Regulation of the Growth Processes in Pea (Pisum sativumL.) by Oxylipin (9Z)-12-hydroxy-9-dodecenic Acid

Abstract

Early in seed germination, tissue lipoxygenases are activated, and the genes encoding these enzymes are rapidly expressed [1]. This evidence indicates that lipoxygenases play a physiologically important role at the initial stages of development. Such a multifunctional profile [2] of lipoxygenases presumes that they participate in cell proliferation. To illustrate, jasmonates are involved in the synthesis of taxol, a microtubule-stabilizing agent, in plant cells [3, 4]. (9 Z )-12hydroxy-9-dodecenic acid (12-HDA) was shown to promote the growth of callus derived from young soybean epicotyl [5]. Young callus consists mostly of meristematic cells, and therefore we suggest that 12-HDA particularly promotes cell divisions. That is why we studied the effect of oxylipin on the mitotic activity of root meristem and other indices of growth activity in pea. The relative numbers of dividing cells were assessed in the root meristem of pea plants, cv. Tatarstan. To follow the effects of 12-HDA on cell division, the etiolated seedlings were transferred for 0.5, 1, 2, 4, and 5 h to 10 —9 and 10 —6 M oxylipin solutions. Roots were fixed and stained with acetic orcein, and cell numbers were counted under an NU 2/E microscope (Carl Zeiss, Germany) at 500 〈 magnification. To follow the growth function, seeds were germinated for three days in the same 12-HDA solutions. Amylases were extracted with NaCl solutions, and amylase activity (AA) was assayed by incubating the enzyme extract with starch solution and determining spectrophotometrically the nonnhydrolized starch residue [6]. The data on mitotic activity were processed using Student’s t test; in the case of the growth function and AA, the confidence intervals at p 05 were calculated on the basis of the standard errors.