Botany Complete Cheat Sheet: Plant Anatomy, Photosynthesis & Phytohormones - NEET 2027

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1. Plant Anatomy & Tissues

Plant tissues are broadly classified into meristematic and permanent tissues based on their capacity to divide. Understanding structural organization is vital for solving diagrammatic and statement-based NEET questions.

Meristematic Tissues

Meristematic tissues consist of actively dividing, undifferentiated cells responsible for plant growth.

• Apical Meristems: Positioned at the tips of roots and shoots. Responsible for primary growth, increasing overall plant length.
• Lateral Meristems: Positioned parallel to the long axis of organs (e.g., vascular cambium and cork cambium). Responsible for secondary growth, increasing girth or diameter.
• Intercalary Meristems: Located at nodes or bases of leaves (common in monocots like grasses), allowing rapid elongation after damage.

Permanent Tissues

Permanent tissues consist of mature, specialized cells that have lost the power of division.

• Simple Permanent Tissues: Composed of a single cell type.
  • Parenchyma: Thin-walled living cells responsible for storage, secretion, and photosynthesis.
  • Collenchyma: Living cells with unevenly thickened walls (pecto-cellulose); provides flexible mechanical support to young growing organs.
  • Sclerenchyma: Rigid, dead cells at maturity with thick lignified walls; provides structural support (fibers and sclereids).
• Complex Permanent Tissues: Composed of multiple cell types working together.
  • Xylem: Conducts water and inorganic nutrients. Components include tracheids, vessels, xylem fibers, and xylem parenchyma (the only living component).
  • Phloem: Transport organic solutes (photosynthates). Components include sieve tubes, companion cells, phloem fibers (dead at maturity), and phloem parenchyma.

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2. Photosynthesis & Cellular Respiration

Light Reactions (Thylakoid Membrane)

Light-dependent reactions convert solar energy into chemical energy (ATP and NADPH) through photophosphorylation. Photolysis of water occurs via Photosystem II (PSII), releasing oxygen as a byproduct.

\[\text{H}_2\text{O} + \text{NADP}^+ + \text{ADP} + \text{P}_i \to \text{O}_2 + \text{NADPH} + \text{ATP}\]

Electrons flow through a membrane-bound electron transport chain (ETC) from PSII to PSI, establishing a proton gradient across the thylakoid membrane that drives ATP synthesis.

Calvin Cycle / Dark Reactions (Stroma)

Light-independent reactions take place in the stroma where chemical energy is utilized to fix carbon dioxide into carbohydrates.

\[\text{CO}_2 + \text{NADPH} + \text{ATP} \to \text{G3P} + \text{NADP}^+ + \text{ADP}\]

The Calvin cycle comprises three primary stages:

1. Carbon Fixation: Catalyzed by the enzyme RuBisCO (Ribulose-1,5-bisphosphate carboxylase-oxygenase).
2. Reduction: Conversion of fixed carbon into triose phosphates (G3P) using ATP and NADPH.
3. Regeneration: Restoration of the CO2 acceptor molecule RuBP (Ribulose 1,5-bisphosphate) requiring ATP.

Cellular Respiration Phases

1. Glycolysis: Takes place in the cytoplasm under both aerobic and anaerobic conditions. Converts one molecule of Glucose into two molecules of Pyruvate, yielding a net gain of \(2\text{ ATP}\) and \(2\text{ NADH}\).
2. Krebs Cycle (TCA Cycle): Occurs within the mitochondrial matrix. Acetyl-CoA is broken down completely, generating \(\text{CO}_2\), \(\text{NADH}\), \(\text{FADH}_2\), and \(\text{GTP}\).
3. Oxidative Phosphorylation: Occurs across the inner mitochondrial membrane. Chemiosmosis mediated by ATP synthase utilizes electron transfer energy to yield approximately \(32\text{--}34\text{ ATP}\) per glucose molecule.

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3. Plant Hormones (Phytohormones)

Plant growth regulators control various physiological functions, from seed germination to organ senescence.

Hormone	Primary Physiological Functions
Auxin (IAA)	Promotes cell elongation, maintains apical dominance, initiates adventitious root growth, and prevents premature leaf fall.
Gibberellins (GA)	Stimulates internodal stem elongation, breaks seed dormancy, induces bolting in rosette plants, and promotes seed germination.
Cytokinins	Promotes active cell division, delays leaf senescence (Richmond-Lang effect), and promotes lateral bud growth by counteracting apical dominance.
Ethylene	Gaseous hormone regulating fruit ripening, organ abscission, triple response in seedlings, and root hair formation.
Abscisic Acid (ABA)	Acts as a stress hormone, induces stomatal closure during water deficit, and promotes seed dormancy and stress tolerance.

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4. NEET PYQ Analysis & NTA Pattern Insights

Chapter Weightage & Frequency Analysis:

• Plant Anatomy: Accounts for approximately 2 to 4 questions per year in NEET. Questions frequently focus on comparing monocot vs. dicot root/stem structures, complex tissue functions, and types of meristems.
• Photosynthesis & Respiration: Highly high-yield chapters generating 4 to 6 questions. High emphasis on the location of cellular processes, key enzymes (RuBisCO, PEPcase), stoichiometry of ATP synthesis, and Z-scheme steps.
• Plant Hormones: Generates 2 to 3 straightforward matching or assertion-reason questions targeting specific hormonal functions (e.g., bolting, stomatal closure, apical dominance).

NTA Exam Pattern Strategy: Master NCERT line-by-line descriptions, chemical structures of phytohormones, and schematic flowcharts for metabolic pathways like the Calvin Cycle and Glycolysis.

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5. People Also Ask (FAQ)

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