The theory of 'Munch Hypothesis' explains the mechanism of: MCQ with Answer and Explanation

The theory of 'Munch Hypothesis' explains the mechanism of:
A. Transpiration pull
B. Translocation of food in phloem
C. Ascent of sap
D. Guttation
Answer: Option B
Solution (By JKExamLibrary)
The Munch hypothesis, or mass flow hypothesis, explains the translocation of organic solutes (primarily sucrose) through the phloem. It proposes that the movement is driven by a turgor pressure gradient between the source (where sugars are loaded into the phloem, increasing osmotic pressure) and the sink (where sugars are unloaded, decreasing osmotic pressure). Water flows from xylem to phloem and back, driving the bulk flow.

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Question #1
The 'Hormone Leptin' acts on the hypothalamus to regulate energy balance. It does this primarily by binding to receptors in the:
A. Suprachiasmatic nucleus
B. Ventromedial hypothalamus
C. Lateral hypothalamus
D. Arcuate nucleus

Correct Answer: Option D


Explanation:
Leptin is a hormone secreted by adipose tissue that signals the status of body fat stores to the brain. It acts primarily on the arcuate nucleus (ARC) of the hypothalamus. The ARC contains two key populations of neurons: one that co-expresses Neuropeptide Y (NPY) and Agouti-related peptide (AgRP), which stimulate appetite, and another that expresses Pro-opiomelanocortin (POMC) and Cocaine- and amphetamine-regulated transcript (CART), which suppress appetite. Leptin binds to receptors on these neurons, inhibiting the NPY/AgRP neurons and stimulating the POMC/CART neurons, thereby reducing appetite and increasing energy expenditure.

This question belongs to: Science Biology
Question #2
In plant physiology, the 'Root pressure' is a positive pressure that develops in the roots due to the active absorption of minerals and the subsequent osmotic entry of water. It is most evident during:
A. Early morning or night when transpiration is low and soil moisture is high
B. Winter when the ground is frozen
C. Mid-day when transpiration is high
D. Drought conditions

Correct Answer: Option A


Explanation:
Root pressure is a positive hydrostatic pressure generated in the xylem of roots due to the active secretion of ions into the xylem, which lowers the water potential and causes water to enter osmotically from the soil. This pressure can push water up the stem. Root pressure is most evident and measurable during the early morning or at night, when the rate of transpiration from the leaves is very low (or zero) and the soil moisture is high, allowing for maximum water absorption. It is responsible for phenomena like guttation and the exudation of sap from cut stems.

This question belongs to: Science Biology
Question #3
In the human eye, the image is formed on the:
A. Retina
B. Lens
C. Cornea
D. Optic nerve

Correct Answer: Option A


Explanation:
The retina is the light-sensitive inner layer of the eye containing photoreceptors (rods and cones) where an inverted real image is formed. The cornea and lens focus light onto the retina. The optic nerve transmits impulses from the retina to the brain for interpretation. The fovea centralis is the point of sharpest vision.

This question belongs to: Science Biology