INFLUENCE OF PACLOBUTRAZOL IN THE SOIL ON GROWTH, NUTRIENT ELEMENTS IN THE LEAVES, AND FLOOD FREEZE TOLERANCE OF CITRUS ROOTSTOCK SEEDLINGS

Paclobutrazol yl)-4,4-dimethyl-2-(1,2,4-triazol-1-yl)pentan-3ol] was a pplied to soil at 0, 100, or 250 mg/3.78-liter pot containing seedling s of Swingle citrumelo, Carrizo citrange, Cleopatra mandarin, sour ora nge, rough lemon, and Sun Chu Sha. All cultivars were sensitive to pac lobutrazol, which caused a proliferation of shorter/thicker roots, and top growth showed shorter internodes and lower dry weight. Induced ch anges resulted in greater root/shoot ratios, and paclobutrazol treatme nts showed higher concentrations of nitrogen, calcium, boron, iron, an d manganese in the leaves of different cultivars. Paclobutrazol-treate d seedlings did not show a greater ability to tolerate flooded soil fo r 60 continuous days under greenhouse conditions nor survive -6.7 degr ees C controlled freeze tests. Paclobutrazol is a potentially useful p lant growth regulator to dwarf citrus, but it apparently is not a stro ng candidate for increasing flooding and freezing tolerance in citrus rootstock seedlings.