Question

What are the different adaptations for cross pollination ? Explain with example

Answer 1

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☑ Majority of plants produce hermaphrodite (Bisexual) flowers and pollen grains are likely to come in contact with the stigma of the same flower.

☑ Continued self pollination results in inbreeding depression.

☑ Flowering plants have developed many ADAPTIONS or CONTRIVANCES or OUTBREEDING DEVICES to discourage self pollination and to encourage cross-pollination.

☑There are different types of OUTBREEDING DEVICES or ADAPTATIONS :

$\large{ \bf{ \orange{DICHOGAMY : }}}$
✴The condition in which the Androecium and Gynoecium of a bisexual flower mature at different times.

✴In other words, Improper Synchronising of pollen release and stigma receptivity.

✴It is of two types :

$\blue{ \bf{1)PROTANDRY : }}$

✔ Androecium matures earlier than gynoecium.

✔ The entire pollen fall off from stamens ,by the time gynoecium matures.

✔ Example : Helianthus (Sunflower) , Gossypium(cotton)......


$\purple{ \bf{2)PROTOGYNY : }}$

✔ Gynoecium matures earlier than Androecium.

✔Thus , by the time the gynoecium matures, the stamens remain in immature condition.

✔ Example :Datura , Solanum.....


$\large{ \bf{ \red{HERKOGAMY :}}}$
✴The condition in which the anther and Stigma are placed at different positions so that the pollen cannot come in contact with the stigma of the same flower.

✴ Example :
♦ Stigma project beyond stamens in Hibiscus.
♦ Stigmas bend in opposite direction to stamens in Gloriosa superba.


$\green{ \large{ \bf{SELF \: STERILITY : }}}$
✴ The genetic mechanism which prevents self pollen from fertilizing the ovules by inhibiting pollen germination or pollen tube growth in the pistil.

✴It is also called self compatibility.

✴ Example : Abutilon.

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