Effects of auxin and boron on nucleic acid metabolism and cell division during adventitious root regeneration

SUMMARY Treatment with indolebutyric acid (IBA) enhances root regeneration in stem cuttings of mung bean (Phaseolus aureus Roxb.) provided cuttings are supplied with borate. Treatment also increases the content of RNA in hypocotyls although RNA synthesis is inhibited by such treatment. Cell division in phloem parenchyma cells is evident 24 h after cuttings are prepared, irrespective of treatment with, or without, IBA. Following the preparation of cuttings, synthesis of RNA increases in the hypocotyl prior to the earliest mitoses in these cells and continues to increase in the presence of supplied borate. Autoradiographic investigation shows that, in the absence of supplied borate, synthesis of RNA within the nucleus decreases markedly in IBA‐treated cuttings 40 h after cuttings are made. Moreover, RNA synthesis is totally inhibited 24 h later whereas cell division does not cease until 60 h. Witholding supply of boron For up to 72 h after cuttings are made has no effect on DNA synthesis.