In old trees the greater part of secondary xylem is dark brown and resistant to insect attack due to :
a. | secretion of secondary metabolites and their deposition in the lumen of vessels. |
b. | deposition of organic compounds like tannins and resins in the central layers of stem. |
c. | deposition of suberin and aromatic substances in the outer layer of stem. |
d. | deposition of tannins, gum, resin and aromatic substances in the peripheral layers of stem. |
e. | presence of parenchyma cells, functionally active xylem elements and essential oils. |
Choose the correct answer from the options given below
1. (b) and (d) Only
2. (a) and (b) Only
3. (c) and (d) Only
4. (d) and (e) Only
The anatomy of springwood shows some peculiar features. Identify the correct set of statements about springwood.
a. | It is also called as the early wood. |
b. | In spring season cambium produces xylem elements with narrow vessels. |
c. | It is lighter in colour. |
d. | The springwood along with autumn wood shows alternate concentric rings forming annual rings. |
e. | It has lower density. |
Choose the correct answer from the options given below:
1. (c), (d) and (e) Only
2. (a), (b), (d) and (e) Only
3. (a), (c), (d) and (e)Only
4. (a), (b) and (d) Only
Axillary buds are derived from the activity of :
1. Lateral meristem
2. Secondary meristem
3. Apical meristem
4. Intercalary meristem
Select the correct statements related to the activity of cork cambium:
1. | The outer cells differentiate into phelloderm. |
2. | The cork differentiated from cork cambium, is impervious to water due to deposition of tannins and resins. |
3. | Cuts the cells only on the outer side. |
4. | Cuts the cells on inner as well as outer side. |
Which of the following is not a character of collenchyma tissue?
1. | They provide mechanical support to the growing part of the plant |
2. | They occur in layers below epidermis in dicotyledonous plants |
3. | They consist of cells with thick corners due to cellulose deposition |
4. | They are usually dead and without protoplasts |
A: | Long-distance flow of photoassimilates in plants occurs through sieve tubes. |
R: | Mature sieve tubes have parietal cytoplasm and perforated sieve plates. |
1. | If both Assertion & Reason are true and the reason is the correct explanation of the assertion. |
2. | If both Assertion & Reason are true but the reason is not the correct explanation of the assertion. |
3. | If the Assertion is a true statement but the Reason is false. |
4. | If both Assertion and Reason are false statements. |