Preferential Growth of Haploid Plant Cells <Emphasis Type="Italic">in vitro</Emphasis>

HAPLOIDS from higher eukaryotes are of great importance for genetic analysis¹. The observation of Morpurgo² that haploid segregants can be obtained from diploid lines of Aspergillus nidulans by parafluorophenylalanine (PFP) treatment suggests that defined chemical manipulations may be useful in generating and maintaining haploid cells in cultures of higher plants. Parafluorophenylalanine has been found to induce haploidization not only in some species of Aspergillus, but also in some other genera of fungi such as Ustilago³.     

Some Biochemical Changes Associated with Paclobutrazol-Induced Adventitious Root Formation on Bean Hypocotyl Cuttings

Phaseolus vulgaris hypocotyl cuttings were placed in solutionscontaining either 0 (controls) or 43 µM paclobutrazolfor 24 h after which they were placed in peat– perlitefor 8 d. Paclobutrazol more than doubled the number of rootsformed on the cuttings but did not affect individual root length.Compared with controls, treated cuttings exhibited increasedactivities of catalase, peroxidase, polyphenol oxidase, malatedehydrogenase, protease and RNase in the base of the cuttings.These enhanced enzyme activities were particularly evident between3 and 5 d after excision. The largest paclobutrazol-inducedpromotion of enzyme activity occurred with malate dehydrogenasewhich was increased more than 2-fold compared with the controls.In contrast, paclobutrazol reduced amylase activity in comparisonto controls, suggesting that this enzyme may not be directlyrelated to root formation. These data indicate that the enhancementof adventitious root formation by paclobutrazol is accompaniedby changes in the activities of a number of enzymes which havepreviously been postulated to be involved in rooting. However,these changes in activity are generally greatest later in therooting period, suggesting that they may be involved in thedevelopment rather than the initiation of roots. Enzyme activity, growth regulator, Phaseolus vulgaris L., rooting