The incorrect pairing is Ulothrix – Mannitol. Ulothrix, a green alga, stores starch as its reserve food, not mannitol. Mannitol is commonly a storage carbohydrate in brown algae (phaeophytes) and some other algae, but not in Ulothrix as per NCERT. The other pairs are correct: Ectocarpus contains fucoxanthin (brown pigment); Porphyra stores Floridean starch (red algae); Volvox stores starch (green alga).
🧠 Did You Know?
Floridean starch is the storage carbohydrate characteristic of red algae (Rhodophyta).
💡 NCERT Memory Line:
Green algae like Ulothrix store starch; brown algae have fucoxanthin; red algae have Floridean starch.
Identify the correct set of statements :
A.The leaflets are modified into pointed hard thorns in Citrus and Bougainvillea.
B.Axillary buds form slender and spirally coiled tendrils in cucumber and pumpkin.
C.Stem is flattened and fleshy in Opuntia and modified to perform the function of leaves.
D.Rhizophora shows vertically upward growing roots that help to get oxygen for respiration.
E.Subaerially growing stems in grasses and strawberry help in vegetative propagation.
Choose the correct answer from the options given below :
Read the following statements about the vascular bundles :
A. In roots, xylem and phloem in a vascular bundle are arranged in an alternate manner along the different radii.
B. Conjoint closed vascular bundles do not possess cambium.
C. In open vascular bundles, cambium is present in between xylem and phloem.
D. The vascular bundles of dicotyledonous stem possess endarch protoxylem.
E. In monocotyledonous root, usually there are more than six xylem bundles present.
Choose the correct answer from the options given below :
Explanation:
From NCERT:
- B: Conjoint closed vascular bundles do not have cambium (true).
- C: In open vascular bundles, cambium is present between xylem and phloem (true).
- D: Dicot stem vascular bundles show endarch protoxylem (true).
- E: Monocot root typically has more than six xylem bundles (true, polyarch arrangement).
- A is not consistent with NCERT: in roots, the arrangement is radial and the vascular bundles are organised with xylem and phloem in a specific radial pattern, but the phrasing “alternate along the different radii” does not correctly describe the standard root bundle arrangement. Therefore A is not a correct standalone statement. Thus the correct combination is B, C, D and E.
? Did You Know?
In monocot roots, there is more than one xylem bundle forming a radial pattern around the central pith, unlike the typical dicot root.
? NCERT Memory Line:
Open vascular bundles have cambium between xylem and phloem; dicot stem shows endarch protoxylem; monocot root often has many xylem bundles (polyarch).
In old trees the greater part of secondary xylem is dark brown and resistant to insect attack due to:
A. secretion of secondary metabolities 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:
Explanation:
In old trees, the inner, old secondary xylem stores secondary metabolites like tannins and resins that darken the wood and deter insect attack. These compounds are deposited in central layers of the stem and in the luminal walls of vessels, giving the wood its dark brown color and resistance. This corresponds to options A and B.
? Did You Know?
NCERT explains that secondary metabolites accumulate in the central tissues of old xylem, contributing to durability and defense.
? NCERT Memory Line:
Secondary xylem in old trees becomes dark due to deposition of tannins, resins, and other metabolites in central layers and vessel lumens.
