Minimum and maximum temperature (°C)
Minimum and maximum temperatures were recorded inside the polyhouse and ambient condition by using thermo-hygrometer from 18th DAS to maturity stage. It was observed that the mean minimum temperature (°C) recorded inside the polyhouse condition was 25.1°C and ambient condition was 24.1°C. Difference of mean minimum temperature was 1.0°C. The mean maximum temperature (°C) recorded inside the polyhouse condition was 40.8°C and ambient condition was 31.5°C. Difference of mean maximum temperature was 9.3°C. There are two extremes for this temperature, lower developmental threshold (base temperature) and upper developmental threshold. Below base temperature and above upper developmental threshold growth of the plant will stop
(Wahid et al., 2007). The optimum temperature for the normal development of rice ranges from 27 to 32°C
(Satake and Yoshida., 1978).
Anthesis time (am)
In the present study, anthesis time was early in plants sprayed with 4mM L-1 methyl jasmonate at 7am was 08:1 am whereas, for control anthesis time was 11:54 am (Table 1). These findings are in line up with the findings of
Zeng et al., (1999). They reported that methyl jasmonate induced rice florets opening within about 30 minutes of different rice cultivars.
Pollen viability (%)
In the present study, pollen viability was drastically reduced in control plants (37.52%) whereas, the considerable increase in plants sprayed with 4mM L
-1 methyl jasmonate at 7 am (61.93 %) and 2mM L
-1 methyl jasmonate at 7 am (58.64 %) (Table 1). These findings are supported by
Fahad et al., (2016). They reported that methyl jasmonate improves the pollen viability compared to the plants which were not treated under high temperature stress condition in rice. Early morning flowering character can be effectively used for the escape from the heat stress which induced the sterility of the spikelet during anthesis by shedding of the viable pollen while in the cooler hours in the morning on to the receptive stigma
(Satake and Yoshida, 1978).
Spikelet fertility percentage (%)
In the present study, the spikelet fertility percentage was increased in 4mM L
-1 methyl jasmonate at 7 am (56.07%) whereas, there was considerable reduction in spikelet fertility percentage in control (33.09%) (Table 1).
Fahad et al., (2016) reported that methyl jasmonate improved the spikelet fertility under high temperature stress condition in rice. MeJA (Methy Jasmonate) was a crucial cellular regulator involved in developmental process in several plants
(Norastehnia et al., 2007; Kim et al., 2009). Foliar application of MeJA brings alteration in various physiological processes and hence stimulates plant defense responses against abiotic and biotic stresses
(Walia et al., 2007). Clarke et al., (2009) reported that exogenous application of MeJA in
Arabidopsis thaliana improved basal thermo-tolerance and protected from the heat shock damage.
Grain yield per plant (g)
In the present study, grain yield per plant in 4mM L
-1 methyl jasmonate at 7 am was 8.55 g (Table 1). There was considerable reduction in grain yield per plant in control was 4.22 g. These findings are in line up with the findings of
Fahad et al., (2016) reported that methyl jasmonate improved the grain yield per plant under high temperature stress condition in rice. A significant impact of high temperature stress is mainly observed in tomatoes (
Lycopersicum esculentum) as it affects meiosis, fertilization and growth of fertilized embryos eventually leading to a significant decrease in yield and fruit quality
(Camejo et al., 2005; Amrutha and Beena, 2020; Vijayakumar et al., 2021) and lentil
(Baidya et al., 2020). Early morning flowering trait can be effectively used for the escape from the high temperature stress which helps to reduce the sterility of the spikelet during anthesis by shedding of the viable pollen while in the cooler hours in the morning on to the receptive stigma and which leads to significant increase in grain yield
(Satake and Yoshida, 1978).
1000 grain weight (g)
Application of 4mM L
-1 methyl jasmonate at 7 am recorded 1000 grain as 21.32 g. This treatment was at par with 2mM L
-1 methyl jasmonate at 7 am (21.02 g) and 4mM L
-1 methyl jasmonate at 8am (20.83g). There was reduction in 1000 grain weight in control as compared to treatments (Table 1). This result was supported by
Anjum et al., (2016). Early morning flowering trait leads to significant increase in grain yield and grain weight
(Satake and Yoshida, 1978).
