Effect of External Nitrogen and Potassium Supply on Xylem Sap Composition of Sugarcane

Abstract

This study was conducted to evaluate the effect of nitrogen (N) and potassium (K) availability on root exudate composition of two sugarcane cultivars known to differ with regard to their resistance to drought and salinity stress. The plants were hydroponically grown in a greenhouse and subjected to three levels of N (0.1, 1.0, and 10 mM N) and three levels of K (0.02, 0.2, and 2 mM K). Nitrogen and K stress altered the xylem sap composition. Nitrogen stress significantly reduced nitrate (NO − 3 ), ammonium (NH + 4 ), calcium (Ca), magnesium (Mg), and amino acid content and increased the pH, phosphorus (P), and K content. Whereas, K stress significantly decreased pH, K, NH + 4 , and amino acid content but increased Ca, Mg, and P content. Nitrogen and K stress had opposing effects on xylem sap pH and osmolality. Results indicated that sugarcane plants recycle compounds between the phloem and xylem. The results also suggested that the NO − 3 and K concentration of xylem sap could be effectively used to estimate the N and K status of the soil solution.

Yield Component Differences between Direct-Seeded and Transplanted Super Hybrid Rice

“…Furthermore, sugar and amino acid concentrations in bleeding sap were 17% and 23% lower, respectively, in DS plants than in TP plants. Subasinghe (2007) stated that the chemical composition of bleeding sap could reveal useful information on the storage, mobilization, and movement of nutrients in plants and thus it could be used as an indicator of nutritional status in a number of plant species. In the present study, nitrogen, phosphorus and potassium contents of both leaves and stems were lower in DS plants than in TP plants, and the differences were significant in the nitrogen content in leaves as well as the potassium contents in both stems and leaves (Table 6).…”

Ion uptake and structural modifications induced by nitrogen source in tomato (Solanum lycopersicum Mill. Cv. Ibiza F1)

“…À were increased even in plants supplied with NO 3 À compared to NO 2 À (Tables 1 and 2). The results also suggested that the NO 3 À and K + concentration of xylem sap could be effectively used to estimate the N status of the soil solution [33]. It is not surprising that increased nitrate influx is associated with enhanced K + transporter expression because it has been previously documented that stimulated nitrate provision and uptake is associated with increased K + influx, which has an important and specific role in all living cells and functions as the major charge-balancing cation [34].…”

Efeito da inoculação de uma bactéria endofítica fixadora de nitrogênio (Acinetobacter sp. ICB117) no desenvolvimento da cana-de-açucar (Saccharum sp. variedade SP791011).

“…A No trabalho de Subasinghe (2007), não há relato de glutamina e asparagina como principais aminoácidos na seiva xilemática de duas variedades de cana-de-açúcar, mas sim outros aminoácidos, dentre eles está a arginina, porém não em maior porcentagem. Na referida pesquisa, a coleta da seiva foi realizada aos 4 meses de idade da planta e no início da experimentação o autor procurou diminuir o tamanho do tolete, para diminuir a reserva de nutrientes.…”

“…Diferente dessa afirmação, Biggs (2003) encontrou predomínio de asparagina na seiva xilemática de cana-de-açúcar. Subasinghe (2007) encontrou serina, alanina, lisina, arginina, valina e treolina na seiva xilemática de duas linhagens de cana-de-açúcar como principais aminoácidos constituintes, e em menor concentração ácido aspártico e ácido glutâmico.…”