Potassium concentration effect on growth, gas exchange and mineral accumulation in potatoes.
This study was conducted to evaluate the responses of potatoes to six K solution concentrations maintained with a flow-through nutrient film system.  Potato plants were grown for 42 days in sloping shallow trays containing a 1 cm layer of quartz gravel with a continuous flow of 4 ml min-1 of nutrient solutions having K concentrations of 0.10, 0.55, 1.59, 3.16, 6.44, 9.77 meq L-1.  Plant leaf area, total and tuber dry weights were reduced over 25% at 0.10 meq L-1 of K and over 17% at 9.77 meq L-1 of K compared to concentrations of 0.55, 1.59, 3.16 and 6.44 meq L-1 of K.  Gas exchange measurements on leaflets in situ after 39 days of growth demonstrated no significant differences among different K treatments in CO2 assimilation rate, stomatal conductance, intercellular CO2 concentration, and transpiration.  Further measurements made only on plants grown at 0.10, 1.59, 6.44 meq L-1 of K showed similar responses of CO2 assimilation rate to different intercellular CO2 concentrations.  This suggested that the photosynthetic systems were not affected by different K nutrition.  The leaves of plants accumulated about 60% less K at 0.10 meq L-1 of K than at higher K concentrations.  However, Ca and Mg levels in the leaves were higher at 0.10 meq L-1 of K than at higher K concentrations.  This indicates that low K nutrition not only reduced plant growth, but also affected nutrient balance between major cations.
Cao
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Department of Horticulture, University of Wisconsin, Madison 53706, USA.
Tibbitts
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TW
D002118:Calcium / Q000378:metabolism; D002245:Carbon Dioxide / Q000378:metabolism*; D018504:Ecological Systems, Closed; D005308:Fertilizers; D018527:Hydroponics / Q000379:methods; D008274:Magnesium / Q000378:metabolism; D009751:Nutritional Requirements; D018515:Plant Leaves / Q000254:growth & development / Q000378:metabolism; D011188:Potassium / Q000378:metabolism*; D011198:Solanum tuberosum / Q000254:growth & development* / Q000378:metabolism*; D013455:Sulfur / Q000378:metabolism
D005308:Fertilizers; D002245:Carbon Dioxide; D013455:Sulfur; D008274:Magnesium; D011188:Potassium; D002118:Calcium