Table 4 Effect of growth regulators and thermal regimes on chlorophyll b contents and net photosynthetic rate-Pn (µ mol m−2 sec−1) in field conditions during 2012 and 2013.

From: Exogenously applied growth regulators protect the cotton crop from heat-induced injury by modulating plant defense mechanism

Thermal regimes

Regulators

Chlorophyll b 2012

Chlorophyll b 2013

Pn 2012

Pn 2013

 

Fiber fineness (micronaire) 2012

Fiber fineness (micronaire) 2013

Fiber length (mm) 2012

Fiber length (mm) 2013

Optimal regime

Control

0.58 a ± 0.045

0.57 a ± 0.043

20.5 ± 1.37 c

19.2 ± 1.22 c

April

4.0 b ± 0.20

3.4 b ± 3.0

22.5 b ± 2.1

22.1 b ± 2.0

H2O2 (30 ppm)

0.61 a ± 0.051

0.57 a ± 0.048

26.6 ± 1.63 a

24.6 ± 1.78 a

4.6 a ± 0.26

3.9 a ± 3.7

26.5 a ± 2.4

26.3 a ± 2.4

SA (70 ppm)

0.55 a ± 0.040

0.53 a ± 0.039

20.3 ± 1.20 c

18.6 ± 1.15 c

3.8 b ± 0.23

3.3 b ± 3.1

22.7 b ± 2.0

22.3 b ± 2.1

MLE (30 times diluted)

0.56 a ± 0.044

0.54 a ± 0.041

23.5 ± 1.35 b

21.5 ± 1.44 b

4.5 a ± 0.22

3.9 a ± 3.8

26.6 a ± 2.3

26.2 a ± 2.5

ASA (70 ppm)

0.55 a ± 0.039

0.52 a ± 0.037

23.6 ± 1.50 b

21.4 ± 1.35 b

4.6 a ± 0.24

3.9 a ± 3.6

25.4 a ± 2.2

25.5 a ± 2.3

Supra-optimal

Control

0.40 b ± 0.032

0.41 b ± 0.022

17.7 ± 1.01 c

25.5 ± 1.50 b

May

3.3 b ± 0.17

4.1 a ± 4.0

19.1 b ± 1.7

27.0 b ± 2.6

H2O2 (30 ppm)

0.52 a ± 0.038

0.53 a ± 0.033

24.1 ± 1.60 a

28.5 ± 1.85 a

3.8 a ± 0.26

4.2 a ± 4.1

23.6 a ± 2.3

28.1 a ± 2.7

SA (70 ppm)

0.36 b ± 0.026

0.35 b ± 0.024

17.4 ± 0.98 c

25.1 ± 1.60 b

3.2 b ± 0.17

4.3 a ± 4.2

19.5 b ± 1.8

27.3 a ± 2.5

MLE (30 times diluted)

0.48 a ± 0.035

0.50 a ± 0.048

20.8 ± 1.30 b

23.8 ± 1.45 b

3.7 a ± 0.23

4.1 a ± 3.9

24.5 a ± 2.2

27.2 a ± 2.4

ASA (70 ppm)

0.48 a ± 0.037

0.49 a ± 0.039

20.6 ± 1.26 b

23.5 ± 1.35 b

3.8 a ± 0.17

4.0 a ± 3.8

23.4 a ± 2.1

26.8 a ± 2.3

Sub-optimal

Control

0.51 a ± 0.043

0.55 a ± 0.045

28.2 ± 1.71 b

28.7 ± 1.80 b

June

4.0 a ± 0.18

4.2 a ± 4.2

26.1 a ± 2.5

27.5 a ± 2.6

H2O2 (30 ppm)

0.55 a ± 0.049

0.59 a ± 0.051

31.4 ± 2.01 a

32.0 ± 1.90 a

3.8 a ± 0.23

3.8 a ± 3.5

26.2 a ± 2.4

26.4 a ± 2.2

SA (70 ppm)

0.49 a ± 0.040

0.54 a ± 0.037

28.0 ± 1.55 b

28.0 ± 1.60 b

3.8 a ± 0.21

4.1 a ± 3.7

26.4 a ± 2.6

25.6 a ± 2.2

MLE (30 times diluted)

0.50 a ± 0.037

0.54 a ± 0.040

26.7 ± 1.42 b

26.9 ± 1.50 b

3.7 a ± 0.20

3.9 a ± 3.9

26.2 a ± 2.3

27.8 a ± 2.7

ASA (70 ppm)

0.47 a ± 0.035

0.52 ab ± 0.041

26.4 ± 1.47 b

27.1 ± 1.65 b

3.7 a ± 0.22

3.8 a ± 3.6

25.9 a ± 2.1

26.6 a ± 2.4

LSD

0.052

0.058

2.85

2.10

0.42

0.41

2.43

2.35

  1. Mean of three replications (n = 3) ± SE and variants having same alphabets are not statistically significant at P˂ 0.05. Main factors and interaction are significant at P˂ 0.01. By using the LSD of the interaction between growth regulators and thermal regimes, lettering is done separately for each thermal regime.
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