Plant Physiology & Botany — Part 1: 40 MCQs with Explanations

Transpiration is the evaporation of water from plant leaves, mainly through stomata.

During the light reactions, water is split (photolysis) to release oxygen.

After fertilization, the ovule develops into the seed, and the ovary becomes the fruit.

Sunflowers, like most dicots, have a taproot system, while monocots like wheat have fibrous roots.

Stomata are pores, usually on the underside of leaves, that allow gas exchange.

The testa (seed coat) protects the inner embryo from damage and dehydration.

The MDCAT Biology syllabus includes carnivorous plants such as the pitcher plant, Venus flytrap, and sundew under the topic of life processes in plants.

The syllabus on life processes in plants specifies that xylem tissue is responsible for the transport of water and minerals from the roots to the rest of the plant.

Carotenoids are accessory pigments that absorb light energy and transfer it to chlorophyll. They also protect chlorophyll from photo-oxidation.

Iron is a micronutrient (trace element) needed in smaller amounts, whereas N, P, and K are primary macronutrients.

Using isotopic labeling (18O), it was demonstrated that the oxygen released during the light reactions comes from the photolysis of water (H2O).

After fertilization, the ovary of the flower typically develops into the fruit, while the ovules become the seeds.

The transpiration pull, created by the evaporation of water from leaves, is the main force that pulls water up the xylem vessels.

Transpiration is the evaporation of water vapor from aerial parts of plants, primarily through stomata in leaves.

Transpiration is the loss of water vapor from plant surfaces, primarily through stomata in leaves, creating a transpiration pull for water movement.

Photosynthesis occurs in chloroplasts, where light energy is converted to chemical energy stored in glucose molecules.

Photosynthesis is a process performed only by autotrophs (plants, algae, some bacteria), not all living organisms. Metabolism, reproduction, and response to stimuli are universal characteristics of life.

Photosynthesis converts light energy to chemical energy stored in glucose: 6CO₂ + 6H₂O + light energy → C₆H₁₂O₆ + 6O₂.

Transpiration is the evaporation of water vapor primarily through stomata in leaves, creating transpiration pull for upward water movement in xylem.

Transpiration is the evaporation of water vapor primarily through stomata in leaves, creating transpiration pull for xylem sap ascent.

The ovary wall (pericarp) develops into the fruit, while ovules within the ovary develop into seeds.

Photosynthesis converts light energy to chemical energy: 6CO₂ + 6H₂O + light → C₆H₁₂O₆ + 6O₂. Respiration reverses this process.

Transpiration creates negative pressure (tension) in leaf xylem, pulling water upward from roots through cohesion-tension mechanism.

Chlorophyll a absorbs blue-violet (~430 nm) and red (~662 nm) light most strongly; green light is reflected, giving plants their color.

Root hairs are epidermal extensions that dramatically increase surface area for water and mineral absorption from soil.

Xylem vessels/tracheids transport water and dissolved minerals from roots to shoots via transpiration pull and root pressure.

Phloem sieve tubes transport sucrose, amino acids, and other organic compounds from sources (leaves) to sinks (roots, fruits) via pressure flow mechanism.

Light-dependent reactions produce ATP and NADPH using light energy; these power carbon fixation in Calvin cycle.

Root pressure (from osmotic water entry) pushes xylem sap upward, causing guttation (water droplets on leaf edges) in humid conditions.

Transpiration is the evaporation of water vapor primarily through stomata in leaves, creating transpiration pull for upward water movement in xylem.

Photosynthesis converts light energy to chemical energy: 6CO₂ + 6H₂O + light → C₆H₁₂O₆ + 6O₂.

Transpiration is the evaporation of water vapor from aerial plant parts, mainly through stomata, creating transpiration pull for water ascent.

Guttation occurs at night when root pressure forces water out through hydathodes at leaf margins, forming droplets.

Xylem conducts water and dissolved minerals from roots to aerial plant parts and provides mechanical support.

Geotropism (gravitropism): roots show positive geotropism (grow downward); stems show negative geotropism (grow upward).

Light-dependent reactions in thylakoids produce ATP and NADPH using light energy; these power Calvin cycle to make glucose.

Cohesion-tension theory (primary mechanism) explains transpiration pull; root pressure and capillarity contribute minimally especially in tall trees.

Phototropism: auxin redistribution causes differential growth on shaded side, bending stem toward light source.

Roots anchor plant, absorb water/minerals, and store food (e.g., carrots); photosynthesis occurs in green aerial parts containing chlorophyll.

Assimilation: plants absorb nitrates/ammonium and incorporate nitrogen into amino acids, proteins, and nucleic acids.

Linnaeus published the list of names of plants in 1753 .

Sessile flowers have No pedicles .

Stamens are not usually pendulous in plants pollinated by Insects .

Protein and amino acids is the correct answer to “The plant dye Henna imparts orangered colour to skin and hairs due to its reaction with which of the following”. Items of this type are drawn from the Plant Physiology & Botany — Part 1 syllabus of Pakistani competitive exams, where the fact is tested verbatim.

The vascular plants are termed as tracheophytes .

The plants which produce embryo but lack vascular tissues and seeds are placed in bryophytes .

Higher vascular plants are also called seed plants .

plants is the correct answer to “Xylem and phloem are conducting tissues found in ¦¦¦.”. Items of this type are drawn from the Plant Physiology & Botany — Part 1 syllabus of Pakistani competitive exams, where the fact is tested verbatim.

chloroplast is the correct answer to “Which of the following manufactures carbohydrates by the process of photosynthesis”. Items of this type are drawn from the Plant Physiology & Botany — Part 1 syllabus of Pakistani competitive exams, where the fact is tested verbatim.

Leaves is the correct answer to “Which of the following structure in plants body is called excretophores”. Items of this type are drawn from the Plant Physiology & Botany — Part 1 syllabus of Pakistani competitive exams, where the fact is tested verbatim.

H2O is the correct answer to “In plants, which of the following is a waste product produced both during photosynthesis and respiration”. Items of this type are drawn from the Plant Physiology & Botany — Part 1 syllabus of Pakistani competitive exams, where the fact is tested verbatim.

O2 is the correct answer to “Which excretory product in produced in plants during autotrophic mode of life”. Items of this type are drawn from the Plant Physiology & Botany — Part 1 syllabus of Pakistani competitive exams, where the fact is tested verbatim.

Formation of heat shock proteins in plants results in Embracing the enzymes and other proteins and prevent their denaturation. .

Low level of CO2 favours Opening of the stomata.

Fungi is the correct answer to “Symbionts which help plants in uptake of phosphorous and trace metals such as zinc and copper.”. Items of this type are drawn from the Plant Physiology & Botany — Part 1 syllabus of Pakistani competitive exams, where the fact is tested verbatim.

The opening and closing of stomata is directly controlled by the Light .

There are Two hypothesis which may explain opening and closing of stomata.

Pulling upward of water and dissolved minerals towards the leaves through the xylem tissue is called Transpiration pull .

Stomatal transpiration is 90% of total transpiration.

All plants do not possess Lenticels .

Lenticular transpiration is 1-2% of total transpiration.

Commonly in other plants than tall ones the speed of upward movement of water is 1 mh-1 .

Exceptionally the positive hydrostatic pressure generated by root pressure is about 800 Kpa .

Cuticular transpiration is 5-7% of total transpiration.

Two is the correct answer to “In plants, water potential is determined by major factors”. Items of this type are drawn from the Plant Physiology & Botany — Part 1 syllabus of Pakistani competitive exams, where the fact is tested verbatim.

There are Three types of nutrients needed by plants besides light to carry out photosynthesis.

The uptake of water in plants involves Passive transport .

Roots of a plant show Negative phototropism and positive geotropism .

The place of attachment of leaf with the shoot is called Pulvinus .

An increrase in plant girth due to activity of Both a and c is called secondary growth.

Calvin cycle is the correct answer to “Which of the following promotes growth in plants”. Items of this type are drawn from the Plant Physiology & Botany — Part 1 syllabus of Pakistani competitive exams, where the fact is tested verbatim.

There are 100,000 stomata per square cm of leaf surface in Tobacco plants.

The air spaces may comprise upto 40% of total volume of leaf surface.

Chlorophylls mainly absorb Orange red. wavelengths.

Deficiency of Magnesium causes yellowing in plants.

In all plants the major sites of phosynthesis are Leaves respire and utilize O2 and release CO2. .

Molecular formula of chlorophyll a molecule is C55H72O5N4Mg .

Stomata cover only 1-2 % of leaf surface.

Reduction in photosynthesis is of CO2 .

Both A and B is the correct answer to “Which of the light is mainly absorbed by the plants”. Items of this type are drawn from the Plant Physiology & Botany — Part 1 syllabus of Pakistani competitive exams, where the fact is tested verbatim.