Maximum DNA synthesis during the midproliferative phase of the cycle (i.e. cycle days 8â10) correlates with the maximum number of mitoses in both the stromal and epithelial endometrial cellular elements, as well as with the midproliferative peak of plasma estradiol and nuclear estradiol receptors.
Some defining characteristics of angiosperms include flowers, carpels, and the presence of endosperm, a nutritive substance found in seeds, produced via a second fertilization event. However, some current studies suggest that endosperm is not unique to angiosperms.
Step 4: Fertilization. Sperm travel down the pollen tubes and fertilize an egg. Most angiosperms undergo double fertilization, where both an egg and the polar nuclei in the embryonic sac are fertilized. What Happens Next? After fertilization, the cells of the zygote begin dividing, and the zygote develops into an embryo, or developing plant.