Question

Can any one explain me how many mitosis,meosis,spindle apparatus are formed in pollen grain and ovule(megasporangium)?

Answer 1

ok here is your ans Animals cells all have centrioles as organizing bodies with gamma tubulin while plant nuclear membranes have gamma tubulin in multiple dispersed sites rather than a discrete organizing body. 

Plants have an alternate path for mitotic microtubule spindle formation since they do not use organizing bodies. Spindle microtubules nucleate in multiple dispersed sites on a plant's nuclear envelope containing gamma tubulin ring nucleation assemblies. Plant gamma-tubulin interacts with alpha beta-tubulin dimers and forms membrane-associated complexes. 

This assembly is regulated by TPX2 protein. Plants have adapted nuclear–cytoplasmic shuttling of TPX2 to maintain proper spindle assembly without centrosomes. TXP2 protein is made and sent to the nucleus with a nuclear localization signal. It is exported by its nuclear export signal sequence activity at the G2/M transition to initiate the assembly of the prospindle. 
Acentrosomal microtubule nucleation in higher plants