Q: Explain pressure flow hypothesis of translocation of sugars in plants?
A: Phloem transports food (sucrose) from the source to the sink in the form of sap. Source (leaf) and sink (other parts and storage organs) relationship is variable. Phloem sap consists water, sucrose, other sugars, hormones and amino acids. The translocation in phoem is bidirectional as source-sink relationship
is variable. The transport in phloem is explained by pressure flow hypothesis. It was proposed by Munch.
It is also called Mass flow hypothesis. It occurs in 2 steps.
(1) Loading (2) Unloading.
Loading of Phloem:
1. Glucose in the mesophyll cells (source) is converted to sucrose.
2. Sucrose moves to companion cells.
3. It moves from there to sieve tube cells by active transport.
4. Concentration of sap in these cells become hypertonic.
5. Water from Xylem cells moves by osmosis into sieve tube cells.
6. Mass and Pressure increase.
Unloading:
1. As mass increases in sieve tube cells, pressure flow begins.
2. Sugars in the sink are used up.
3. Sap in the cells become hypotonic.
4. Water moves out of the phoem.
5. Water potential gradient is established between sink and source.
6. Sugars are unloaded. They move into the cells which use sugar.
10th Physical Sciences Important Questions and Answers
Mirage is an optical illusion where it appears that water has collected on the road at a distant place but when we get there, we do not find any water. This phenomenon is because of total internal reflection.
Q: Explain the formation of a mirage? (4 Marks)
A: 1) During a hot summer day, air just above the road is very hot and the air at higher altitudes is cool.
2) It means that the temperature decreases with height. As a result the density of air increases with height.
3) We know that the refractive index of air increases with density. Thus the refractive index of air increases with height.
4) So the cooler air at the top has greater refractive index than the hotter air just above
the road.
5) Light travells faster through the thinner hot air than through the denser cool air above it.
6) When light from a tree passes through a medium just above the road, whose refractive index decreases towards the ground, it suffers, refraction and takes a curved path because of total internal reflection.
7) This appears to the observer as if the ray is reflected from the ground. Hence we feel the illusion of water being present on the road.
8) The inverted virtual image of the tree is seen by the observer. This is a mirage.
Q: Explain the formation of a mirage? (4 Marks)
A: 1) During a hot summer day, air just above the road is very hot and the air at higher altitudes is cool.
2) It means that the temperature decreases with height. As a result the density of air increases with height.
3) We know that the refractive index of air increases with density. Thus the refractive index of air increases with height.
4) So the cooler air at the top has greater refractive index than the hotter air just above
the road.
5) Light travells faster through the thinner hot air than through the denser cool air above it.
6) When light from a tree passes through a medium just above the road, whose refractive index decreases towards the ground, it suffers, refraction and takes a curved path because of total internal reflection.
7) This appears to the observer as if the ray is reflected from the ground. Hence we feel the illusion of water being present on the road.
8) The inverted virtual image of the tree is seen by the observer. This is a mirage.
SSC English Grammar - Prepositions Model Questions as per new Syllabus in AP and Telangana
A preposition is a word that is used before a noun or pronoun to show
its relation with other words in a sentence.
Eg: Kartheek spoke to Abhinav with his hands in his pockets.
Some Commonly Used Prepositions: in, on, at, to, for, from, before,
after, beside, behind, about, against, over, during, between, through,
round, along, across, towards, among, etc.
1. Will you be able to meet me at school? (at indicates place.)
2. My uncle lives in Japan. (in indicates place.)
3. She died of cholera. (of indicates reason.)
4. He is a son of poor parents. (of indicates possession.)
5. I got up late in the morning. (in indicates time.)
Examples:
1. It's ten by my watch. (Not in my watch)
2. Vaseema spoke to me on phone. (Not with me)
3. We watch cricket on TV. (Not in TV.)
4. Shruthi caught Preethi by her arm (Not with her arm.)
5. There are some birds in the tree. (Not on the tree.)
6. Abhinav has just left for hyderabad. (Not left to...)
Fill in the blanks with suitable prepositions.
1. The cat is hiding .... us ..... the table.
2. I shall return your dictionary .... a week or two.
3. My cousin is older ...... me ..... two years.
4. Kashmir is the bone of content ........ India and Pakistan.
5. Take ....... your dirty shirt and put ...... a new one.
6. Are you satisfied ....... your performance in test?
7. The godown is infested ...... rats.
Answers:
1. from, under 2. in 3. than, by 4. between 5. off, on 6. with 7. with
its relation with other words in a sentence.
Eg: Kartheek spoke to Abhinav with his hands in his pockets.
Some Commonly Used Prepositions: in, on, at, to, for, from, before,
after, beside, behind, about, against, over, during, between, through,
round, along, across, towards, among, etc.
1. Will you be able to meet me at school? (at indicates place.)
2. My uncle lives in Japan. (in indicates place.)
3. She died of cholera. (of indicates reason.)
4. He is a son of poor parents. (of indicates possession.)
5. I got up late in the morning. (in indicates time.)
Examples:
1. It's ten by my watch. (Not in my watch)
2. Vaseema spoke to me on phone. (Not with me)
3. We watch cricket on TV. (Not in TV.)
4. Shruthi caught Preethi by her arm (Not with her arm.)
5. There are some birds in the tree. (Not on the tree.)
6. Abhinav has just left for hyderabad. (Not left to...)
Fill in the blanks with suitable prepositions.
1. The cat is hiding .... us ..... the table.
2. I shall return your dictionary .... a week or two.
3. My cousin is older ...... me ..... two years.
4. Kashmir is the bone of content ........ India and Pakistan.
5. Take ....... your dirty shirt and put ...... a new one.
6. Are you satisfied ....... your performance in test?
7. The godown is infested ...... rats.
Answers:
1. from, under 2. in 3. than, by 4. between 5. off, on 6. with 7. with
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