation. Fully ripened grains used for meals in Japan, are thicker than 1.9 mm for Sasanishiki or thicker than 1.8 mm for Norin 1. The weight percentage of fully ripened grains of controls of both cultivars varied sea-sonally, and decreased because of supplemental UV-B radiation in all seasons except in Norin 1 in 1997. It was thus confirmed that grains tended to be smaller with supplemental UV-B radiation in comparison with the controls and that the degree of decrease in grain size varied seasonally. This observation is commer-cially very important in Japan. The reduction in grain size might be due to a decrease in the photosynthetic activity of flag leaves due to the inhibition effects of supplemental UV-B radiation. It is further assumed that the reduction in grain size might result in a change
in grain protein content, which is very important for taste. This problem is now being examined.
There was no significant difference between two cultivars in their resistance to the effects of supple-mental UV-B radiation on growth and yield under field conditions, except in 1993. In previous experiments conducted in a phytotron (Kumagai and Sato, 1992; Hidema et al., 1996), Sasanishiki exhibited greater re-sistance to the inhibitory effects of UV-B radiation than Norin 1, and the stronger the UV-B radiation, the greater the difference in the reduction of growth between those two cultivars. This effect might be en-hanced by a high dose of UV-B radiation and unusual climate conditions such as less sunshine and lower temperature.
As described above, it was demonstrated the in-hibitory effects of UV-B radiation on growth and yield of rice cultivars under field conditions in a cool rice-growing region for the first time. These inhibitory effects of supplemental UV-B radiation might be markedly promoted by less sunshine and lower tem-perature during the cropping seasons. Multiple-year experiments under different climates and latitudes should be conducted in the future.
Acknowledgements
radia-tion system and Mr. Kunio Ichijyo for assisting in this research. The suggestions for improving the paper, provided by the anonymous reviewers, were much ap-preciated. This work was supported by Grants-in-Aid (nos. 10044195, 1076183 and 09NP0901) for Sci-entific Research from the Ministry of Education, Science and Culture, Japan, and the Second Toyota High-Tech Research Grant Program.
References
Blumthaler, M., Ambach, W., 1990. Indication of increasing solar ultraviolet-B radiation flux in alpine regions. Science 248, 206– 208.
Caldwell, M.M., 1971. Solar UV irradiation and the growth and development of higher plants. In: Giese, A.C. (Ed.), Photophysiology. Academic Press, New York, pp. 131–177. Dai, Q., Coronel, V.P., Vergara, B.S., Barnes, P.W., Quintos, A.T.,
1992. Ultraviolet-B radiation effects on growth and physiology of four rice cultivars. Crop Sci. 32, 1269–1274.
Dai, Q., Peng, S., Chavez, A., Miranda, M.L.L., Vergara, B.S., Olszyk, D.M., 1997. Supplemental ultraviolet-B radiation does not reduce growth or grain yield in rice. Agronomy J. 89, 793– 799.
Dai, Q., Peng, S., Chavez, A., Vergara, B., 1998. Effect of enhanced ultraviolet-B radiation on growth and production of rice under greenhouse and field conditions. In: Peng, S., Ingram, K.T., Neue, H.U., Ziska, L.H. (Eds.), Climate Change and Rice. Springer, Berlin, pp. 189–198.
He, J., Huang, L.K., Chow, W.S., Whitecross, M.I., Anderson, J.M., 1993. Effects of supplementary ultraviolet-b radiation on rice and pea plants. Aust. J. Plant Physiol. 20, 129–142.
Hidema, J., Kang, H.S., Kumagai, T., 1996. Differences in the sensitivity to UV-B radiation of two cultivars of rice (Oryza
sativa L.). Plant Cell Physiol. 37, 742–747.
JMA, 1998. Annual report of ozone layer monitoring: 1997. Japan Meteorological Agency, Tokyo.
Kim, H.Y., Kobayashi, K., Nouchi, I., Yoneyama, T., 1996. Enhanced UV-B radiation has little effect on growth, d13C
values and pigments of pot-grown rice (Oryza sativa) in the field. Physiol. Plant. 96, 1–5.
Kumagai, T., Sato, T., 1992. Inhibitory effects of increase in near-UV radiation on the growth of Japanese rice cultivars (Oryza sativa L.) in a phytotron and recovery by exposure to visible radiation. Jpn. J. Breeding 42, 545–552.
Madronich, S., McKenzie, R.L., Caldwell, M.M., Bjorn, L.O., 1995. Changes in ultraviolet radiation reaching the earth’s surface. Ambio 24, 143–152.
Rozema, J., Staaij, J., Bjorn, L., Caldwell, M., 1997. UV-B as an environmental factor in plant life: stress and regulation. Trends Ecol. Evol. 12, 22–28.
Sato, T., Kumagai, T., 1993. Cultivar differences in resistant to the inhibitory effects of near-UV radiation among Asian ecotype and Japanese lowland and upland cultivars of rice (Oryza sativa L.). Jpn. J. Breeding 43, 61–68.
Teramura, A.H., 1983. Effects of ultraviolet-B radiation on the growth and yield of crop plants. Physiol. Plant. 58, 415– 427.
Teramura, A.H., Sullivan, J.H., Lydon, J., 1990. Effects of UV-B radiation on soybean yield and seed quality: a 6-year field study. Physiol. Plant. 80, 5–11.
Teramura, A.H., Ziska, L.H., Sztein, A.E., 1991. Changes in growth and photosynthetic capacity of rice with increased UV-B radiation. Physiol. Plant. 83, 373–380.
