Physiological Aspects of Potassium Nutrition in Cotton

C.W. Bednarz, D.M. Oosterhuis, and D.L. Hendrix


The relationships between leaf, petiole, and root potassium (K+) concentration, leaf photosynthesis (Pn), and sugar content were studied using cotton (Gossypium hirsutum L.) in a growth chamber located at the Altheimer laboratory in Fayetteville, AR. The plants were grown hydroponically with full strength Hoagland's solution. At 35 days after planting the treatments were established consisting of (1) a continuation of full strength Hoagland's nutrient solution, and (2) a modified nutrient solution containing no K+. Measurements were initiated one day after treatment establishment and continued for two weeks. All leaf measurements were completed on leaves of known age at main-stem nodes 6 and 10. Root K+ and main-stem number 10 leaf K+ began to decline as soon as treatment 2 was established and continued to decline for the next two weeks. Leaf K+ at main stem node 6 remained constant for the first 7 days of the study and then began to decline. Leaf total glucose, fructose, and sucrose was extracted from leaf discs taken at 7:00 a.m. and 5:00 p.m. on each day. These soluble sugars were found to be higher when leaf K+ was depressed. Samples taken in the evening also contained more soluble sugars than those taken in the morning. Leaf Pn did not vary across K+ treatments. Leaf Pn at main-stem node 10 reached a maximum at a leaf age of approximately 10 days. Future studies will show specifically how carbohydrate translocation is depressed under a K+ limitation.

Reprinted from Proceedings of the 1994 Beltwide Cotton Conferences pg. 1330
©National Cotton Council, Memphis TN

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Document last modified Sunday, Dec 6 1998