Studies on the pithiness of radish. II.

Abstract

The present studies was designed to elucidate the effect of naphthaleneacetic acid, sucrose and boric acid for preventing the occurrence of pithy tissue.It is necessary for us to avoid sun in order to produce the desired effect of NAA. The aqueous foliar spray solution contained NAA, sucrose and boron. separately and in combination, to give the final concentration of 50ppm, 2-5%, and 5ppm respectively. When the plants were sprayed with the solution containing boric acid and/or sucrose, the thickening growth of roots showed an increasing tendency, but the occurrence of pithy tissue could not be prevented. NAA was mainly effective in preventing the occurrence of pithy tissue. The treatment with these mixed solution for preventing the occurrence of pithy tissue and for decreasing the inhibition of the thickening growth in the root is recommended to be made after unfolding of four leaves.Foliar spray of NAA brought about the high percentage of pectic substances and a high degree of esterified pectin in the flesh tissue. This result supports the views that auxins are closely related to the esterification of pectic substances in the cell wall and act as senescence inhibitor to some extent.As the non-pithy tissue treated with NAA solution had a number of meristematic tissue on area basis in a cross section, the esterified pectin was high in content. This results supports the view that NAA is useful for delaying the process of maturation, and the main function of sucrose in feeding the phloem, and finally boron facilitates the transport of applied sucrose and NAA. The same experiment has been repeated every year and the same results has been obtained.