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Figure 7. The putative relationship between carbohydrates, cellulose, pigment, and phenylalanine ammonia lyase (PAL) activity. Carbohydrates are the substrate for both the synthesis of cellulose and pigments. Phenylalanine ammonia lyase plays an important role in the synthesis of flavonoids. In colored cotton fibers (CCFs), more active PAL activity results in higher flavonoid concentration. It remains unclear what signals regulate the activity of PAL in cotton fibers and what the complete reason is for that cellulose concentrations were much lower in CCFs and WCF. The solid line and arrows indicate the pathway to synthesize more pigment but less cellulose catalyzed by higher PAL activity in CCFs; the dash line and arrows indicate the pathway to synthesize much less pigment but more cellulose by lower PAL activity in WCF. The sketch is not a scale drawing.
