Studying the intricacies of plant morphology and physiology isn’t just a task for botanists; it’s a journey into understanding the fundamental mechanisms that sustain life on our planet. Aspirants of the UPSC Prelims delve into this realm not merely to answer questions but to grasp the essence of how plants grow, adapt, and interact with their environment. From the delicate intricacies of leaf venation to the complex processes of photosynthesis, each topic in plant morphology and physiology opens a window into the remarkable world of botanical science. In the following exploration of UPSC Prelims Topic Wise Questions on Biology – Plant Morphology and Physiology, we embark on a voyage through the verdant landscapes of plant life, where every stem, leaf, and flower tells a story of resilience and adaptation.
Q1. Most of the desert plants bloom during night time because [1995]
(a) their blooming is controlled by low temperature
(b) they are sensitive to the phases of moon
(c) the desert insect eat away flowers during day time
(d) the desert insects are active during night time
Ans. (d)
Many desert plants bloom at night to coincide with the activity of desert insects, which are primarily active during nocturnal hours. In desert environments, where daytime temperatures soar, the majority of plant and animal activity occurs under the cover of darkness. Desert insects emerge during these cooler hours to forage for food, prompting desert plants to synchronize their blooming patterns accordingly. By blossoming at night, these plants attract insects for pollination, ensuring their reproductive success in the harsh desert ecosystem.
Q2. Coffee cultivation in Sri Lanka was abandoned because of the disease (1995)
(a) leaf blight
(b) leaf spot
(c) leaf rust
(d) rot
Ans. (c)
Coffee cultivation in Sri Lanka came to a halt due to the devastating impact of leaf rust disease, caused by the fungus Hemileia vastatrix. This disease primarily targets the leaves and fruits of coffee plants. Additionally, another threat to coffee crops is bacterial leaf blight, attributed to Pseudomonas sytingae, which results in blight on both leaves and twigs. This affliction has been documented in regions across East Africa and South America.
Q3. It is possible to produce seedless tomato fruits by (1996)
(a) applying trace elements in tomato fields
(b) spraying mineral solution on plants
(c) spraying hormones on flowers
(d) applying fertilisers containing radioactive elements
Ans. (c)
Seedless tomato fruits can be achieved through the application of hormones onto flowers. These hormones, categorized as plant growth regulators, play a pivotal role in regulating plant growth and development. Among these regulators are auxins such as IAA and IBA, alongside gibberellins, which specifically govern fruit growth and development. Remarkably, gibberellins have the capacity to prompt the development of seedless fruits from unfertilized flowers. Unlike trace elements, fertilizers, and mineral solutions, which are vital for overall plant growth, they are incapable of producing seedless tomato fruits.
Q4. Which one of the following is a modified stem?(1996)
(a) Carrot
(b) Sweet potato
(c) Coconut
(d) Potato
Ans. (d)
Among the options provided, the potato (Solanum tuberosum) stands out as a modified stem. Its distinctive modification, known as a tuber, manifests as a swollen underground structure dedicated to storing food materials. Unlike typical stems, this non-green part serves as a reservoir for nutrients. Carrots and sweet potatoes, on the other hand, belong to the category of modified roots, serving a similar purpose of storing food. As for the coconut, it’s classified as a drupe, characterized by a stony fruit enclosing a filling of white, oily, and watery fluid called endosperm.
Q5. Which one of the following is not an essential micronutrient for plants?
(a) Boron
(b) Zinc
(c) Sodium
(d) Copper
Ans. (c)
Sodium is not considered a vital micronutrient for plant life. Micronutrients, also known as trace elements, are crucial mineral elements necessary in small amounts for optimal plant growth and development. These micronutrients include iron (Fe), manganese (Mn), boron (B), copper (Cu), zinc (Zn), molybdenum (Mo), and chlorine (Cl). Recently, nickel (Ni) has been recognized as a micronutrient. However, sodium (Na) is not essential for the growth and development of most plants, except for halophytes, which thrive in saline environments.
Q6. Ergotism is due to consumption of
(a) contaminated grains
(b) rotting vegetables
(c) contaminated water
(d) stale cooked food
Ans. (a)
Ergotism arises from the consumption of grains tainted by a fungal pathogen known as Claviceps purpurea. This form of poisoning occurs when grains like wheat, oats, rye, and millet are infected, leading to the release of ‘Ergotin’, a harmful substance responsible for inducing ergotism.
Q7. In a bisexual flower, if androecium and gynoecium mature at different times, the phenomenon is known as (2002)
(a) dichogamy
(b) herkogamy
(c) heterogamy
(d) monogamy
Ans. (a)
In a bisexual flower, when the male (androecium) and female (gynoecium) reproductive parts mature at different times, it’s termed dichogamy. This occurrence is prevalent among higher plants, serving to prevent self-fertilization or autogamy. Dichogamy manifests in two forms: Protandry, where the anther matures first, and protogyny, where the gynoecium matures first.
Q8. Consider the following plants (2002)
1. Bougainvillea
2. Carnations
3. Cocoa
4. Grapes
Which of these plants are propagated by stem cuttings?
(a) 1 and 2
(c) 1,3 and 4
(b) 2, 3 and 4
(d) 1, 2, 3 and 4
Ans. (d)
All four plants—Bougainvillea, cocoa, carnations, and grapes—are propagated through the stem cutting technique, a widely practiced method in plant propagation. This process involves cutting 20-30 cm long segments from one-year-old stems. These segments are then immersed in root-promoting hormones for several minutes before being planted in the soil. Other examples of plants propagated using this method include rose, sugarcane, citrus, and more.
Q9. Epiphytes are plants which depend upon other plants for (2002)
(A) food
(b) mechanical support
(c) shade
(d) water
Ans. (b)
Epiphytes are botanical wonders reliant on other plants for structural support. While they are self-sufficient in generating their own food through photosynthesis, their stems lack the robust strengthening tissues found in other plants, rendering them relatively frail.
Q10. Which one of the following parts of the pitcher plant becomes modified into a pitcher? (2007)
(a) Stem
(b) Leaf
(c) Stipule
(d) Petiole
Ans. (b)
The leaves of the pitcher plant undergo a unique modification, forming into pitchers. Insectivorous plants such as the pitcher plant, bladderwort, and sundew, exhibit specialized leaves designed to capture insects. These plants’ leaves ensnare, retain, and digest insects and other small creatures. Carnivorous plants are primarily found in bogs, sandy regions, and tropical rainforests.
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