Question

Allogamy is favoured by
(a) Homogamy
(b) Cleistogamy
(c) Monocliny
(d) Dicliny

Answer 1

Hint: In this plant bearing unisexal flower posses only one kind of sex organ either male or female. Allogamy is also known as xenogamy or cross pollination. Examples for this are: papaya or mulberry.

Complete step by step answer:
Dicliny: When male and female flowers are separate but present on the same plants, it is known as monoecy. In a few of the crops, the male and female flowers are present on the same inflorescence like in mango, castor and banana. In a few of the cases, they are on separate inflorescence as in maize. When staminate and pistillate flowers are present on the different plants, it is called dioecy. Which includes papaya, date palm, spinach, hemp and asparagus. This refers to unisexual flowers. This is of two types: i) monoecy and ii) dioecy.

So, the correct answer is, ‘Dicliny.’

Additional Information:
- The process by which pollen grains are transferred from anthers to stigma is referred to as pollination. - Pollination is of two types: Autogamy or self pollination and Allogamy or cross pollination.
Autogamy
- The transfer of pollen grains or male gamete from the anther to the stigma of the same flower is known as autogamy or self pollination.
- Autogamy is the closest form of inbreeding.
- Autogamy leads to homozygosity.
- Such species develop homozygous and do not exhibit significant inbreeding depression.
Mechanism promoting self- pollination:
- Bisexuality: The presence of male and female organs within the same flower is known as bisexuality. The presence of bisexual flowers is a important for self pollination. All the self pollinated plants have hermaphrodite flowers.
- Homogamy: The maturation of anthers and stigma of a flower at the same time is called homogamy. As a rule, homogamy is essential for self- pollination.
- Cleistogamy: Occurs when pollination and fertilization occur in unopened flower buds, it is known as cleistogamy. It ensures self pollination and prevents cross pollination.
- Chasmogamy: The opening of flowers only after the completion of the pollination process is known as chasmogamy. This is found in crops like wheat, barley, rice and oats.
Examples are greengram, blackgram, soybean, chickpea and pea.

Note:
Allogamy
Allogamy is the transfer of pollen grains or male gamete from the anther of one plant to the stigma of another plant is also termed as allogamy or cross pollination. This is the common form of out- breeding.
Allogamy leads to heterozygosity.
Mechanism promoting cross- pollination:
- Dichogamy: This refers to maturation of anthers and stigma of the same flowers at different times. Dichogamy promotes cross pollination even during the hermaphrodite species. Dichogamy is of two types:
i) protogyny
ii) protandry
- Heterostyly: When stiles and filaments in a flower are of different lengths, it is called heterostyly. It promotes cross pollination, such as linseed.