Huong DongHuong dong cua thuc vat la mot hinh thuc phan ung cua mot bo phan cua cay doi voi cac tac nhan kich thich theo mot xu huong xac dinh. (huong dong o thuc vat xay ra tuong doi cham va duoc dieu tiet nho hoocmon thuc vat).Huong dong o thuc vat gom co : huong dong duong va huong dong am.Huong dong gom co cac kieu sau:1.Huong dat ( huong trong luc).Phan ung sinh truong cua thuc vat dap ung lai voi tac dong cua trong luc (huong ve tam qua dat).Re huong dong duong, than canh huong dong am.Giai thich:Khi dat cay nam ngang, thi re cay moc quay xuong dat vi khi do auxin tap trung nhieu o phia duoi nen o re ham luon auxin qua cao nen lam kiem ham su tang truogn cua re. O than luong auxin tap trung nhieu nhung lam cho than sinh truogn nhanh keo dai than ra=> day...