Q31. Which nutrient is vital for photosynthesis as a component of chlorophyll?
a) Nitrogen
b) Phosphorus
c) Magnesium
d) Potassium
Show Answer
Correct Answer: c) Magnesium
Explanation: Magnesium is vital for photosynthesis as it is a central component of the chlorophyll molecule. Chlorophyll is the pigment that absorbs sunlight, enabling the photosynthesis process. Without magnesium, plants cannot produce chlorophyll and thus are unable to perform photosynthesis efficiently.
Q32. What is the main reason for pruning plant roots in horticulture?
a) To reduce the size of the plant
b) To encourage root branching and denser growth
c) To eliminate root diseases
d) To prepare plants for transplantation
Show Answer
Correct Answer: b) To encourage root branching and denser growth
Explanation: The main reason for pruning plant roots in horticulture is to encourage root branching and denser growth. This practice stimulates the plant to produce new root growth, which can lead to a healthier and more vigorous plant. Denser root systems can improve nutrient and water uptake, enhancing overall plant growth and productivity.
Q33. In plants, what are auxins primarily responsible for?
a) Enhancing flower color
b) Regulating growth and tropic responses
c) Protecting against diseases
d) Accelerating seed germination
Show Answer
Correct Answer: b) Regulating growth and tropic responses
Explanation: Auxins are a group of plant hormones primarily responsible for regulating growth and tropic responses, such as phototropism (growth towards light) and gravitropism (growth in response to gravity). They play a key role in cell elongation, root formation, and branching, as well as in the development of fruit.
Q34. What mechanism do desert plants primarily use to conserve water?
a) Shallow and widespread roots
b) Reduced leaf size or absence of leaves
c) Enhanced photosynthetic rate
d) High stomatal density
Show Answer
Correct Answer: b) Reduced leaf size or absence of leaves
Explanation: Desert plants often conserve water by reducing leaf size or having no leaves at all. Instead, they may use their stems for photosynthesis. This adaptation reduces the surface area for transpiration, the process of water loss from plants. Some desert plants also have specialized features like thick, waxy skins to reduce water loss further.
Q35. What role do leguminous plants play in agriculture?
a) They increase soil nitrogen through nitrogen fixation.
b) They are primarily used as cover crops to reduce erosion.
c) They enhance soil phosphorus availability.
d) They act as natural pesticides by repelling insects.
Show Answer
Correct Answer: a) They increase soil nitrogen through nitrogen fixation.
Explanation: Leguminous plants, such as peas and beans, play a crucial role in agriculture by increasing soil nitrogen through the process of nitrogen fixation. They form symbiotic relationships with Rhizobium bacteria in their root nodules, which convert atmospheric nitrogen into a form that the plants can use. This process enriches the soil with nitrogen, reducing the need for synthetic fertilizers.
Q36. What is the role of potassium in plant nutrition?
a) Enhancing root development
b) Assisting in photosynthesis
c) Improving disease resistance
d) Regulating stomatal opening and closing
Show Answer
Correct Answer: d) Regulating stomatal opening and closing
Explanation: Potassium plays a critical role in plant nutrition by regulating the opening and closing of stomata, which are small pores on the leaf surface. Through this regulation, potassium helps control the exchange of gases and the loss of water vapor, maintaining the plant’s water balance. It also influences various processes such as enzyme activation, photosynthesis, and nutrient transport.
Q37. In which part of the plant does the process of pollination occur?
a) Leaves
b) Stems
c) Roots
d) Flowers
Show Answer
Correct Answer: d) Flowers
Explanation: Pollination occurs in the flowers of a plant. It involves the transfer of pollen from the male part of the flower (the stamen) to the female part (the pistil). This process can occur within the same flower, between flowers of the same plant, or between flowers of different plants, and is often aided by wind, water, or animals.
Q38. What adaptation do epiphytic plants have for their mode of nutrition?
a) Specialized roots for penetrating host tissues
b) Leaves modified for catching insects
c) Ability to absorb moisture and nutrients from the air
d) Enhanced root systems for extracting soil nutrients
Show Answer
Correct Answer: c) Ability to absorb moisture and nutrients from the air
Explanation: Epiphytic plants have adaptations that allow them to absorb moisture and nutrients from the air. They often grow on other plants for physical support and not for nutrition, relying on the surrounding environment for their nutritional needs. They have specialized root systems and other structures to capture water and nutrients from rain, air, or debris accumulating around them.
Q39. Which part of a plant is typically involved in climbing or supporting mechanisms?
a) Stolon
b) Rhizome
c) Tendril
d) Tubers
Show Answer
Correct Answer: c) Tendril
Explanation: Tendrils are typically involved in climbing or supporting mechanisms in plants. These slender, thread-like structures coil around supports, helping plants like peas and grapes to climb and gain access to more sunlight. Tendrils can originate from various parts of the plant, including stems, leaves, or even inflorescences.
Q40. How do insectivorous plants like pitcher plants obtain nutrients?
a) Through photosynthesis
b) By capturing and digesting insects
c) From the soil
d) Through symbiotic relationships
Show Answer
Correct Answer: b) By capturing and digesting insects
Explanation: Insectivorous plants like pitcher plants obtain nutrients by capturing and digesting insects. These plants have modified leaves forming a deep cavity filled with digestive liquid. Insects attracted to the plant for various reasons (such as nectar or color) fall into the cavity and are digested by the enzymes or bacteria present. This adaptation is especially beneficial in nutrient-poor soils, where these plants often grow.