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Selina Solutions Class 9 Biology Solutions for Exercise in Chapter 5 - Pollination And Fertilization

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Question 17 Exercise
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Given alongside is a diagrammatic sketch of the sectional view of a germinating pollen grain. Study the same and then answer the questions that follow:

(a) Name the parts labeled 1,2,3,4, and 5

(b) Where does the germination of the pollen grain take place and how?

(c) What is the function of the part labeled ‘4’?

(d) What happens to the part labeled ‘5’ during the process? Question 17 Image - Selina Solutions CONCISE Biology - Class 9 ICSE chapter Pollination And Fertilization

Answer:

(a) The following are the labeled parts of the germinating pollen grain:

1 – Exine

2 – Intine

3 – Pollen tube

4 – Tube nucleus

5 – Generative nucleus

(b) The germination of the pollen grain takes place only if it falls on the stigma of the same plant species. Else, it disintegrates. It is stimulated to germinate upon falling on the stigma as stigma secretes sugars.

(c) The labeled part ‘4’ is the tube nucleus. Its function is to direct the growth of the pollen tube towards the ovary.

(d) The labeled part ‘5’ is the generative nucleus. It is located at the tip of the pollen tube during germination of the pollen grain and splits into two sperm nuclei. The entrance of the pollen tube into one of the synergids causes it to release two of its sperm nuclei, one of which enters the egg cell fusing with nucleus, the other sperm nucleus approaches the two polar nuclei in the central cell fusing with them

Video transcript
"hello everyone welcome to little this is priya and here we have a question about the structure of pollen grain let us look into the question given alongside is a diagrammatic sketch of sectional view of germinating pollen green study the same and then answer the questions that follow name the parts labeled 1 2 3 4 and 5. let us look into this label parts the first part is the egg sign which is the outermost layer of fallen green and the second part is in time which is a innermost layer of pollen grain third is a pollen tube which shows goes to the view and helps the male gametes to enter into ovule this is a pollen tube and the fourth one is tube nucleus which helps for germination of pollen tube tube nucleus and the fifth one is generative nucleus which helps in formation of two male gametes and the fifth one is generative nucleus this is about this parts and let us look into the next question where does the germination of pollen tube takes place and how germination of pollen tube takes place on the stigma of a flower so when after the pollination when the pollen tube and then the pollen grain falls on the stigma on the same species of plant then this pollen grain germinates else if it is another kind of flower which is belonging to different species then it disintegrates and this pollen tube is germinated is stimulated to germinate upon falling on the stigma of the same species secreting sugars so in this way the pollen grain can germinate once it when it falls on the stigma so when this pollen grain belongs to the same kind of flour then the stigma secretes some juices secretes some sugars which helps in germination of pollen grain next question what is the function of the part labeled for so labeled 4 is a pollen this body tube nucleus and this tube nucleus helps to direct the growth of pollen tube towards the ovary out towards the ovary so this part two helps the pollen tube to move towards the oval for fertilization and fourth question is what happens to the part labeled 5 during the process the 5 which is a generative nucleus it helps in formation of two male gametes so after when these generated nucleus moves through these pollen tube the generative nucleus will forms two male gametes they form two male gametes and these two male gametes enters into ovule through a micropine and one male gamete fuses with egg fuses with egg one male gamete fuses with egg and produces zygote and the other male gamete fuses with the polar nuclei present in ovule other male gamete fuses with polar nuclei and forms and forms endosperm so double fertilization takes place with the help of these two male gametes this fusion we called double fertilization and in this way the label 5 generative nucleus helps in producing two male gametes and one male gamete fuses with egg and the other male gamete fuses with polar nuclei and this fertilization is called double fertilization hope you understand this video if you like my video please subscribe to a little channel and if you have any doubts you can keep a message in comment box thank you"
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