**2.7.1 Analysis on correlations between Tp and environmental factors**

Table 2 listed the correlations between Tp and weather or field environmental factors. It implied that Tp was regulated by various factors of canopy.


\* Sample no. 60, α0.05=0.259, α0.01=0.335.

Table 2. Correlations between plant temperature and weather or field environmental factors

### **2.7.2 Models of Tp at heights of 20 cm and 40 cm**

Four indices were chosen to establish models for Tp at heights of 20 cm and 40 cm in the present study: average temperature of inflow and outflow water [(Tin+Tout)/2], temperature margin between inflow water and air at 150 cm (Tin-TA), wind speed at 150 cm (V), and sunshine hours (S). Results showed that both of two equations showed significant high *R2* (equations 6 and 7 and Fig. 9). Among the five parameters, Tin and Tout can be obtained by an actual measure, and TA, V and S can be obtained from local weather station.

Fig. 9. Simulation effect of daily plant temperature at 20 cm and 40 cm heights.

Validation test showed that, the theoretical and practical values of Tp20 and Tp40 had significant correlations, and the slopes of the linear equation were 1.0183 and 0.9995, close to 1 (Fig. 9). The relative error [(∑︱practical-theoretical︱/practical)/*n*] of Tp20 and Tp40 were 3.93% and 2.95%, respectively.

Tp of 20 cm:

170 Agricultural Science

Table 2 listed the correlations between Tp and weather or field environmental factors. It

Tp20 1 0.997\*\* 0.985\*\* 0.990\*\* -0.360\*\* 0.944\*\* 0.973\*\* 0.981\*\* 0.260\*

Tp40 1 0.982\*\* 0.995\*\* -0.366\*\* 0.944\*\* 0.971\*\* 0.988\*\* 0.270\*

Ta20 1 0.973\*\* -0.392\*\* 0.941\*\* 0.971\*\* 0.971\*\* 0.320\*

Ta40 1 -0.359\*\* 0.950\*\* 0.975\*\* 0.994\*\* 0.296\*

Wind speed (V) 1 -0.330\* -0.372\*\* -0.390\*\* -0.200

TA 1 0.269\*

(S) <sup>1</sup>

Table 2. Correlations between plant temperature and weather or field environmental factors

Four indices were chosen to establish models for Tp at heights of 20 cm and 40 cm in the present study: average temperature of inflow and outflow water [(Tin+Tout)/2], temperature margin between inflow water and air at 150 cm (Tin-TA), wind speed at 150 cm (V), and sunshine hours (S). Results showed that both of two equations showed significant high *R2* (equations 6 and 7 and Fig. 9). Among the five parameters, Tin and Tout can be obtained by an actual measure, and TA, V and S can be obtained from local weather

1 0.977\*\* 0.943\*\* 0.362\*\*

1 0.967\*\* 0.316\*

150 cm Wind speed (V)

Inflow temperature (Tin)

Outflow temperature (Tout)

TA

Sunshine hours (S)

**2.7 Simulation model of rice Tp by environmental factors** 

implied that Tp was regulated by various factors of canopy.

Item Tp20 Tp40 Ta20 Ta40

150 cm

(Tin)

Inflow water temperature

Outflow water temperature (Tout)

Sunshine hours

station.

\* Sample no. 60, α0.05=0.259, α0.01=0.335.

**2.7.2 Models of Tp at heights of 20 cm and 40 cm** 

**2.7.1 Analysis on correlations between Tp and environmental factors** 

$$T\_{\overline{r}}20 = 0.964(T\_{in} + T\_{out}) / 2 - 0.803(T\_{in} - T\_A) \\ V + 0.085(12 - S) \quad R^2 = 0.993^{\*\*}, \\ n = 61 \qquad \text{(6)}$$

Tp of 40 cm:

$$T\_P u = 0.937 (T\_{in} + T\_{out}) / 2 - 0.595 (T\_{in} - T\_A) V + 0.063 (12 - S) \quad R^2 = 0.998^{\*\*}, \\ u = 15 \qquad \text{(7)}$$

#### **2.8 Function for rice plant temperature**

It could be traced root as early as 1960's when field microclimate regulated by irrigated water was researched. The detailed procedure, however, was not described until two-line hybrid rice was applied (Xiao *et al* 2000, Zhou *et al* 1993). The sterility of rice TGMS line was controlled by temperature. A credible alteration point in temperature was important not only for selection and identification of TGMS lines, but for monitoring sterility alteration, determining effective methods to keep sterility of such TGMS, and increasing seed production of two-line hybrid rice (Lu *et al* 2004, 2007). In the practice of past two decades, techniques commonly used temperatures from thermometer-screen which was located in a 25×25 m2 green plot and 150 cm height in local weather station (TA). The sensitive part of rice plant to temperature, however, was in its canopy (Lu *et al* 2004, 2007, Zou *et al* 2005). We have noticed that the sterility of rice TGMS lines was affected directly by Tp rather than TA. Therefore, it would be more accurate to monitor sterility of TGMS by using Tp in sensitive organs (Lu *et al* 2007). Tp was the final consequence of various environmental factors including air, water, soil, and the heat exchange among them. When attacked by low temperature during sensitive stage, how does the plant response, and how are agronomical methods used for safeguarding the sterility of rice TGMS? Such issues should be addressed by further studies. It will be too late to guarantee seed

Plant Temperature for Sterile Alteration of Rice 173

The temperature indices of sterile alteration must include two aspects as parameter of type and scale. The parameter type denoted the type of temperature (screen temperature of average or maximum or minimum one, otherwise as plant temperature of stem or leaf). The temperature scale will include the upper point (seed setting rate from zero increased to 0.5%), the optimum (show highest seed setting rate), and the lower point (seed setting rate returned to zero again) of temperature, which were considered as the three basic temperature points.

A lower thermo-sensitive genic male sterile line, Peiai64S, which was widely used in twoline hybrid rice breeding, was chosen as plant material. During the fertility-sensitive period of all treatments, the microclimate and plant temperature were regulated by irrigated water. Three irrigated depths of 5 cm, 10 cm, and 15 cm, each of these with flowing and staying-water were used. Flowing irrigated water of 15 cm depth was also treated. During the fertility sensitive stage, the stem temperature at plant height of 20 cm was measured continually per 10 s with an improved needle thermocouple sensor under various types of weather. At the fertility sensitive stage, the plant and panicle height were determined, and furthermore the distance between the last two leaves. For all the sowing date treatments, their self-fertilized seed setting rate was measured by 30 paper bag

The present chapter was aimed to establish such three basic temperature points.

**3.1 Temperature differences between rice field and screen of weather station** 

rature I II III IV

Screen 24.6±5.82 23.0 22.7 32.0

rature Difference Tempe-

150cm 23.91±5.82 0.69\*\* 22.89 0.11 22.32 0.38 31.05 0.95 100cm 23.50±6.80 1.10\*\* 22.79 0.21 22.21 0.49 30.79 1.21 60cm 23.77±5.94 0.83\*\* 22.86 0.14 22.33 0.37 30.68 1.32 40cm 23.42±5.88 1.18\*\* 22.69 0.31 22.18 0.52 30.21 1.79 20cm 22.97±5.29 1.63\*\* 22.46 0.54 22.25 0.45 29.44 2.56
