FIGURE 3 Effects of the drought treatment on the root metabolic costs of cotton. Statistical analysis of (A) phosphofructokinase, (B) malate dehydrogenase, (C) glucose-6-phosphate dehydrogenase, and (D) root respiration activities at 3 cm, 6 cm, 9 cm, and 12 cm segments from the taproot tips of the ”Guoxin 02” and ”Ji 228”. DT type, Drought-tolerant type ”Guoxin 02”; DS type, Drought-sensitive type ”Ji 228”; NS, no-stress; DS, drought stress; C, varieties; D, drought. Error bars represent standard errors of the means. P >0.05,P <0.05 and P <0.01 indicate no significance (ns), significant difference (*) and highly significant difference (**), respectively. Different lowercase letters in the figure indicate significant differences between different root segments under the same treatment (P ≤ 0.05).