In vitro modification of spinach plasmalemma thickness

Floral induction in the long day plant spinach (Spinacia oleracea) has been shown to be accompanied by a thickening of plasmalemma. This change was observed at early evocation, in both shoot apices and leaves, as well as after inducing GA₃ treatment. To get further information on this thickening, plasma membranes from spinach leaves were isolated, in the present study, using aqueous two phase partitioning and the effect of variousin vitro treatments on their thickness was investigated. The average plasmalemma thickness was unaffected by Na⁺ and K⁺ ions. It was increased upon the effect of either Ca²⁺ or gibberellic acid. A thickening of plasmalemma was also observed when plasma membranes from vegetative plants were incubated with a cytosolic preparation from photoinduced plants. The results were discussed in relation with the plasmalemma modifications previously reported in spinach.