JIA-2018-09

1995 ZHANG Xiang et al. Journal of Integrative Agriculture 2018, 17(9): 1991–1998 3.3. GPT activity in the cotton boll in response to DH/ NN stress treatments There was no significant difference in GPT activity after exposure to the temperature stress for 4 d. Compared with the control, the DH/NN stress treatment had a significant effect on the GPT activity in the boll after 7 d of exposure, causing a reduction in activity of 18.06 and 15.11% for SK-1 and SK-3, respectively (Table 2). After 10 d of exposure, the activity for the two cultivars was decreased by 42.4 and 36.8% for SK-1 and SK-3, respectively. The correlation analysis further showed that there was a positive correlation between GPT activity and Cry1Ac protein content in boll shell ( r =0.989 ** ). 3.4. The boll shell soluble protein content in response to DH/NN stress treatment The DH/NN stress treatment decreased the soluble protein in the boll shell (Table 3). There was no significant difference in soluble protein content on the 4th d under the stress. Compared with their corresponding controls, on the 7th d of treatment, the content of soluble protein was reduced by 24.1 and 17.7% for SK-1 and SK-3, respectively. On the 10th d under stress, the content in the two cultivars was decreased by 50.4 and 38.5%, respectively. The correlation analysis further showed that there was a positive correlation between the content of soluble protein and the Cry1Ac protein content in the boll shell ( r= 0.996 ** ). 3.5. Amino acid activity in the boll shell in response to DH/NN stress treatments The results showed that the stress of the DH/NN treatment significantly affected the contents of amino acids for the two cultivars (Table 4). Compared with the respective control, the DH/NN stress treatment increased the amino acid content in the boll shell on the 7th d by 36.3 and 18.6% for SK-1 and SK-3, respectively. After 10 d under the stress, the contents for the two cultivars increased by 90.3 and 59.3%, respectively. The correlation analysis further showed that there was a negative correlation between amino acid content and Cry1Ac protein content in the boll shell ( r =–0.924 ** ). 3.6. The boll shell protease activity in response to DH/NN stress treatments The stress of DH/NN significantly increased the protease activities in the boll shell (Table 5). On the 7th and 10th d, the activities for the treatments of SK-1 significantly Table 2 Effect of the 38/27°C day/night temperature regime stress on the glutamic pyruvic transaminase (GPT) activity in the boll shell of Bt cotton at boll stage (μmol g –1 FW h –1 ) in 2013 Stress time (d) SK-1 1) SK-3 1) Treatment CK1 Treatment CK2 0 11.2 a 11.2 a 13.1 a 13.2 a 4 10.8 a 11.2 a 13.1 a 13.1 a 7 9.6 b 11.7 a 11.3 b 13.4 a 10 6.7 c 11.7 a 8.3 c 13.2 a Significance ( P ) 0.031 0.911 0.024 0.924 1) CK1 and CK2 are the controls for Sikang 1 (SK-1, a conven­ tional cultivar) and Sikang 3 (SK-3, a hybrid cultivar). The values are means ( n =3). Means followed by the same letter are not significantly different according to LSD ( P =0.05). Table 3 Effect of the 38/27°C day/night temperature regime stress on the content of soluble protein in the boll shell of Bt cotton at boll stage (mg g –1 FW) in 2013 Stress time (d) SK-1 1) SK-3 1) Treatment CK1 Treatment CK2 0 3150 a 3150 a 3220 a 3220 a 4 3120 a 3140 a 3260 a 3270 a 7 2380 b 3130 a 2630 b 3200 a 10 1550 c 3130 a 1820 c 2960 a Significance ( P ) 0.031 0.982 0.024 0.953 1) CK1 and CK2 are the controls for Sikang 1 (SK-1, a conven­ tional cultivar) and Sikang 3 (SK-3, a hybrid cultivar). The values are means ( n =3). Means followed by the same letter are not significantly different according to LSD ( P =0.05). Table 4 Effect of the 38/27°C day/night temperature regime stress on the content of free amino acids in the boll shell of Bt cotton at boll stage (mg g –1 FW) in 2013 Stress time (d) SK-1 1) SK-3 1) Treatment CK1 Treatment CK2 0 155.9 c 155.9 a 157.2 c 157.2 a 4 158.3 c 154.3 a 164.9 c 158.1 a 7 217.8 b 159.8 a 202.6 b 170.8 a 10 299.5 a 157.4 a 280.2 a 176.0 a Significance ( P ) <0 .001 0.793 <0.001 0.810 1) CK1 and CK2 are the controls for Sikang 1 (SK-1, a conven­ tional cultivar) and Sikang 3 (SK-3, a hybrid cultivar). The values are means ( n =3). Means followed by the same letter are not significantly different according to LSD ( P =0.05). Table 5 Effect of the 38/27°C day/night temperature regime stress on the protease activity in the boll shell of Bt cotton at boll stage (mg pro g –1 FW h –1 ) in 2013 Stress time (d) SK-1 1) SK-3 1) Treatment CK1 Treatment CK2 0 2.9 c 2.9 a 3.6 c 3.6 a 4 2.9 c 2.9 a 3.6 c 3.5 a 7 4.2 b 2.9 a 4.5 b 3.6 a 10 5.7 a 2.9 a 6.4 a 3.6 a Significance ( P ) <0.001 0.924 <0.001 0.931 1) CK1 and CK2 are the controls for Sikang 1 (SK-1, a conven­ tional cultivar) and Sikang 3 (SK-3, a hybrid cultivar). The values are means ( n =3). Means followed by the same letter are not significantly different according to LSD ( P =0.05).