Question

Rarely among angiosperms, the pollen grains influenced the endosperm. This is called as
(A) Metaxenia
(B) Nemec phenomenon
(C) Xenia
(D) Mesogamy

Answer 1

Hint: Endosperm is a product of triple fusion and develops from central cell of embryo sag It is generally a triploid tissue The cells of this tissue are filled with reserve food materials and are used for the nutrition of the developing embryo. It is absent in families such as Orchidaceous, Podostemaceae and Trapaceae.

Complete answer:
The classical example of pollen grain influence on endosperm can be seen in maize commonly known as Mays. The different colour of maize can be seen due to the assortment of alleles influenced by pollen grains. This type of maize is used for decorative purposes.
Now let us match this with the options given:
Metaxenia: Discovered by Swingle. The effect of foreign pollen on somatic tissue lying outside the endosperm is known as metaxenia. Thus, this option is not correct.
Nemec phenomenon: The embryo sacs of pollen are known as nemec phenomenon as they are discovered by Nemec. Thus, this option is not correct.
Xenia :- The effect of foreign pollen on the endosperm character is called xenia. This term was given by Focke. This was first observed in maize e.g. endosperm colour. Thus, this option is correct.
Mesogamy :- When pollen tube enters the ovule through the middle part of it is called mesogamy. It is commonly observed in cucurbits. Thus, this option is not correct.

Our correct answer is c that is Xenia.

Note: There are many types of endosperms as :- Ruminate Endosperm: Endosperm having surface irregularity. e.g. Passiflora, Annona Myristica. Mosaic Endosperm: Endosperm with different colour patches. e.g), Maize. The seeds with double endosperm are found in coconut (Cocos nucifera), (a) liquid endosperm, (b) cellular endosperm. The stony endosperm is present in betel nut (areca nut) and date palm (Phoenix dactylifera).