Assertion (A): Dianthus and Primrose show free central placentation. Reason (R): In these plants, the ovules are borne on a central axis and septa are completely absent.
In free central placentation (exemplified by Dianthus and Primrose), ovules are borne on a central axis and septa (walls) are completely absent, making the ovary single-chambered.
Question 152 of 300
📘 CLASS XI
Statement I: If a fruit is formed without fertilisation of the ovary, it is called a parthenocarpic fruit. Statement II: Parthenocarpic fruits generally contain large, healthy endospermic seeds. Select the correct option:
Statement I is correct. Statement II is incorrect because parthenocarpic fruits (formed without fertilisation) are seedless, as seeds develop from fertilized ovules.
Question 153 of 300
📘 CLASS XI
Assertion (A): Mango and coconut are classified as drupes. Reason (R): They develop from monocarpellary superior ovaries and are characteristically one-seeded.
Mango and coconut are drupes. They develop from a monocarpellary, superior ovary and contain a single seed. The botanical definition of a drupe includes these developmental and carpellary characteristics, making R the correct explanation of A.
Question 154 of 300
📘 CLASS XI
Statement I: In dicotyledonous seeds, the outer covering (seed coat) has two distinct layers: the outer testa and the inner tegmen. Statement II: The hilum is a small pore on the seed coat through which water enters during germination, located above the micropyle. Select the correct option:
Statement I is correct. Statement II is incorrect because the hilum is the scar where the developing seed was attached to the fruit, and the micropyle is the small pore located above the hilum (not the other way around).
Question 155 of 300
📘 CLASS XI
Assertion (A): Non-endospermic seeds are those where the endosperm is completely consumed during embryo development before seed maturity. Reason (R): Castor is a classic example of a non-endospermic seed.
The Assertion is true. The Reason is false because castor is an endospermic (food-storing endosperm) seed, while beans, grams, and peas are non-endospermic.
Question 156 of 300
📘 CLASS XI
Statement I: In monocotyledonous seeds of cereals like maize, the seed coat is separate and can be easily peeled off from the fruit wall. Statement II: The outer proteinous layer that separates the embryo from the endosperm in maize is called the aleurone layer. Select the correct option:
Statement I is incorrect because in maize and other cereals, the seed coat is membranous and generally fused with the fruit wall. Statement II is correct; the aleurone layer is a proteinous outer covering of the endosperm that separates the embryo.
Question 157 of 300
📘 CLASS XI
Assertion (A): In the floral formula of Brassicaceae (mustard), the symbol K2+2 represents a polysepalous calyx arranged in two whorls of two sepals each. Reason (R): The numbers are written as 2+2 rather than 4, indicating that the four sepals are not in a single concentric ring.
In the floral formula, K2+2 represents a calyx of 4 sepals arranged in two whorls (2 outer, 2 inner). This spatial, dimerous arrangement is indicated by the "+" symbol, showing arrangement in separate whorls rather than a single concentric whorl of 4.
Question 158 of 300
📘 CLASS XI
Which of the following features can be used logically to distinguish a young stem from a root under field conditions?
Stems bear nodes and internodes, are positively phototropic, generally green when young, and can bear multicellular hairs and buds, which are features that distinguish them from roots.
Question 159 of 300
📘 CLASS XI
Why does an axillary bud have the potential to form either a branch or a flower?
Axillary buds develop in the axils of leaves at nodes. As vegetative meristem, they can develop into lateral vegetative branches, or under reproductive signals, differentiate into floral buds (since a flower is a modified shoot).
Question 160 of 300
📘 CLASS XI
A botanist observes a plant where the stem becomes woody and dark brown as it ages. What is the physiological advantage of this transition from a green young stem to a woody old stem?
Young stems are green and soft, but as they grow older, they often become woody and dark brown, which provides strong mechanical support to sustain the weight of the growing shoot system (leaves, branches, flowers, and fruits).
