Influence of Nutrient Supply on Growth, Mineral Nutrients and Carbohydrates in Cucumber (Cucumis sativus L.)

We investigated the growth of cucumber plants, the uptake and use of mineral nutrients, such as NO₃?N, NH₄?N, K?, Ca??, Mg?? and Na?, absorbed from media solution, and the synthesis and distribution of soluble sugars under nutrient-deficient condition. Difference in plant growth revealed after 20 days of treatment. Nitrate uptake in nutrient-deficient condition was significantly reduced compared with nutrient-normal treatment, and its distribution was primarily in petioles, stem, roots and less inleaves. In contrast, ammonium content was markedly predominated in fast growing organs, and it was significantly different in growing leaves, expanded leaves, and roots under similar growth conditions. K?, lack by deficient nutrient condition, was found in growing leaves. The Ca?? content did not show significant difference between treatments and a substantial portion of Ca?? remained in petioles. The Mg?? content was significantly higher in the leaves of nutrient-normal condition compared with nutrient-deficient condition while significantlylower in stem and roots. The behavior of Na? in plant was similar to K? although its content was relatively little. The highest CO₂ assimilation was observed in fully expanded leaves of nutrient-normal condition, which was 1.7 times higher compared with nutrient-deficient condition. The instantaneous water use efficiency (A/E) and the A/gsratio, which is an index of leaf intrinsic water use efficiency for individual leaves, was 1.2 and 1.1 times higher, respectively. The total soluble sugar (TSS) contents were highest in leaves followed by petioles, stems and roots, and in younger leaves. The growing leaves contained about 7,200 ㎎ ㎏?¹ of TSS in nutrient-normal condition whereas the TSS contents in nutrient-deficient condition were not significantly different between leaves. The Mg?? and NH₄? N were positively correlated with the TSS whereas NO₃? N was negatively correlated.