Lipid Composition of Whole Roots and of Ca2+, Mg2+-activated Adenosine Triphosphatases from Wheat and Oat as Related to Mineral Nutrition

Lipid composition of whole roots of wheat (Triticum vulgare Vill. cv. Svenno Spring Wheat) and oat (Avena sativa L. cv. Brighton) and of cell wall fractions, mitochondrial fractions and microsomal fractions of these roots were studied. Lipid composition depended upon the level of mineral nutrition. In wheat total phospholipids, phosphatidyl choline and sulfolipid content was highest in the roots grown at the higher salt concentration, while the reverse was true for oat roots. In both species glycolipid and sterol content was lower in the high salt roots, at the same time as higher proportions of them were built into the microsomal fraction. Phosphatidyl choline content of the wheat root membrane fractions increased with the salt level, while the opposite occurred in the oat roots. The phosphatidyl choline content may be correlated with the (Ca²⁺, Mg²⁺)-stimulated ATPase activity.     

Effect of Evaporative Demand on Water Relations of Citrus limon

Conductance, transpirational flux and xylem pressure potentialwere measured in leaves of well-watered 5-year-old lemon trees(Citrus limon (L.) Burm. f.) subjected to different levels ofevaporative demand. Increased leaf-to-air absolute humiditydifference generally decreased stomatal conductance and increasedxylem pressure potential, with a good correlation between thelast two parameters; but this trend was reversed on days withvery high evaporative demand, when stomata opened in spite ofthe low humidity. Citrus limon (L.) Burm. f., lemon, water stress, stomatal conductance, leaf water potential, transpiration, air humidity