In wheat and rice,pollen grains lose viability within $30$ minutes of their release. In members of the families Rosaceae,Leguminosae,and Solanaceae,the viability is maintained for $...$.

.......... and .......... pollen lose viability within $30$ minutes of their release.

Through which cell of the embryo sac does the pollen tube enter the embryo sac?

$A$: Initial growth of the pollen tube takes place at the expense of food present in the stigma and style.
$R$: The pollen tube travels intracellularly and chemotactically.

Identify the correct sequence of events of pollen-pistil interaction given below.
$(a)$ Pollen tube grows through the stigma,style and reaches the ovule.
$(b)$ Pollen grain lands on the stigma.
$(c)$ Pollen germinates to form pollen tube.
$(d)$ Pollen tube carrying $2$ male gametes enters the ovule.
Choose the correct option.

What does the filiform apparatus do at the entrance into the ovule?