Science Group
Explore subjects and practice MCQs
10
Chapters
1,000
Total MCQs
Unit-8 Plant Physiology
Answer: Plant physiology deals with how plants carry out vital life processes such as absorption, transport, photosynthesis and excretion.
Answer: Water enters root hairs by osmosis because the root hair cell sap is more concentrated than the soil water.
Answer: Xylem conducts water and dissolved minerals upward from the roots to the leaves.
Answer: Root hairs are extensions of root epidermal cells that greatly increase the surface area for absorption.
Answer: Transpiration is the loss of water vapour, mainly through the stomata of leaves.
Answer: Dixon and Joly proposed the cohesion-tension theory to explain the upward movement of water in xylem.
7
Answer: Cohesive forces between water molecules and adhesion to the xylem walls keep a continuous water column.
Answer: Most stomata are found in the lower epidermis of leaves where they allow gas exchange.
Answer: Carbon dioxide diffuses into the leaf through stomata and is used to make glucose in photosynthesis.
Answer: Evaporation from leaves creates tension; the pull is transmitted along the water column and water rises.
Answer: Phloem carries organic food by translocation from leaves to other plant parts.
Answer: Sieve tubes are living phloem cells that conduct sugars and other organic food.
Answer: Guttation occurs through hydathodes, which are special pores found at leaf margins.
Answer: When transpiration is low and root pressure is high, water is forced out as droplets through hydathodes.
Answer: Cohesive forces hold water molecules together, keeping the xylem water column continuous.
Answer: Lenticels are pores on woody stems and some roots that allow gaseous exchange.
Answer: The three types of transpiration are stomatal, cuticular and lenticular; xylary transpiration does not exist.
Answer: Stomatal transpiration accounts for roughly 90% of the water lost by a plant.
Answer: Photosynthesis combines carbon dioxide and water to make glucose while releasing oxygen.
Answer: Low humidity, high temperature, wind and light all increase the rate of transpiration.