Effect of potassium on micromorphological and chemical composition of three cotton (Gossypium hirsutum L.) genotypes

An experiment was conducted at National Agricultural Research Centre (NARC), Islamabad, Pakistan to study the effect of potassium on yield and internal leaf tissues composition of cotton varieties, CIM-443, CIM-109 and CIM-446. Nitrogen (N) and phosphorus (P) were applied at 150 mg N/kg soil and 75 mg P 2 O 5 /kg soil to all the pots, while potassium (K) was applied at three levels; control (no K), 100 and 200 mg K 2 O/kg soil. It was observed that epidermal and mesophyl cells were more turgid, uniform, flaccid, symmetrical and structurally improved with potassium application. Larger number of starch grains was observed in plant leaves grown without potassium application while in leaves supplied with K their number decreased. Thickness of the epidermal region (cuticle plus epidermis) increased significantly with potassium application and same was true for leaf thickness in all the varieties. Application of K decreased N content of leaves significantly while protein content increased. Protein contents were maximum (65 μg/g) at 200 mg K 2 O/kg soil over that of control treatment. Phosphorus concentration also affected positively with potash application and it was maximum at 100 mg K 2 O/kg soil. An increase of 15.63% in leaf chlorophyll content was recorded with K at 200 mg K 2 O/kg soil. Seed cotton yield of all the varieties increased significantly with K application, maximum in case of CIM-446 followed by CIM- 109 and CIM-443 variety. A strong positive correlation was observed among applied K, leaf thickness, epidermis layer, chlorophyll contents, protein and seed cotton yield.