Advantage
1. Since cleistogamous flowers are autogamous, there is an assured seed-set.
Disadvantage
1. Continued self-pollination leads to inbreeding depression.

Advantage
Since cleistogamous flowers are autogamous, there is an assured seed-set.
Disadvantage
Continued self-pollination leads to inbreeding depression.

1. Pollen tube carries two male gametes and the vegetative nucleus.
2. Pollen tube grows through the tissues of stigma and style to reach the ovary.
3. It enters the ovule through the micropyle and then enters the embryo sac through the filiform apparatus of one of the synergids.

Primary endosperm cell forms the kernel of coconut.
Difference
The kernel of coconut is the cellular endosperm, while the coconut water is the free-nuclear endosperm.

Primary endosperm cell forms the kernel of coconut.
Difference
The kernel of coconut is the cellular endosperm, while the coconut water is the free-nuclear endosperm.

Primary endosperm cell forms the kernel of coconut.
Difference
The kernel of coconut is the cellular endosperm, while the coconut water is the free-nuclear endosperm.

(a) Emasculation
(b) Bagging
(c) Artificial pollination.

A-Orthotropous ovule
B-Anatropous ovule
C-Hemianatropous 
D-Campylotropous ovule
E-Amphitropous ovule
F-Circinotropous ovule

(i) Banana appear to have been around as long ago as 10,000 years but because of human controlled asexual reproduction, bananas have very low genetic variety. Their gene pool is becoming have very stringent. As bananas produce no seeds,there is no way for them to diversity their do not have genetic makeup. As a result, they do not have the genetic capability to defend themselves against the funal pathogen. That's why, they are speculated on the verge of extinction within few (approximately 10 years.
(ii) The phenomenon by which fruits develop without fertilisation is called parthenocarpy
(iii) Genetic engineering might be the suggested possible technique to overcome the above-mentioned problem. Though this technique, fungal-resistant genes can be introduced in bananas to protect them from becoming extinct.

Yes, self-incompatibility impose restrictions on autogamy. The reason for this may be as majority of flowering plants produce hermaphrodite flowers and when pollen grains come in contact with stigma of the flower they continue self-pollination. Such type of continued self-pollination results in inbreeding depression. That's why flowering plants have developed many devices to discourage self-pollination and to encourage cross-pollination. One of the major ways prevent self-pollination is self-pollination is self-sterility or self-incompatibility, i.e. in some bisexual flowers, if the pollen grains fall on the stigma of the same flowers, germination does not occur. But the same pollen grains germinate when they fall on the stigma of other flowers of the same species. It is a genetical mechanism to prevent self-pollination and promote cross-pollination

(a)The process of formation of microspores or pollen grains from microspore or pollen mother cell(MMC or PMC) by meiosis is called micro-sporogenesis. It takes place in pollen sacs or microsporangia of each anther lobe.
The cellsof sporogenious tissue of microsporangium functions as potential MMC/PMC in the anther. They undergo meiosis and as a result form four microspores or pollen grains arranged tetrads. The
pollen grains separate from the tetrads and give rise to two celled male gametophytes while still in situ. In the majority of angiosperms the pollenis released from the anther at 2 celled stage while in some at 3-celled stage as the generative cell divides
(b) to form 2 male gametes

Exine: It can withstand high temperature/strong acids/alkali. It protects pollens.
Intine: It is a thin and continuous layer made up of cellulose and pectin. The intine produces pollen tube.
Vegetative cell: It is bigger and has abundant food reserve.
Generative cell: It divides mitotically to give rise to two male gametes

(a) One of the male gametes moves towards the egg cell and fuses with its nucleus thus completing syngamy. This results in the formation of a diploid cell-the zygote, the other male gamete moves
towards the two polar nuclei located in central cell and fuses with them to produce a triploid primary endosperm nucleus Since two types of fusions take place in an embryo sac the phenomenon is known as double fertilization.
(b) There occur two gametic fusions or fertilization in the female gametophyte or embryo sac of angiosperms i.e., one male gamete fuses with the egg to form zygote and the other male gamete fuses with the secondary nucleus to form the primary endosperm nucleus. The former fertilization is called as syngamy and the latter as the triple fusion. Thus, fertilization occurs twice in the same embryo sac, therefore, this is called as the double fertilization. This phenomenon is unique in angiosperms and is not found in any other group of plant kingdom other than angiosperms.

(i) (b): Y is a vascular bundle comprising xylem that transports water and mineral salts to the anther, and phloem that transports sugars to the anther.
(ii) (b): X contains pollen grains. Pollen grain contains two haploid nuclei resulting from mitosis, a generative nucleus and pollen tube/vegetative nucleus.
(iii) (c): Rough surfaces on pollen grains help them to cling onto the surface of insect pollinators.
(iv) (b): Insect-pollinated plants tend to have pollen with rough surfaces to allow them to cling more readily onto the body of insect pollinators. Their stamens are unlikely to be pendulous nor protrude outside the flower, since the pollen is not intended to be released into the air and carried away by the wind.
(v) (b): Entomophily type of pollination takes place through the agency of insects. The entomophilous flowers are brightly coloured and fragmented to attract the insects. Their pollen grains are sticky or spiny to easily get attached with the body of pollinators. When the insects visit the flowers, their body gets dusted with pollen grains, and when they fly and visit other flowers, they brush against the stigma which being sticky, at once receives the pollen grains from their body. Thus, cross-pollination is achieved.

(i) (b) 
(ii) (c) : In the given figure, processes P, Q and R represent geitonogamy (self pollination), xenogamy (cross pollination) and autogamy (self pollination), respectively. Pollinating agents are required for accomplishment of processes P and Q but no agent is required for process R. Out of P, Q and R, only Q is responsible for introducing genetic variability as it is cross pollination between different plants of same species. Salvia is insect pollinated whereas Cannabis is wind pollinated plant.
(iii) (a) :  In the given figure, processes P, Q and R represent geitonogamy (self pollination), xenogamy (cross pollination) and autogamy (self pollination), respectively. Pollinating agents are required for accomplishment of processes P and Q but no agent is required for process R. Out of P, Q and R, only Q is responsible for introducing genetic variability as it is cross pollination between different plants of same species. Salvia is insect pollinated whereas Cannabis is wind pollinated plant.
(iv) (a) : Homogamy occur in chasmogamous or open flowers where anthers and stigmas are brought together by growth, bending or folding.
(v) (b)

(c) Self-sterility is the condition in which the pollen of a flower has no fertilizing effect on the stigma of the same flower. Cross-pollination is thus the only method in them for the production of seeds. In many bisexual flowers the anther and stigma often mature at different times. This condition is known as dichogamy. Dichogamy often stands as a barrier to self pollination. There are two conditions of dichogamy.
(i) protogyny - when the gynoecium matures earlier than the anthers of the same flowers
(ii) protandry - when the anthers mature earlier than the stigma of the same flower. In both cases only cross pollination is possible.