10th Class Science Control and Coordination

  • question_answer 44)
      The growth of pollen tubes towards ovules is due to (a) hydrotropism              (b) chernotropism           (c) geotropism                  (d) phototropism

    Answer:

                      (b) The growth of a pollen tube towards ovule is induced by a chemical (sugar) substance secreted by the ripened stigma of flower into the style towards ovary. It is an example of chernotropism, pollen grain responds to stimulus by growing a pollen tube in downward direction, towards ovule for fertilization.


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