Plant Biology and Photosynthesis MCQs 2026

Phloem tissue mainly conducts

1. A Water only ✓
2. B Minerals only ✓
3. C Organic food (sugars) ✓
4. D Oxygen ✓

Translocation of sugars (organic food) in phloem occurs mainly according to the

1. A Cohesion-tension theory ✓
2. B Osmotic theory of water absorption ✓
3. C Root pressure theory ✓
4. D Pressure-flow (mass flow) hypothesis ✓

Guard cells regulate the opening and closing of

1. A Lenticels ✓
2. B Stomata ✓
3. C Root hairs ✓
4. D Xylem vessels ✓

Stomata typically open when guard cells become

1. A Flaccid ✓
2. B Plasmolyzed ✓
3. C Turgid ✓
4. D Dehydrated ✓

The green pigment primarily responsible for absorbing light energy in photosynthesis is

1. A Chlorophyll a ✓
2. B Carotene ✓
3. C Xanthophyll ✓
4. D Anthocyanin ✓

Phosphorus deficiency in plants is commonly indicated by

1. A Yellowing of young leaves ✓
2. B Purplish discoloration of leaves and poor root development ✓
3. C Wilting of stems only ✓
4. D Excess fruit production ✓

Photoperiodism refers to a plant's response to

1. A Relative length of day and night ✓
2. B Soil pH ✓
3. C Temperature fluctuations only ✓
4. D Wind direction ✓

Plants that flower only when day length exceeds a critical value are called

1. A Long-day plants ✓
2. B Short-day plants ✓
3. C Day-neutral plants ✓
4. D CAM plants ✓

The pigment involved in detecting photoperiod and regulating flowering in plants is

1. A Chlorophyll b ✓
2. B Carotenoid ✓
3. C Phytochrome ✓
4. D Anthocyanin ✓

During cellular respiration in plants, glucose is broken down in the presence of oxygen to release

1. A Only heat ✓
2. B Only water ✓
3. C Only glucose ✓
4. D Energy (ATP), carbon dioxide and water ✓

Which best describes the relationship between photosynthesis and respiration in green plants during daylight

1. A Only respiration occurs ✓
2. B Only photosynthesis occurs ✓
3. C Both processes occur simultaneously ✓
4. D Neither process occurs ✓

The compensation point in plants refers to the light intensity at which

1. A Photosynthesis stops completely ✓
2. B Rate of photosynthesis equals rate of respiration ✓
3. C Respiration stops completely ✓
4. D Transpiration is maximum ✓

Seed germination in which cotyledons are pushed above the soil surface is called

1. A Epigeal germination ✓
2. B Hypogeal germination ✓
3. C Vivipary ✓
4. D Vegetative propagation ✓

In hypogeal germination, the cotyledons remain

1. A Above the soil, turning green ✓
2. B Detached from the seed ✓
3. C Converted into flowers ✓
4. D Below the soil surface ✓

Vegetative propagation in plants such as potato tubers and ginger rhizomes is an example of

1. A Sexual reproduction ✓
2. B Spore formation ✓
3. C Pollination ✓
4. D Asexual (clonal) reproduction ✓

Parenchyma tissue in plants is primarily associated with

1. A Mechanical strength only ✓
2. B Storage, photosynthesis and packing ✓
3. C Water conduction only ✓
4. D Reproduction ✓

Sclerenchyma cells provide rigidity to mature plant parts mainly due to

1. A Thick lignified cell walls ✓
2. B High water content ✓
3. C Living protoplasm ✓
4. D Chlorophyll presence ✓

The bark of a tree is composed mainly of

1. A Xylem tissue ✓
2. B Cork and phloem tissue outside the cambium ✓
3. C Pith ✓
4. D Root hairs ✓

Lenticels in woody stems primarily function for

1. A Water absorption ✓
2. B Gas exchange through the bark ✓
3. C Food storage ✓
4. D Light absorption ✓

The primary source of carbon used by plants in photosynthesis is

1. A Carbonates in soil ✓
2. B Nitrogen gas ✓
3. C Atmospheric carbon dioxide ✓
4. D Organic matter in humus ✓

The light-dependent reactions of photosynthesis occur in the

1. A Stroma ✓
2. B Thylakoid membrane ✓
3. C Cytoplasm ✓
4. D Mitochondrial matrix ✓

The light-independent reactions (Calvin cycle) of photosynthesis take place in the

1. A Thylakoid lumen ✓
2. B Stroma ✓
3. C Grana ✓
4. D Outer chloroplast membrane ✓

During photosynthesis, the splitting of water molecules (photolysis) releases

1. A Carbon dioxide ✓
2. B Glucose ✓
3. C Oxygen ✓
4. D Nitrogen ✓

The primary CO2-fixing enzyme in C3 plants is

1. A PEP carboxylase ✓
2. B RuBisCO ✓
3. C ATP synthase ✓
4. D Carbonic anhydrase ✓

A plant deficient in nitrogen typically shows

1. A Chlorosis (yellowing) of older leaves ✓
2. B Purple discoloration of leaves ✓
3. C Stunted root growth only ✓
4. D Excessive flowering ✓

C4 plants are more efficient than C3 plants in hot, dry climates mainly because they

1. A Lack stomata ✓
2. B Perform photosynthesis only at night ✓
3. C Minimize photorespiration via PEP carboxylase ✓
4. D Do not require sunlight ✓

An example of a C4 plant is

1. A Wheat ✓
2. B Rice ✓
3. C Maize (corn) ✓
4. D Potato ✓

CAM plants, adapted to arid environments, mainly open their stomata during the

1. A Night ✓
2. B Midday ✓
3. C Early morning only ✓
4. D They never close stomata ✓

The overall equation of photosynthesis produces glucose and

1. A Carbon dioxide ✓
2. B Nitrogen ✓
3. C Oxygen ✓
4. D Ozone ✓

Which plant hormone is primarily responsible for cell elongation and phototropism

1. A Cytokinin ✓
2. B Ethylene ✓
3. C Abscisic acid ✓
4. D Auxin ✓

Gibberellins are well known for promoting

1. A Leaf abscission ✓
2. B Stem elongation and seed germination ✓
3. C Fruit ripening ✓
4. D Stomatal closure ✓

Abscisic acid (ABA) is often called the stress hormone because it

1. A Promotes rapid cell division ✓
2. B Speeds up fruit ripening ✓
3. C Induces stomatal closure under water stress ✓
4. D Stimulates flowering ✓

Ethylene gas is primarily responsible for

1. A Root growth ✓
2. B Seed dormancy ✓
3. C Cell division in the shoot apex ✓
4. D Fruit ripening ✓

Cytokinins are plant hormones that primarily promote

1. A Stomatal closure ✓
2. B Leaf senescence ✓
3. C Dormancy ✓
4. D Cell division ✓

The bending of a plant shoot toward a light source is termed

1. A Geotropism ✓
2. B Hydrotropism ✓
3. C Phototropism ✓
4. D Thigmotropism ✓

Root growth toward the pull of gravity is an example of

1. A Positive geotropism ✓
2. B Negative geotropism ✓
3. C Positive phototropism ✓
4. D Chemotropism ✓

The coiling response of a climbing plant tendril upon touching a support is called

1. A Phototropism ✓
2. B Geotropism ✓
3. C Hydrotropism ✓
4. D Thigmotropism ✓

The vascular cambium is responsible for

1. A Secondary growth (increase in girth) ✓
2. B Primary growth in length ✓
3. C Photosynthesis ✓
4. D Water absorption ✓

Mineral nutrients such as nitrogen are essential to plants mainly to synthesize

1. A Cellulose only ✓
2. B Starch only ✓
3. C Fats only ✓
4. D Proteins, chlorophyll and nucleic acids ✓

In dicot stems, xylem and phloem vascular bundles are typically arranged

1. A Scattered throughout the stem ✓
2. B In a ring, conjoint and collateral with cambium ✓
3. C Absent ✓
4. D Only in roots ✓

Monocot leaves typically show a venation pattern that is

1. A Reticulate ✓
2. B Parallel ✓
3. C Palmate ✓
4. D Absent ✓

Which of the following distinguishes dicot from monocot seeds

1. A Presence of endosperm only in dicots ✓
2. B Absence of embryo in monocots ✓
3. C Two cotyledons in dicots versus one in monocots ✓
4. D Monocots always lack a seed coat ✓

Root hairs increase the surface area mainly for

1. A Absorption of water and minerals ✓
2. B Photosynthesis ✓
3. C Gas exchange only ✓
4. D Storage of starch ✓

The movement of water from soil into root hair cells occurs mainly by

1. A Active transport ✓
2. B Diffusion of gases ✓
3. C Facilitated transport of ions only ✓
4. D Osmosis ✓

Transpiration serves plants primarily by

1. A Producing food ✓
2. B Releasing oxygen only ✓
3. C Preventing photosynthesis ✓
4. D Cooling the plant and pulling water upward ✓

Guttation, the exudation of water droplets from leaf margins, occurs mainly due to

1. A Root pressure ✓
2. B High transpiration rate ✓
3. C Low humidity ✓
4. D Excess sunlight ✓

The apical meristem responsible for primary growth is located at

1. A Nodes of the stem ✓
2. B Tips of roots and shoots ✓
3. C Cortex of the root ✓
4. D Vascular cambium ✓

Which tissue provides mechanical support to young, growing plant parts due to unevenly thickened cell walls

1. A Parenchyma ✓
2. B Sclerenchyma ✓
3. C Xylem ✓
4. D Collenchyma ✓

Which tissue is responsible for conducting water and minerals from roots to leaves

1. A Xylem ✓
2. B Phloem ✓
3. C Cambium ✓
4. D Epidermis ✓

The upward movement of water in xylem driven by loss of water vapor from leaves is called

1. A Transpiration pull ✓
2. B Root pressure ✓
3. C Osmosis ✓
4. D Guttation ✓