**4. Conclusion**

262 Solar Radiation

cultivar effect was not observed. The standardized partial regression coefficient for air temperature was 1.580; on the other hand, the standardized partial regression coefficient for solar radiation was small (0.180). The multiple correlation coefficient determined by the general linear model for panicle temperature was 0.891 (*p* < 0.001), and three weather factors (air temperature, solar radiation, and vapor-pressure deficit) also significantly influenced on panicle temperature (Table 7). A cultivar effect was not detected. The standardized partial regression coefficient for air temperature was 1.430; on the other hand, the standardized partial regression coefficient for solar radiation (0.225) was slightly larger than that of the

Cultivar Air

Leaf temperature 0.911\*\*\* 0.42 ns 84.91\*\*\* 6.96\* 11.30\*\* 2.92 ns

Panicle temperature 0.891\*\*\* 1.21 ns 85.21\*\*\* 13.32\* 10.82\* 0.06 ns

Leaf temperature 1.580 0.180 −0.702 −0.072

Panicle temperature 1.430 0.225 −0.620 −0.010

Table 7. Results of multiple regression analysis using general linear models for the correlations between four weather factors (air temperature, solar radiation, vapor-pressure deficit, and wind speed) and panicle and leaf temperatures for every hour during 0600 and 1200.

The direct effects of solar radiation on panicle and leaf temperatures were smaller than those of air temperature and vapor-pressure deficit because the standardized partial regression coefficient for air temperature was much larger than that for solar radiation (Table 7.). Higher solar radiation on August 13 resulted in higher panicle and leaf temperatures (Fig. 10.), but air temperature was also affected by solar radiation; higher air temperature also resulted in higher panicle and leaf temperatures. Yoshimoto et al. (2007) estimated the panicle temperature in New South Wales, Australia and in Jiangsu Province, China, using

ns (not significant). \*, \*\*, and \*\*\* (significant at *p* < 0.05, *p* < 0.01, and *p* < 0.001) respectively.

Solar radiation

temperature

Standardized partial regression coefficient

*F* values in the generalized linear models

Solar radiation

Vapor-pressure deficit

Vaporpressure deficit

Wind speed

Wind speed

generalized linear model for leaf temperature.

Multiple correlation coefficient

> Air temperature

Dependent variables

Dependent variables

**3.3 Discussion** 

