Abstract: The effects of the single and combined application of DPC(N, N-dimethyl perperidinium chloride)and KH₂PO₄ on the morphological characters and anatomical structure of the hypocotyl of cotton seedlings were studied under natural and shaded light condition (30-40% of natural light level).The results were as follows:the hypocotyl of the shaded cotton seedlings developed the poor tissue structure with small vascular bundles and fewer vessels, treatments of soaking cotton seeds with DPC, KH₂PO₄ and DPC+KH₂PO₄ solution respectively influenced the morphological characters and anatomical structures of hypocotyl among with the DPC+KH₂PO₄ treatment had the better effects.The synergism of DPC and KH₂PO₄showed that DPC+KH₂PO₄ treatment made the hypocotyl wider and shorter, and the hypocotyl possessed well developed vascular tissues, such as more vascular bundles and increased vessels and developed phloem and xylem. In the low light level owing to shading the effects were more significant than that in natrual lighting condition.

Key words: Plant growth regulator, Nutrient substance, Hypocotyl of cotton seedling, Anatomical structure