NEET BIOLOGY

Detailed explanation-1: -Final answer: Growth of pollen tube towards embryo sac is Chemotropic.

Detailed explanation-2: -Entry of pollen tube into embryo sac is under the guidance of chemotropism.

Detailed explanation-3: -The two polar nuclei fuse to form a secondary nucleus or definitive nucleus which after an act of double fertilization forms triploid nutritive tissue called endosperm. The antipodal cells play some role in regulating the act of fertilization and double fertilization, but how, is not yet clearly understood.

Detailed explanation-4: -The pollen tube in a flowering plant grows in a direction that is influenced by the mechanical properties of the stigma papillae and the organization of structures called cortical microtubules inside these cells.