Plant Biology and Photosynthesis MCQs 2026

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

1. AChlorophyll a✓
2. BCarotene✓
3. CXanthophyll✓
4. DAnthocyanin✓

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

1. APromotes rapid cell division✓
2. BSpeeds up fruit ripening✓
3. CInduces stomatal closure under water stress✓
4. DStimulates flowering✓

The overall equation of photosynthesis produces glucose and

1. ACarbon dioxide✓
2. BNitrogen✓
3. COxygen✓
4. DOzone✓

Phloem tissue mainly conducts

1. AWater only✓
2. BMinerals only✓
3. COrganic food (sugars)✓
4. DOxygen✓

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

1. ATranspiration pull✓
2. BRoot pressure✓
3. COsmosis✓
4. DGuttation✓

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

1. AXylem✓
2. BPhloem✓
3. CCambium✓
4. DEpidermis✓

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

1. AParenchyma✓
2. BSclerenchyma✓
3. CXylem✓
4. DCollenchyma✓

Ethylene gas is primarily responsible for

1. ARoot growth✓
2. BSeed dormancy✓
3. CCell division in the shoot apex✓
4. DFruit ripening✓

Cytokinins are plant hormones that primarily promote

1. AStomatal closure✓
2. BLeaf senescence✓
3. CDormancy✓
4. DCell division✓

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

1. AGeotropism✓
2. BHydrotropism✓
3. CPhototropism✓
4. DThigmotropism✓

Root growth toward the pull of gravity is an example of

1. APositive geotropism✓
2. BNegative geotropism✓
3. CPositive phototropism✓
4. DChemotropism✓

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

1. APhototropism✓
2. BGeotropism✓
3. CHydrotropism✓
4. DThigmotropism✓

The vascular cambium is responsible for

1. ASecondary growth (increase in girth)✓
2. BPrimary growth in length✓
3. CPhotosynthesis✓
4. DWater absorption✓

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

1. AScattered throughout the stem✓
2. BIn a ring, conjoint and collateral with cambium✓
3. CAbsent✓
4. DOnly in roots✓

Monocot leaves typically show a venation pattern that is

1. AReticulate✓
2. BParallel✓
3. CPalmate✓
4. DAbsent✓

Which of the following distinguishes dicot from monocot seeds

1. APresence of endosperm only in dicots✓
2. BAbsence of embryo in monocots✓
3. CTwo cotyledons in dicots versus one in monocots✓
4. DMonocots always lack a seed coat✓

Root hairs increase the surface area mainly for

1. AAbsorption of water and minerals✓
2. BPhotosynthesis✓
3. CGas exchange only✓
4. DStorage of starch✓

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

1. AActive transport✓
2. BDiffusion of gases✓
3. CFacilitated transport of ions only✓
4. DOsmosis✓

Transpiration serves plants primarily by

1. AProducing food✓
2. BReleasing oxygen only✓
3. CPreventing photosynthesis✓
4. DCooling the plant and pulling water upward✓

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

1. ARoot pressure✓
2. BHigh transpiration rate✓
3. CLow humidity✓
4. DExcess sunlight✓

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

1. ACohesion-tension theory✓
2. BOsmotic theory of water absorption✓
3. CRoot pressure theory✓
4. DPressure-flow (mass flow) hypothesis✓

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

1. ACellulose only✓
2. BStarch only✓
3. CFats only✓
4. DProteins, chlorophyll and nucleic acids✓

A plant deficient in nitrogen typically shows

1. AChlorosis (yellowing) of older leaves✓
2. BPurple discoloration of leaves✓
3. CStunted root growth only✓
4. DExcessive flowering✓

Phosphorus deficiency in plants is commonly indicated by

1. AYellowing of young leaves✓
2. BPurplish discoloration of leaves and poor root development✓
3. CWilting of stems only✓
4. DExcess fruit production✓

Photoperiodism refers to a plant's response to

1. ARelative length of day and night✓
2. BSoil pH✓
3. CTemperature fluctuations only✓
4. DWind direction✓

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

1. ALong-day plants✓
2. BShort-day plants✓
3. CDay-neutral plants✓
4. DCAM plants✓

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

1. AChlorophyll b✓
2. BCarotenoid✓
3. CPhytochrome✓
4. DAnthocyanin✓

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

1. AOnly heat✓
2. BOnly water✓
3. COnly glucose✓
4. DEnergy (ATP), carbon dioxide and water✓

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

1. AOnly respiration occurs✓
2. BOnly photosynthesis occurs✓
3. CBoth processes occur simultaneously✓
4. DNeither process occurs✓

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

1. APhotosynthesis stops completely✓
2. BRate of photosynthesis equals rate of respiration✓
3. CRespiration stops completely✓
4. DTranspiration is maximum✓

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

1. AEpigeal germination✓
2. BHypogeal germination✓
3. CVivipary✓
4. DVegetative propagation✓

In hypogeal germination, the cotyledons remain

1. AAbove the soil, turning green✓
2. BDetached from the seed✓
3. CConverted into flowers✓
4. DBelow the soil surface✓

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

1. ASexual reproduction✓
2. BSpore formation✓
3. CPollination✓
4. DAsexual (clonal) reproduction✓

Parenchyma tissue in plants is primarily associated with

1. AMechanical strength only✓
2. BStorage, photosynthesis and packing✓
3. CWater conduction only✓
4. DReproduction✓

Sclerenchyma cells provide rigidity to mature plant parts mainly due to

1. AThick lignified cell walls✓
2. BHigh water content✓
3. CLiving protoplasm✓
4. DChlorophyll presence✓

The bark of a tree is composed mainly of

1. AXylem tissue✓
2. BCork and phloem tissue outside the cambium✓
3. CPith✓
4. DRoot hairs✓

Lenticels in woody stems primarily function for

1. AWater absorption✓
2. BGas exchange through the bark✓
3. CFood storage✓
4. DLight absorption✓

The primary source of carbon used by plants in photosynthesis is

1. ACarbonates in soil✓
2. BNitrogen gas✓
3. CAtmospheric carbon dioxide✓
4. DOrganic matter in humus✓

The apical meristem responsible for primary growth is located at

1. ANodes of the stem✓
2. BTips of roots and shoots✓
3. CCortex of the root✓
4. DVascular cambium✓

Which plant hormone is primarily responsible for cell elongation and phototropism

1. ACytokinin✓
2. BEthylene✓
3. CAbscisic acid✓
4. DAuxin✓

The light-dependent reactions of photosynthesis occur in the

1. AStroma✓
2. BThylakoid membrane✓
3. CCytoplasm✓
4. DMitochondrial matrix✓

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

1. AThylakoid lumen✓
2. BStroma✓
3. CGrana✓
4. DOuter chloroplast membrane✓

Gibberellins are well known for promoting

1. ALeaf abscission✓
2. BStem elongation and seed germination✓
3. CFruit ripening✓
4. DStomatal closure✓

Guard cells regulate the opening and closing of

1. ALenticels✓
2. BStomata✓
3. CRoot hairs✓
4. DXylem vessels✓

Stomata typically open when guard cells become

1. AFlaccid✓
2. BPlasmolyzed✓
3. CTurgid✓
4. DDehydrated✓

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

1. ACarbon dioxide✓
2. BGlucose✓
3. COxygen✓
4. DNitrogen✓

The primary CO2-fixing enzyme in C3 plants is

1. APEP carboxylase✓
2. BRuBisCO✓
3. CATP synthase✓
4. DCarbonic anhydrase✓

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

1. ALack stomata✓
2. BPerform photosynthesis only at night✓
3. CMinimize photorespiration via PEP carboxylase✓
4. DDo not require sunlight✓

An example of a C4 plant is

1. AWheat✓
2. BRice✓
3. CMaize (corn)✓
4. DPotato✓

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

1. ANight✓
2. BMidday✓
3. CEarly morning only✓
4. DThey never close stomata✓