Effects Of Paclobutrazol (PP333) On Growth And Cadmium Uptake Of Two Hemp Cultivars

In order to explore the effects of the plant growth regulator on high biomass energy plant under cadmium stress, we use hemp which called Lu’an hemp and USO-31as experimental material to analysis the role of paclobutrazol (PP333) in two hemp cultivars under cadmium toxicity.In this experiment, solution culture experiment was carried out to study:The proper cadmium stress concentration on hemp seedlings; The optimal concentration of PP333treatment in alleviation cadmium toxicity on hemp seedlings; And the effects of300mg-L"1and400mg-L’1PP333treatment in50μmol L-1cadmium toxicity on hemp seedlings. The main results were as follows:the study demonstrated that treatment with different concentration of cadmium had obviously affected the growth indicators of hemp seedlings, such as increased the height of Lu’an hemp and USO-31and the biomass of Lu’an hemp under10μmol L-1Cd level. The absorption of plants to Cd enhanced with the increasing of Cd concentration, which mainly accumulated in root, with a plant dwarf, yellow blade and low biomass. No more than half biomass decreased of Lu’an hemp under50μmol L-1. Spaying with300mg L-1PP333had obviously increased the growth, the opposite for500mg L-1;400mg L-1PP333had significantly increased the total root length, root total volume, root number of USO-31and biomass of the two cultivars; alleviated the damage of photo synthetic pigments under Cd stress. Furthermore,300mg L-1and400mg L-1PP333also alleviated the membrane and root activities injury, decreased the content of soluble sugars and the Cd content of hemp. The anatomical structure index of leaves showed that single cadmium treatment increased the blade, lower epidermis, palisade tissue, spongy tissue thickness and the ratio of palisade tissue and spongy tissue (P/S).400mg L-1PP333had significantly restrained the changes in these indicators.The campus pollution-free soil (CK) and the complex heavy metals contaminated soil in Changsha were used to cultivate the two kinds of hemp, and the results showed that the growth of the hemp in Changsha soil was significantly inhibited, the plant height and biomass were significantly decreased (p<0.05). Complex heavy metals and separate paclobutrazol significantly reduced lignin content (p<0.05),600mg L-1PP333spraying to the hemp under heavy metal, the lignin content of Lu’an hemp and USO-31was58%,46%compare to the control.Exposed by the heavy metal treatment, the translocation factor (TF) of Zn, Cd, Cu, Pb of Lu’an hemp and USO-31was Cu>Pb>Cd>Zn and Cu>Cd>Zn>Pb, separately; the heavy metals mainly accumulated in the roots, and Cu has a higher translocation factor. PP333treatment significantly increased Zn content, decreased Cu, Pb, Cd content and their translocation factor. Spraying PP333to hemp enhanced the toxicity of heavy metals, possibly for antagonism or synergism between these heavy metals.