Anatomical and histochemical changes in germinating seeds of Pinus radiate treated with Tordon herbicides

Abstract

Tordon 22K (picloram) and Tordon 50D (1 part picloram + 4 parts 2,4-dichlorophenoxyacetic acid) did not affect the germination of Pinus radiata seeds, but seedlings developed flaccid cotyledons, reduced in length in some instances, and elongated and twisted in others. Hypocotyls and radicles were swollen and reduced in length.Cell vacuolation was extensive in treated embryos, and epicotyls appeared less conical compared with the controls, possibly as a result of reduced cell expansion and alterations in the normal plane of division. In the lower hypocotyls-root tissues, an area of proliferating small-diameter cells formed as a result of rapid and aberrant cell divisions and the failure of these cells to expand normally.Starch and lipid metabolism were reduced in treated tissues, especially in the small cell area. Protein bodies were present in all cells of the embryos and were apparently unaffected by herbicide treatment. RNA content appeared to be greater in cytoplasm of cells in the sheath of small cells and the nucleoli of cortical cell nuclei were enlarged, especially in tissues treated with Tordon 50D.It is suggested that both herbicides acted similarly to induce aberrations in the normal plane of cell division, possibly by altering nucleic acid metabolism.