Difference between PEN and PEC?
The nucleus formed in the embryo sac of a seed plant by fusion of a sperm nucleus with two polar nuclei or with a nucleus formed by the prior fusion of the polar nuclei is known as PEN (primary endosperm nucleus). PEN cells are filled with reserve food materials and hence it provides nourishment to the developing embryo.
PEN cells are often called PEC (primary endosperm cells), so there is no difference.
the pollen tube extend itself and passes through synergids, then it will form two male gamates.
one gamate will move forward and fertilise with the ovum and syngamy will occur.
but anathor gamate will fuse with the two polar nucei to form PEN(PRIMARY ENDOSPERM NUCLEAUS)
THIS PROCESS IS AL;SO KNOWN AS TRIPLE FUSION.
further PEN will develop and form a cell
so, that stage will be PEC(PRIMARY ENDOSPERM CELL)
HOPE IT HELPS