Part 6 — Developmental Morphology, Anatomy & Vascular Tissues (Questions 126–150)
Part 6 — Developmental Morphology, Anatomy & Vascular Tissues (Questions 126–150)
Q126. Primary growth in plants is due to activity of:
A) Lateral meristems only
B) Apical meristems at shoot and root tips leading to increase in length and formation of primary tissues (protoderm, ground meristem, procambium)
C) Guard cells only
D) Epidermis only
Answer: B
Explanation:
A) Lateral meristems cause secondary growth.
B) Correct.
C/D) Not main growth drivers.
Q127. Xylem conducts:
A) Organic nutrients like sucrose only
B) Water and mineral salts unidirectionally from roots to aerial parts; xylem comprises tracheids, vessels (in angiosperms), xylem parenchyma and fibres
C) Pollen transport only
D) Photosynthesis only
Answer: B
Explanation:
A) Phloem transports organic solutes.
B) Correct.
C/D) Incorrect.
Q128. Phloem transports:
A) Water and minerals only
B) Organic products (sucrose, amino acids) bidirectionally via sieve tubes and companion cells in angiosperms (pressure flow hypothesis explains translocation)
C) Only hormones
D) Only proteins
Answer: B
Explanation:
A/C/D) Partial or incorrect.
B) Correct.
Q129. Sieve tube elements in angiosperms are associated with:
A) Companion cells (derived from same mother cell) that facilitate loading/unloading and metabolic support for sieve elements which lack nuclei at maturity
B) Guard cells only
C) Tracheids only
D) Root hairs only
Answer: A
Explanation:
A) Correct.
B/C/D) Not related.
Q130. Secondary xylem formed by vascular cambium accumulates as:
A) Bark only
B) Wood (secondary xylem) which forms annual rings in temperate climates due to seasonal variation in vessel/tracheid size producing growth rings; important timber source
C) Petiole only
D) Root hair only
Answer: B
Explanation:
A) Secondary phloem + periderm = bark.
B) Correct.
C/D) Irrelevant.
Q131. The tissue that replaces epidermis in secondary growth is called:
A) Xylem only
B) Periderm (formed of cork cambium/phellogen, cork/phellem and phelloderm) — provides protection and forms bark with secondary phloem
C) Mesophyll only
D) Endodermis only
Answer: B
Explanation:
A/C/D) Not replacement tissues.
B) Correct.
Q132. Wood with distinct growth rings (ring-porous wood) is typical of:
A) Tropical trees with continuous growth only
B) Temperate trees where spring wood has large vessels and summer wood has smaller vessels, producing rings used for dendrochronology
C) Herbaceous plants only
D) Annuals only
Answer: B
Explanation:
A/C/D) Not generally ring-forming.
B) Correct.
Q133. Adventitious buds may arise from:
A) Only apical meristem always
B) Any non-meristematic tissue that reactivates meristematic activity such as pericycle/stem cortex in vegetative propagation (e.g., buds on potato tuber eyes)
C) Only from flowers
D) Root cap only
Answer: B
Explanation:
A/C/D) Not exclusive.
B) Correct.
Q134. The vascular cambium arises from:
A) Procambium only in stems and from pericycle in roots (contribution to cambium formation varies in organs) and produces secondary xylem to inner side and secondary phloem to outer side
B) Epidermis only
C) Cork cambium only always
D) None of the above
Answer: A
Explanation:
A) Correct.
B/C/D) Incorrect.
Q135. In monocotyledonous stems secondary growth is usually absent because:
A) Monocots lack vascular bundles
B) Monocots generally lack a continuous ring of vascular cambium; some monocots show anomalous secondary thickening via primary thickening meristem or cambia in species like Dracaena
C) Monocots have woody secondary xylem usually
D) Monocots always have cambium
Answer: B
Explanation:
A/C/D) Incorrect.
B) Correct nuance: most monocots do not exhibit typical secondary growth.
Q136. The function of xylem fibres is:
A) Conduct water only
B) Provide mechanical support and strength due to lignified cell walls; xylem parenchyma conducts storage and lateral transport
C) Photosynthesis only
D) Pollen dispersal
Answer: B
Explanation:
A/C/D) Not fibre function.
B) Correct.
Q137. Sclerenchyma cells are:
A) Living at maturity and involved in secretion
B) Dead at maturity with thick lignified walls providing support (fibres and sclereids) and often forming hard tissues like nutshells and seed coats
C) Found in phloem only
D) Always flexible living cells
Answer: B
Explanation:
A/C/D) Incorrect.
B) Correct.
Q138. Collenchyma tissue provides:
A) Lignified rigidity only
B) Flexible mechanical support to growing regions (longitudinally thickened primary cell walls rich in pectin) found beneath epidermis in stems and petioles
C) Storage only
D) Xylem conduction only
Answer: B
Explanation:
A/C/D) Not precise.
B) Correct.
Q139. The wood of gymnosperms is generally termed:
A) Hardwood (angiosperm wood with vessels)
B) Softwood (largely tracheid-based wood of gymnosperms, less vessel presence)
C) Manoxylic only
D) None
Answer: B
Explanation:
A) Hardwood = angiosperms.
B) Correct.
C) Manoxylic is a wood type but not sole term.
Q140. Rays in secondary xylem are formed by:
A) Cambial activity producing parenchymatous rays for radial transport and storage, connecting secondary xylem and phloem horizontally
B) Epidermis only
C) Root hairs only
D) Stomata only
Answer: A
Explanation:
A) Correct.
B/C/D) Incorrect.
Q141. Lenticels form during:
A) Primary growth only
B) Secondary growth when periderm replaces epidermis, where cork cambium produces secondary protective tissue and lenticels form for gas exchange
C) Flowering only
D) Fruit formation only
Answer: B
Explanation:
A/C/D) Not accurate.
B) Correct.
Q142. Secondary phloem differs from primary phloem by:
A) Being produced by vascular cambium and contributing to bark; but both transport organic solutes — secondary phloem accumulates externally and may form part of bark while primary phloem is part of primary vascular bundle
B) Being made of xylem only
C) Being absent in woody plants
D) Not transporting anything
Answer: A
Explanation:
A) Correct.
B/C/D) Incorrect.
Q143. In leaf traces the vascular bundles connecting stem and leaf are derived from:
A) Ground tissue only
B) Procambium of shoot apex which branches into stem and leaf traces during primary growth; leaf trace forms leaf vascular bundle connecting to stem vascular system
C) Epidermis only
D) Cork only
Answer: B
Explanation:
A/C/D) Not correct.
B) Correct.
Q144. A tylosis is:
A) Formation of outgrowths (parenchymatous) into vessels from adjacent xylem parenchyma during heartwood formation, blocking vessels and contributing to wood durability and color changes in heartwood
B) A type of leaf appendage
C) A pollen grain variant
D) A root hair type
Answer: A
Explanation:
A) Correct.
B/C/D) Not relevant.
Q145. Laticifers in plants produce:
A) Sugars only
B) Latex (milky fluid) containing resins, alkaloids and proteins, common in families like Euphorbiaceae, Apocynaceae and some Solanaceae
C) Only water
D) Starch only
Answer: B
Explanation:
A/C/D) Not latex components.
B) Correct.
Q146. In secondary growth, which of the following tissues contributes to the formation of bark?
A) Secondary xylem only
B) Secondary phloem + periderm (phellogen/cork + phelloderm) together form bark (outer protective layers)
C) Epidermis only
D) Mesophyll only
Answer: B
Explanation:
A/C/D) Not full.
B) Correct.
Q147. Anastomosing borders in vessels refer to:
A) Vessel elements being isolated only
B) Perforation plates and pits that create continuous water-conducting channels; in vessels, perforation plates and bordered pits allow vertical and lateral water movement — “anastomosing” refers to interconnection of vessels
C) Leaf stomata arrangement only
D) Inflorescence pattern
Answer: B
Explanation:
A/C/D) Not correct.
B) Correct concept.
Q148. Secondary thickening in some monocots (anomalous secondary growth) is due to:
A) Vascular cambium only always
B) Activity of a secondary (anomalous) cambia or primary thickening meristem producing successive cambia or vascular bundles enlargement as in Dracaena, Yucca (forming “secondary” tissues)
C) Root hairs only
D) Leaf pulvinus only
Answer: B
Explanation:
A) Typical dicot mechanism.
B) Correct for certain monocots.
C/D) Irrelevant.
Q149. In woody plants, heartwood differs from sapwood in that heartwood:
A) Is actively conducting water
B) Is darker, non-conducting, impregnated with extractives and decay-resistant compounds, while sapwood is outer lighter wood conducting xylem sap and storing reserve materials
C) Is living tissue with meristematic activity
D) Contains stomata
Answer: B
Explanation:
A/C/D) Incorrect.
B) Correct.
Q150. The primary meristem layer that gives rise to epidermis is:
A) Procambium only
B) Protoderm (outermost primary meristem) differentiates into epidermis
C) Ground meristem only
D) Vascular cambium only
Answer: B
Explanation:
A/C/D) Other meristem derivatives.
B) Correct.