Consider the following tissues in the stelar region of a stem showing secondary growth [2023]
(A) Primary xylem
(B) Secondary xylem
(C) Primary phloem
(D) Secondary phloem
Arrange these in the correct sequence of their position from pith towards cortex.
(A), (B), (D), (C)
(B), (A), (C), (D)
(A), (B), (C), (D)
(B), (A), (D), (C)
Identify the correct statements. [2023]
A. Lenticels are the lens-shaped openings permitting the exchange of gases.
B. Bark formed early in the season is called hard bark.
C. Bark is a technical term that refers to all tissues exterior to vascular cambium.
D. Bark refers to periderm and secondary phloem.
E. Phellogen is single-layered in thickness.
Choose the correct answer from the options given below:
A, B and D only
B and C only
B, C and E only
A and D only
(4)
Bark formed early in the season is called early or soft bark, while towards the end of the season, late or hard bark is formed. Bark is a non-technical term that refers to all tissues exterior to the vascular cambium. Phellogen is a couple of layers thick structure.
Given below are two statements. One is labelled as Assertion (A) and the other is labelled as Reason (R). [2023]
Assertion (A): Late wood has fewer xylary elements with narrow vessels.
Reason (R): Cambium is less active in winters.
In the light of the above statements, choose the correct answer from the options given below:
(A) is true but (R) is false.
(A) is false but (R) is true.
Both (A) and (R) are true and (R) is the correct explanation of (A).
Both (A) and (R) are true but (R) is not the correct explanation of (A).
(3)
In winters, the cambium is less active and forms fewer xylary elements that have narrow vessels. This wood formed is called autumn wood or late wood.
In old trees the greater part of secondary xylem is dark brown and resistant to insect attack due to [2022]
(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:
(A) and (B) only
(C) and (D) only
(D) and (E) only
(B) and (D) only
(1)
In old trees, the greater part of secondary xylem is dark brown due to deposition of organic compounds like tannins, resins, oils, gums, aromatic substances, and essential oils in the central or innermost layers of the stem.
The anatomy of springwood shows some peculiar features. Identify the correct set of statements about springwood. [2022]
(A) It is also called the earlywood.
(B) In spring season, cambium produces elements with narrow vessels.
(C) It is lighter in color.
(D) The springwood along with autumn wood shows alternate concentric rings for annual rings.
(E) It has lower density.
Choose the correct answer from the options below:
(A), (B), (D), and (E) only
(A), (C), (D), and (E) only
(A), (B), and (D) only
(C), (D), and (E) only
(2)
In the spring season, cambium is very active and produces a large number of xylary elements having vessels with wider cavities in springwood.
Match List-I with List-II. [2021]
| List-I | List-II |
| (p) Lenticels | (i) Phellogen |
| (q) Cork cambium | (ii) Suberin deposition |
| (r) Secondary cortex | (iii) Exchange of gases |
| (s) Cork | (iv) Phelloderm |
Choose the correct answer from the options given below.
p-(iv), q-(ii), r-(i), s-(iii)
p-(iv), q-(i), r-(iii), s-(ii)
p-(iii), q-(i), r-(iv), s-(ii)
q-(ii), q-(iii), r-(iv), s-(i)
(3)
Select the correct pair. [2021]
Loose parenchyma cells rupturing the epidermis and forming a lens-shaped opening in bark - Spongy parenchyma
Large colorless empty cells in the epidermis of grass leaves - Subsidiary cells
In dicot leaves, vascular bundles are surrounded by large thick-walled cells - Conjunctive tissue
Cells of medullary rays that form part of cambial ring cambium - Interfascicular cambium
(4)
The cells of medullary rays, adjoining the intrafascicular cambium become meristematic and form the interfascicular cambium.
Identify the incorrect statement. [2020]
Heartwood does not conduct water but gives mechanical support.
Sapwood is involved in conduction of water and minerals from root to leaf.
Sapwood is the innermost secondary xylem and is lighter in color.
Due to deposition of tannins, resins, oils, etc., heartwood is dark in color.
(3)
Sapwood is the peripheral or outermost region of the secondary xylem and lighter in color.
Which of the statements given below is not true about the formation of annual rings in trees? [2019]
Annual rings are not prominent in trees of temperate region.
Annual ring is a combination of spring wood and autumn wood produced in a year.
Differential activity of cambium causes light and dark bands of tissue—early and late wood respectively.
Activity of cambium depends upon variation in climate.
(1)
The activity of cambium is under the control of many physiological and environmental factors. In temperate regions, the climatic conditions are not uniform throughout the year. In the spring season, cambium is very active and produces a large number of xylary elements having vessels with wider cavities. The wood formed during this season is called spring wood or early wood. In winter, the cambium is less active and forms fewer xylary elements that have narrow vessels, and this wood is called autumn wood or late wood. The spring wood is lighter in color and has a lower density, whereas the autumn wood is darker and has a higher density. The two kinds of woods that appear as alternate concentric rings constitute an annual ring.
Secondary xylem and phloem in dicot stem are produced by [2018]
apical meristems
vascular cambium
phellogen
axillary meristems
(2)
Vascular cambium is a type of lateral meristem that produces secondary tissues (xylem and phloem) during secondary growth. It is produced by two types of meristem: intrafascicular cambium (primary meristem occurring as a strip in vascular bundles) and interfascicular cambium (secondary meristem which develops from permanent cells of medullary rays which occur at the level of intrafascicular strips). The cells of vascular cambium are of two types: fusiform initials, which produce secondary xylem towards the outside and secondary phloem towards the inner side, and ray initials, which give rise to vascular rays.
