Table 4.

Effect of the number of applications of two growth regulators (cytokinins (CK) or brassinosteroids (BR)) on the crop stress index (CSI) and relative tolerance index (RTI) of rice plants of genotype Federarroz 2000 subjected to combined heat stress (40°C day/30°C night) at 88 days after emergence (DAE).

Treatments	CSI	RTI (%)
Absolute control	0.56 ab	——
Heat stress control	0.93 a	19.10 d
One spray of CK	0.32 b	36.20 cd
Two sprays of CK	0.40 ab	57.14 b
Three sprays of CK	0.38 ab	44.49 bc
One spray of BR	0.49 ab	27.66 cd
Two sprays of BR	0.51 ab	32.64 cd
Three sprays of BR	0.64 ab	77.31 a
Significance	*	***

The treatments evaluated were as follows: absolute control (AC), heat stress control (SC), one foliar spray of CK (CK1), two foliar sprays of CK (CK2), three foliar sprays of CK (CK3), one foliar spray of BR (BR1), two foliar sprays of BR (BR2) and three foliar sprays of BR (BR3). Data represent the mean of five data points ± standard error (n = 5). Data followed by different letters indicate statistically significant differences according to Tukey’s test (P ≤ 0.05). Equal letters indicate that the means are not statistically significant (≤0.05). NS, *, ** or *** not significant or significant at P ≤ 0.05, 0.01 or 0.001, respectively.