תפריט נגישות
ניגודיות עדינהניגודיות גבוהה
מונוכרום
הדגשת קישורים
חסימת אנימציה
פונט קריא
סגור
איפוס הגדרות נגישות
להורדת מודול נגישות חינם תפריט נגישותניגודיות עדינהניגודיות גבוההמונוכרוםהדגשת קישוריםחסימת אנימציהפונט קריאסגוראיפוס הגדרות נגישותלהורדת מודול נגישות חינםMagnesium deficiency of tomato (Lycopersicon esculentum Mill.) plants grown under glass and in the field is widespread. Deficiency may occur because of interference in Mg uptake by various cations or from diminishing rates of uptake resulting from root aging. To investigate the interrelationship of Ca and Mg uptake by tomato plants and the dependence of uptake on plant age, a solution culture study with various Mg and Ca concentrations (CMg, CCa) was conducted. From solution depletion measurements of Ca and Mg during 2 to 3‐day periods, net cation flux (Fmax) and Michaelis‐Menten uptake rate coefficients were estimated for various plant ages (18 to 21, 34 to 37, and 80 to 83 days) and solution composition. Enhanced CCa (2.5 vs. 1 meq/L) decreased Fmax and KM of Mg. This effect was attributed to stimulation by Ca of selective ion uptake (related to KM) and a competitive effect on carrier sites which reduced Fmax. Increased CMg values had no appreciable effect on Fmax of Ca but they enhanced KM, especially during early growth (18 to 21 days). The flux of Mg uptake decreased with plant age. Between Days 21 and 83, Fmax, was reduced from 68 to 17.5 µeq Mg g fresh root−1day−1, while KM values under the same conditions increased from 0.55 to 1.2 meq/L. Similar changes with time characterized the Fmax and KM values for Ca. Root and canopy growth rates were appreciably retarded at CMg of 0.05 or CCa of 0.1 meq/L, relative to those at higher Mg and Ca concentrations. At the initial appearance of deficiency symptoms, Mg and Ca concentrations in the shoots were 0.13 and 0.11%, respectively.
Magnesium deficiency of tomato (Lycopersicon esculentum Mill.) plants grown under glass and in the field is widespread. Deficiency may occur because of interference in Mg uptake by various cations or from diminishing rates of uptake resulting from root aging. To investigate the interrelationship of Ca and Mg uptake by tomato plants and the dependence of uptake on plant age, a solution culture study with various Mg and Ca concentrations (CMg, CCa) was conducted. From solution depletion measurements of Ca and Mg during 2 to 3‐day periods, net cation flux (Fmax) and Michaelis‐Menten uptake rate coefficients were estimated for various plant ages (18 to 21, 34 to 37, and 80 to 83 days) and solution composition. Enhanced CCa (2.5 vs. 1 meq/L) decreased Fmax and KM of Mg. This effect was attributed to stimulation by Ca of selective ion uptake (related to KM) and a competitive effect on carrier sites which reduced Fmax. Increased CMg values had no appreciable effect on Fmax of Ca but they enhanced KM, especially during early growth (18 to 21 days). The flux of Mg uptake decreased with plant age. Between Days 21 and 83, Fmax, was reduced from 68 to 17.5 µeq Mg g fresh root−1day−1, while KM values under the same conditions increased from 0.55 to 1.2 meq/L. Similar changes with time characterized the Fmax and KM values for Ca. Root and canopy growth rates were appreciably retarded at CMg of 0.05 or CCa of 0.1 meq/L, relative to those at higher Mg and Ca concentrations. At the initial appearance of deficiency symptoms, Mg and Ca concentrations in the shoots were 0.13 and 0.11%, respectively.
