THE INFLUENCE OF GROWTH PARAMETERS AND CLIMATIC ACTORS ON EFFICIENCIES OF SOLAR ENERGY UTILIZATION IN SUGARCANE ABSTRACT

Transcription

1 Plant Physioiogy THE NFLUENCE OF GROWTH PARAMETERS AND CLMATC ACTORS ON EFFCENCES OF SOLAR ENERGY UTLZATON N SUGARCANE Masaki Shimabuku, Masaaki Kudo and Koishi Tamaki Okinawa Agricultural Experiment Station, Naha 903 Japan ABSTRACT Field experiment was carried to find out the efficiency of solar energy utilization in relation to growth parameters and climatic factors, using seven sugarcane varieties with different plant types. The average values of each variety of the efficiency of solar energy utilization during the whole measuring period ranged from 1.1 5% to 1.70% with the average at 1.44%. The highest value of the efficiency of solar energy utilization in measuring period was 4.14 percent for F 160 variety. The efficiency of solar energy utilization was positively correlated (r = ** 1 with solar radiation. t was considered that the efficiency of solar energy utilization was mainly affected by the magnitude of leaf area index in the early period of rapid growth, by net assimilation rate in the later period of rapid growth, and by the intensity of solar radiation in both growth periods. Different values of leaf area index corresponding to the maximum values of the efficiency of solar energy utilization were observed in varieties. NTRODUCTON Solar radiation is the source of energy that is necessary for the dry matter production of all plants on earth. t is considered that the high productivity of crops is achieved by the improvement of the efficiency of solar-energy utilization in growth processes of crop population. There are a few studies about the efficiency of solar energy utilization in sugarcane. Komutsu Ogawa and Makino obtained about 1% efficiency of solar energy utilization using POJ 2878 in 1933, in Taiwan. The objectives of this paper are to know the change with timeof theefficiency of energy utilization in sugarcane varieties, and the efficiency of solar energy utilization in relation to growth parameters and climatic factors. 526

2 MATERALS AND METHODS The seven varieties with different plant types were planted oh September 9, 1976 in an experimental field of the Okinawa Agricyltural Experiment Station. Varieties used were NCo310, NCo376, F 160, F 161, RK65-368, RK65-37, and RK67-1. Sugarcane plants weregrownona fertile soil by applying standard cultural practices. All varieties received adequate fertilizer (3.75kg N, 1.87kg P205, 1.87kg K20 per 100m2). All varieties with one bud cutting (rayungan) were planted with a density of 1.25m x 0.2m. Determination of the dry weight of various parts of the sugarcane plant and leaf area were made at intervals of about one month. During the growth process, samples of the stools were taken at random. The first sampling started at about two months after planting. After determination of fresh weight of various parts, the same were dried in an oven at 80'~ for ~ ~ three days. Area of leaf blade excluding the area of leaf sheaths was measured by automatic area meter. The area of spindle leaves was also calculated from specific leaf area (SLA) of each variety. One sugarcane stool which had approximated the mean values of plant height, number of tillers, etc., to respective variety was sampled for the determination of top dry weight and leaf area. For five stooi materials, the roots were collected from soil consisting of the 0.625m3 volume (1.25m x m x 0.5m depth) and the dry weight was measured. Climatic data obtained at an Okimawa Meteorological Observatory that is located five kilometers away from the experimental field were used. The final harvest bf all varieties were made on February 1, 1978, sixty sugarcane stools were taken from a randomized block design of 6 replications. R ESU LTS The ratio of solar energy converted by a plant population as chemical energy to total incident solar energy is called "Lindeman Ratio." Change with time of the efficiency of solar energy utilization of sugarcane varieties are presented in Table 1. The equation used in the calculation of the efficiency of solar energy utilization is as follows: where H is combustion heat per one gram of dry matter (4 kcal), A W is the weight of dry matter increased in the period from Tn totn + 1 (g/m2), ZS is total incident short wave radiation energy (kcal/m2). The value of the efficiency of solar energy utilization during the whole

3 528 PLANT PHYSOLOGY measuring period ranged from 1. 5 sto 1.70%, giving 1.44% as average and 4.14% as the highest value. Change with time in the efficiency of solar energy utilization increased very rapidly during the period from February of 1977 to May,1977 and reached the highest value at late May, followed by rapid decrease. Correlation coefficient between efficiency of solar energy utilization and the four climatic factors are shown in Table 2. The efficiency of solar energy utilization was positively (r=0.7617"*) correlated with solar radiation though it was not significantly correlated with other three climatic factors. Table 3 shows correlation coefficients between the efficiency of solar energy utilization and growth parameters calculated from average value of seven varieties. The efficiency of solar energy utilization was positively correlated with leaf area index (r=0.7119"), and also crop growth rate (r=0.9917*). However, no significant correlation coefficient between the efficiency of solar energy utilization and net assimilation rate and relative growth rate was established. TABLE 1. Change with time in the efficiencies of solar energy utilization (Eu) in sugarcane varieties. Measuring Eu (%) of varieties. Mean Mean RK RK RK Period NC0310 NC0376 F160 F161 value LA Nov. 9-Nov Nov. 25-Dee Jan. 13-Feb. 3 Feb. 4-Mar. 8 Mar. 9-Apr. 12 Apr. 13-May 9 May 10-June. 9 Jun. 10-Jut. 17 Jul. 18-Aug. 29 Aug. 30-Oct. 3 Mean value of Eu (%) n order to know in detail the relation between the efficiency of solar energy utilization and growth parameters, correlation coefficients between the efficiency of solar energy utilization and growth parameters among varieties in the every measuring period are presented in Table 4. The efficiency of solar energy utilization was positively perfectly correlated with crop growth rate in almost all ofseasons. The efficiency of solar energy - utilization was positively (r=0.9368*", ")

4 TABLE 2. Correlation coefficients between the efficiencies of solarerlergy utilization and climatic factors. Mean daily Average, Daily Characters dally sunshine solar temperature hours ralnfall radhtlon SEu: -. efficiencies of solar energy utilization from dry matter of stalks TABLE 3. Correlation coefficients between the efficiencies of solar energy utilization and growth parameters. Leaf Crop Net Relative Characters area growth assimilation growth 'ndex rate rate rate Efficiencies of solar energy * * uitllzation correlated with leaf area index in the early period of rapid growth. When leaf area of sugarcane plant population kept larger LA, the efficiency of solar energy utilization was positively correlated with net assimilation rate (NAR). n both early and later periods of growth, the efficiency of solar energy utilization correlated with relative growth rate. Correlation coefficient matrix among maximum Eu, and mean Eu, optimum LA1 and maximum LA1 in the varieties was presented in Table 5. Maximum Eu was positively correlated with optimum LA1 (r=d84.97*), with maximum NAR (r= *), and also with maximum LA1 (r=0.8903**) in the varieties. Optimum LA1 was positively (r=0.7896*) correlated with maximum LA. Also, maximum NAR was positively (r=0.7293"-~.) correlated with maximum LA, but it was statistically significant. Table 6 shows the efficiency of solar energy utilization for dry matter of stalks that was related to economic yield. The efficiency of solar energy utilization for dry matter of stalks was 0.99%ontheaverage.Asshown in Table 2, the efficiency of solar energy utilization for dry matter of stalks was positively correlated with mean temperature (r=0.7365'), and with solar radiation (r=0.7304*). As described above, leaf area index seemed to be the most important factor responsible for the variation of the efficiency of solar energy utilization during the early period of rapid growth in the varieties. As shown in Fig. 1, an average regression curve between the efficiency of solar energy utilization and leaf area index could be drawn till leaf area index reached the highest value. Difference among varieties was observed in the value of LA1 corresponding to the maximum values

5 530 PLANT PHYSOLOGY TABLE 4. Correlation coefficients between the efficiencies of solar energy utilization and growth parameters in sugarcane varieties, Efficiencies Efficiencies Efficiencies Measuring of solar of solar of solar energy energy energy Perlod utilization utilization utilization and leaf and crop and net area index growth rate assimilation rate Efficiencies of solar 9nergy utilizatlon and relative growth rate 1976 Nov. 9-Nov ** NOV. 25-D~c * ** ** 1977 DeC. 13-Jan ** * 1977 Jan. 13-Feb * * ** ** 'Feb. 4-Mar ** * Mar. 9-Apr ** ** Apr. 13-May * ** ' May. 10-Jun * * * Jun. 10-Jul ** % * Jul. 18-AUg L.0000** ** Aug Ct O.b999** ** ** TABLE 5. Correlation coefficient matrix between maximum Eu (1) and mean Eu (21, optimum LA(31, maximum NAR (41, maximum LA(5) in - sugarcane varieties. Characters Medn Optlmum Maximum Maxlmum EU LA1 NA R LA Maximum Eu * ' ** Mean Eu Optimum LA ' Maximum NAR 0,7293 () : Maximum of efficiencies of solar energy utillzation (2) Mean of efficiencies of solar energy utilization. (31 : Optimum of leaf area ndex. (4) : Maximum of net assimilatlon rate. f5) Maximum of leaf area index. of the efficiency of solar energy utilization. DSCUSSON The highest value (4.14%) of the efficiency of solar energy utilization in this study was considerably higher than those reported earlier on other crop species, e.g., 30% in sudangrass (Loornis and Williams, and 2.9% in maize (Williams eta14). Also, this value was considerably higher than the highest value (3.32%) of rice

6 M. SHMABUKU ET AC 53 1 reported in "Maximal Growth Rate Experiments ( )" by Japanese Committee for the international Biological Program (JBP)~. However this value was lower than those reported on other crop species, e.g., 4.36% in soybean, 4.63% in maize, 4.52% in sugar beet in JBP~. * Mean value of 1.44% of the efficiency of solar energy utilization in this study was higher than those reported on crop species in JBP, e.g., 1.25% for lowland rice, 0.72% for soybean, 1.34% for maize, and 1.35% for sugar beet, which were average values for replication of five years. As shown in Table 2, it was considered that the efficiency of solar energy utilization was mainly affected by the intensity of solar radiation than the photoperiod because sugarcane belonged to C4 plant. t was reported by Hesketh and that the photosynthesis of sugarcane was enhanced by a strong radiation. MOSS' TABLE 6. Change with time in the efficiencies of solar energy utilizat~on for dry matter of stalks (SEu) of sugarcane varieties. Periods of SEU (%) of varieties Mean measurement RK. RK RK value NCo310 NCo376 F160 F161 Jan. 13-Feb. 3 Feb. 4-Mar. 8 Mar. 9-Apr. 12 Apr. 13-May. 9 May. 10-Jun. 9 Jun. 10-Jul. 17 Jut. 18-Aug. 29 Aug ct. 3 Mean value of SEu (96) p t was shown that the importaqce of leaf area index and net assimilation rate of sugdrcane population for the efficiency of solar energy utilization would change with growth period. The efficiency of solar energy utilization was more dependent on the'difference in the magnitude of leaf area index than net assimilation rate in the early period of rapid growth, but the influence of leaf area index for the efficiency of solar energy utilization was weakened in theperiod having larger leaf area index. On the other hand, the efficiency of solar energy utilization was mainly affected in the period having larger leaf avea index by the magnitude of net assimilation rate than leaf area index. Positive correlation, alth$ough not statistically significant, between maximum net assimilation rate and maximum leaf area index may suggest possibility of selection of varieties with higher net assim and larger leaf area index.

7 PLANT PHYSOLOGY RK65-37 " RK A NCo310 V Nco 376 v * a 0 Leaf area index (LA) FGURE 1. Relationship between LA1 and Eu in sugarcane varieties. The regression line is for the maximum LA. CONCLUSON. Relationship between the efficiency of solar energy utilization and growth parameters, and climatic factor were studied in an experimental field of Okinawa Agricultural Experiment Station. Change with time of the efficiency of solar energy utilization were drawn as a parabolic curve with the average value of 1.44%. 1 n an analysis on relationshi0 between the efficiency of solar energy utilization and growth parameters, a close positive correlati6n coefficient between the efficiency of solar energy utilization and leaf area index in the early period of rapid growth and a close positive correlation coefficient between the efficiency of solar energy utilization and net assimilation rate in the later period of rapid growth were found. The efficiency of solar energy utilization was positively.(r = **) correlated With solar radiation. Difference in sugarcane varieties was found in the Eu-LA1 curves which had leaf area index corresponding to maximum value of the efficiency of solar energy utilization. REFERENCES 1. Hesketh, John D. and Dale M. Moss (1963). Variation in the response of

8 photosynthesis to light crop science 3: Kanda M. (1975). Efficiency for solar energy utilization. crop Productivity and solar energy utilization in various climates in Japan. Murata, Y Loomis, R. S. and W. A. Williams (1963). Maximum crop productiyity:an estimate. Crop Science. 3: Williams, W. A., R. 5. Loomis and C. R. Lepley (1965), Vegetative growth of corn as affected by population density. Productivity in relation to interception of solar radiation. Crop Science 5: LA NFLUENCA DE PARAMETROS DE CRECMENTO Y FACTORES CLWATCOS SOBRE EFCENCAS DE JTLZACON DE ENERGA SOLAR EN VAREDADES DE CARA DE AZUCAR Masaki Shimabuku, Masaaki Kudo and Koichi Tamaki RESUMEN Se Uevaron a cab0 experimentos de campo para determinar la eficiencia de utilizacion de energia solar en relacion a parametros de crecimiento y factores clirnaticos, utilizando siete diferentes variedades de caiia de azucar. La eficiencia de utilizacion de energia solar durante todo el periodo de medicion oscilb desde 1.15 por ciento hasta 1.70 por ciento, con promedio de 1.44 por ciento., El valor mas alto de eficiencia de utilizacion de energia solar durante el periodo de medicion fue 4.14 por ciento para la variedad F 160. La eficiencia de utilizacion de energia solar estuvo correlacionada positivamente (r=0.7617**) con radiacion solar. Se consider0 que la eficiencia de utilizacion de energia solar fue principalrnente afectada por la magnitud del indiqe del area foliar durante el periodo inicial de rapido crecimiento, y por~similacio neta en el ultimo periodo de crecimiento, y por la intensiddd'de radiacion solar qurante ambos periodos de crecimiento. Se observaron diferentes valores de indica de area foliar correspondientes a valores maximos de utilizacion de energia solar.