NDA Biology · Formula sheet
Plant Biology formulas
2 formulas, 8 reference tables and 23 common traps for NDA Biology Plant Biology, grouped by subtopic.
Plant Tissues and Meristems
Learn this subtopic in the notesTypes of meristem — apical, lateral, intercalary
| Meristem | Where | Causes growth in |
|---|---|---|
| Apical | Root and shoot tips | Length / height (primary growth) Damage to the apical meristem reduces the LENGTH of the plant (NDA 2018). |
| Lateral (cambium) | Sides of the stem | Girth / thickness (secondary growth) Increase in girth of the stem is due to lateral meristem ONLY (NDA 2021). Cambium = a lateral meristem (NDA 2025). |
| Intercalary | Base of leaves / internodes | Length (regrowth, e.g. grasses) |
Memory hook: Apical = Altitude (height); Lateral = girth (wide). Cambium is lateral.
Simple permanent tissues — parenchyma, collenchyma, sclerenchyma
| Tissue | Living / dead | Role + key fact |
|---|---|---|
| Parenchyma | Living | Basic packing + storage; found in xylem and phloem; forms aerenchyma (air sacs) in aquatic plants Parenchyma is the 'basic packing tissue' found in xylem and phloem (NDA 2021); aerenchyma buoyancy sacs are parenchyma (NDA 2022). |
| Collenchyma | Living | Thickened walls give flexibility to the plant |
| Sclerenchyma | DEAD | Lignified walls; rigid support; no protoplast at maturity Sclerenchyma is the simple tissue made of DEAD cells (NDA 2020, 2026). |
Only sclerenchyma is dead. Parenchyma = packing/storage; collenchyma = flexibility.
Conducting tissues — xylem and phloem
| Tissue | Carries | Components |
|---|---|---|
| Xylem | Water + minerals | Tracheids, vessels, xylem parenchyma, xylem fibres Xylem = tracheids + vessels + xylem parenchyma + xylem fibres (NDA 2019). |
| Phloem | Food (sucrose) | Sieve tubes, sieve plates, companion cells, phloem parenchyma, fibres |
| Pericycle | NOT conducting | A parenchyma layer outside the vascular bundle — a distractor Pericycle is NOT a component of conducting tissue (NDA 2019). |
Tracheids/vessels = xylem; sieve tubes/companion cells = phloem; pericycle = neither.
Which organisms have vascular tissue
| Organism | Group | Vascular tissue? |
|---|---|---|
| Marsilea | Fern (pteridophyte) | YES — true xylem + phloem |
| Cladophora | Green alga | No |
| Penicillium | Fungus | No |
| Anabaena | Cyanobacterium | No |
Only the fern (Marsilea) has vascular tissue; algae, fungi and cyanobacteria do not.
Common traps
Apical = length, Lateral = girth — don't swap them
Apical meristems (tips) make the plant taller/longer; lateral meristems / cambium (sides) make it thicker (girth). The bank asks both directions — 'what increases girth?' (lateral) and 'damage to apical affects?' (length).
Differentiation ≠ division
Distractors offer cell division, multiplication, regeneration. The transformation of meristematic cells INTO permanent tissue is differentiation — division only makes more identical cells; differentiation gives them their permanent identity.
Sclerenchyma is the DEAD one
When asked which plant tissue is 'dead' or 'without protoplast', the answer is sclerenchyma (lignified walls). Parenchyma and collenchyma are both LIVING. Flexibility is collenchyma — not sclerenchyma.
Parenchyma hides inside the conducting tissues
Parenchyma is not just the soft filler — it occurs as xylem parenchyma and phloem parenchyma inside the conducting tissues, and as aerenchyma in aquatic plants. 'Basic packing tissue found in xylem and phloem' = parenchyma.
Pericycle is NOT a conducting component
Asked for the 'odd one out' that is NOT part of conducting tissue, the answer is the pericycle — fibres, tracheids and sieve tubes ARE conducting components; the pericycle is a parenchyma layer outside the vascular bundle.
Sieve plates and companion cells are PHLOEM, not xylem
A trap statement lists 'xylem consists of sieve plate, sieve tube and companion cells' — those are phloem components. Xylem = tracheids, vessels, xylem parenchyma, xylem fibres.
Spot the plant among the non-plants
Cladophora (alga), Penicillium (fungus) and Anabaena (cyanobacterium) are NOT vascular plants. Marsilea, a fern, is — it is the only one with true conducting tissue.
Photosynthesis
Learn this subtopic in the notesPhotosynthesis — requirements, equation and products
Overall photosynthesis equation
- carbon dioxide — the carbon source (a requirement)
- water — the hydrogen source (a requirement)
- glucose — the food made (a product)
- oxygen — released (a PRODUCT, never a requirement)
The light reaction — splitting water releases oxygen
Photolysis of water (the source of O₂)
- water — the molecule that is split
- oxygen released — sourced from water, not CO₂
Crop and botany facts — golden rice, sugarcane, cropping, nettle
| Fact | Answer | Note |
|---|---|---|
| Golden rice produces | Vitamin A (beta-carotene) | GM crop targeting vitamin-A deficiency Golden rice = Vitamin A, NOT omega-3 or vitamin B/C (NDA 2017). |
| Sugarcane is grown for | Sucrose | The cash-crop sugar; not glucose/fructose/starch |
| Two+ crops grown together | Intercropping | Same land, same time, defined rows Intercropping = simultaneous; crop rotation = in sequence (NDA 2020). |
| Nettle sting injects | Methanoic (formic) acid | Through hollow stinging hairs |
Stand-alone recall pairs — no shared mechanism, just memorise them.
Common traps
Oxygen is a PRODUCT, not a requirement
The 'which is NOT a requirement' question is a classic. Chlorophyll, CO₂ and water are all needed; oxygen is released, so it is the odd one out. Don't confuse the inputs with the outputs.
Only ~1% of sunlight is used
Green plants capture only about 1% of the solar radiation that hits them — distractors offer 5%, 8%, 10%. Most light is reflected or turned to heat.
Released O₂ comes from WATER, not CO₂
A favourite trap offers 'carbon dioxide' as the source of the oxygen. The oxygen evolved comes from splitting water (photolysis). CO₂ is reduced to sugar in the dark reaction — its oxygen is not the gas released.
Water splits in the LIGHT reaction
The correct statement is 'water molecule splits into hydrogen and oxygen'. The misleading distractor 'light energy is directly used to split water' overstates it — water splitting happens within the light-dependent machinery, not by light acting alone.
Leaves look green because chlorophyll REFLECTS green
A reversed distractor says chlorophyll 'absorbs green'. It is the opposite — chlorophyll absorbs red and blue and reflects green, and we see that reflected green.
Meristem is LIVING and dividing — not dead wood
Distractors call meristem 'dead tissue forming wood', 'flexibility tissue', or 'only in bark'. The correct statement is that growth occurs due to the division of meristematic cells — they are living, dividing cells at tips and the cambium.
Golden rice = Vitamin A
Golden rice is engineered for Vitamin A (beta-carotene), not omega-3 fatty acids or vitamins B/C. It targets vitamin-A deficiency.
Intercropping (simultaneous) vs crop rotation (sequential)
Intercropping = two or more crops at the SAME TIME on the same land. Crop rotation = different crops in SEQUENCE across seasons. Don't swap them.
Plant Processes — Gas Exchange, Transpiration and Tropisms
Learn this subtopic in the notesCommon traps
Photosynthesis + Oxygen is the linked pair
The question pairs a process with its gaseous product that another vital process needs. The right pair is photosynthesis and oxygen — not 'respiration and nitric oxide' or 'germination and CO₂'. Photosynthesis makes O₂; respiration uses it.
Shoot up = NEGATIVE geotropism (not negative phototropism)
A shoot's upward growth against gravity is negatively geotropic. The distractor 'negatively phototropic' is wrong — shoots are POSITIVELY phototropic (towards light). The upward-against-gravity fact is specifically negative geotropism.
Lower surface coated = dries up LAST
Because most dicot stomata are on the lower surface, sealing the LOWER surface cuts water loss the most, so that leaf dries up last. The trap is to pick the upper-coated leaf — but sealing the stomata-poor upper surface barely helps.
Seed, Fruit and Embryo Development
Learn this subtopic in the notesTrue vs false fruit, and the inflorescence
| Structure | What it is | Example |
|---|---|---|
| False fruit (apple) | Fleshy part from the thalamus, not the ovary | Apple, pear (pseudocarps) Apple's edible part = thalamus / receptacle (NDA 2026), not petal/sepal/stamen. |
| Inflorescence | A cluster of many florets on one axis | Sunflower, marigold (Asteraceae) The colourful sunflower/marigold 'flower' is an INFLORESCENCE (NDA 2017). |
Apple flesh = thalamus (false fruit); sunflower head = inflorescence (many florets).
Parts of the ovule — where reserve food is stored
| Ovule part | Role |
|---|---|
| Nucellus | Nutritive tissue holding the reserve food The ovule part with reserve food = nucellus (NDA 2026). |
| Integument | Outer protective layer (→ seed coat) |
| Funicle | Stalk attaching the ovule |
| Chalaza | Base where integument meets the nucellus |
Reserve food = nucellus; protection = integument; stalk = funicle.
Common traps
Radicle = Root, Plumule = shoot
Don't swap them. The radicle grows into the root (down); the plumule grows into the shoot (up). 'Radicle → Root' shares the R. Cotyledon and epicotyl are distractors — cotyledon stores food.
Apple flesh = thalamus, not petal/sepal/stamen
In the apple (a false fruit), the fleshy edible part develops from the thalamus (receptacle). Petal, sepal and stamen are distractors — they don't become the flesh.
Sunflower = inflorescence, not a single flower
Sunflower and marigold belong to the composite family; the showy 'flower' is an inflorescence of many small florets, not one flower.
Reserve food = nucellus (not integument or funicle)
The ovule part with the reserve food is the nucellus (the nutritive megasporangium). The integument protects, the funicle is the stalk, the chalaza is the base — none store the food.
Vegetative Propagation
Learn this subtopic in the notesVegetative propagation — the organs that do it
| Plant | Propagating part |
|---|---|
| Potato | Eye buds (on the tuber) Vegetative propagation through eye buds = potato (NDA 2024). |
| Ginger | Rhizome (underground stem) |
| Onion | Bulb |
| Sugarcane | Stem cuttings (nodes) |
Eye buds = potato; rhizome = ginger; bulb = onion; stem cuttings = sugarcane.
Common traps
Eye buds = potato
Propagation through 'eye buds' is potato (buds on the tuber). Ginger uses a rhizome, onion uses a bulb, sugarcane uses stem cuttings — don't confuse the propagating organ with the plant.