Studies on Performance and Mechanism of Negative Phototropism of Chlorophytum comosum Roots and Its Regulation Effects of cytokinin on the growth and negative phototropism of Chlorophytum comosum var.variegata root Studies on Performance and Mechanism of Negative Phototropism of Chlorophytum comosum Roots and Its Regulation Impact of IAA, GA3, and ABA on Negative Root Phototropism and Root Growth of Rice