Photosynthate transport rather than photosynthesis rate is critical for low potassium adaptation of two cotton genotypes

Figures & data

Table 1. Dry weights (g per plant) of different parts of genotypes 103 and 122 under different potassium treatments (K1 as low potassium treatment, 2 mg L⁻¹ KCl; K2 as control treatment 20 mg L⁻¹ KCl).

Tissue	103		122
	K1	K2	K1	K2
Root	0.38 ± 0.02b	0.50 ± 0.03a	0.28 ± 0.02c	0.58 ± 0.03a
Stem	0.44 ± 0.02c	1.09 ± 0.06b	0.37 ± 0.02c	1.48 ± 0.11a
Leaf	1.38 ± 0.02b	1.69 ± 0.12b	1.42 ± 0.09b	2.12 ± 0.15a
Leafstalk	0.18 ± 0.00c	0.29 ± 0.02b	0.14 ± 0.01c	0.36 ± 0.03a
Total	2.38 ± 0.04c	3.58 ± 0.23b	2.20 ± 0.13c	4.53 ± 0.26a

Note: Values are means of four replicates ±standard error. Plant parts with different letters are significantly different at P < .05 by LSD.

Figure 1. Dry mass decrease affected by low K treatment and K efficiency index of the two cotton genotypes. Values are means of four replicates ±standard error. * represent a significant difference at P < .05 by t-test.

Table 2. K concentration (%) of different parts of the two cotton genotypes under K1 (2 mg L⁻¹ KCl; low K treatment) and K2 (20 mg L⁻¹ KCl; control treatment) treatments.

Tissue	103		122
	K1	K2	K1	K2
Root	0.6 ± 0.05b	1.6 ± 0.05a	0.5 ± 0.02b	1.5 ± 0.19a
Stem	0.3 ± 0.03c	2.1 ± 0.11a	0.5 ± 0.05c	1.6 ± 0.12b
Leaf	0.5 ± 0.00c	1.5 ± 0.18a	0.4 ± 0.03c	1.0 ± 0.05b
Leafstalk	0.6 ± 0.06c	4.0 ± 0.21a	0.7 ± 0.06c	3.2 ± 0.23b

Note: Values are means of four replicates ±standard error. Plant parts with different letters are significantly different at P < .05 by LSD.

Table 3. K accumulation (mg per plant) of different parts of the two cotton genotypes under K1 (2 mg L⁻¹ KCl; low K treatment) and K2 (20 mg L⁻¹ KCl; control treatment) treatments.

Tissue	103		122
	K1	K2	K1	K2
Root	2.1 ± 0.1b	7.8 ± 0.5a	1.3 ± 0.1b	8.5 ± 0.7a
Stem	1.5 ± 0.1b	23.5 ± 1.6a	1.6 ± 0.2b	23.4 ± 1.2a
Leaf	7.1 ± 0.3b	24.9 ± 3.3a	6.2 ± 0.1b	22.0 ± 1.4a
Leafstalk	1.0 ± 0.2b	11.6 ± 1.2a	1.0 ± 0.1b	11.2 ± 0.9a
Total	11.7 ± 0.4b	67.8 ± 5.0a	10.2 ± 0.2b	65.2 ± 1.0a

Note: Values are means of four replicates ±standard error. Plant parts with different letters are significantly different at P < .05 by LSD.

Figure 2. Fractions (in percentages) of total plant potassium content in the (a) root, (b) stem, (c) leaf and (d) leafstalk of the two cotton genotypes under K1 (2 mg L⁻¹ KCl; low K treatment) and K2 (20 mg L⁻¹ KCl; control treatment) treatments. Values are means of four replicates ±standard error. Bars with different letters are significantly different at P < .05 by LSD.

Table 4. Effects of potassium on parameters of photosynthetic gas exchange in two different K efficiency cotton genotypes under K1 (2 mg L⁻¹ KCl; low K treatment) and K2 (20 mg L⁻¹ KCl; control treatment) treatments.

Treatment	NPn (μmol CO2 m^−2 s^−1)	GS (mol H2O m^−2 s^−1)	Ci (μmol CO2 mol^−1)	Tr (mmol H2O m^−2 s^−1)
103 K1	9.8c	0.16c	287.7bc	2.22c
122 K1	12.4b	0.28c	304.2ab	2.58c
103 K2	22.3a	0.44b	275.5c	4.45b
122 K2	24.1a	0.84a	316.3a	6.08a

Note: NPn is the net photosynthesis rate; GS is the stomatal conductance; Ci is the intercellular CO2 concentration; Tr is the transpiration rate. Values are means of four replicates ± standard error. Plant parts with different letters are significantly different at P < .05 by LSD.

Figure 3. (a) Starch, (b) soluble carbohydrate, (c) sucrose concentration and (d) ratio of root and leaf carbohydrate of the two cotton genotypes under K1 (2 mg L⁻¹ KCl; low K treatment) and K2 (20 mg L⁻¹ KCl; control treatment) treatments. Values are means of four replicates ±standard error. Bars with different letters are significantly different at P < .05 by LSD.