Soil Formation, Soil Properties, Plant Nutrition, Tissues and Root Systems – Video Notes Flashcards

Flashcards cover soil formation, soil properties, soil horizons, nutrient requirements (macro- and micro-nutrients), soil pH, plant tissues, root biology, root systems, specialized roots, root symbioses, and starchy root crops as described in the video notes.

What is soil?

A dynamic, complex, constantly changing part of Earth’s crust that is essential for life (plants, animals, humans).

What are the main components of soil?

Minerals (sand, silt, clay, rocks); Organic matter (humus, dead plants, roots, animals); Microorganisms (bacteria, fungi); Air & water.

Name the five factors of soil formation.

Parent material, climate, vegetation & living organisms, topography, time.

What are the horizons in a soil profile and their key features?

O horizon: organic matter; A horizon (Topsoil): 10–20 cm, dark, OM rich; E horizon: leached layer (may/may not exist); B horizon (Subsoil): 30–90 cm, more clay, lighter color; C horizon: weathered parent material; R horizon: bedrock.

What is parent material and its major types?

Igneous (volcanic) rocks; Sedimentary rocks (deposited by water/wind/glaciers); Metamorphic rocks (altered by heat & pressure).

How does climate affect soil formation?

Deserts: poor soils; moderate rainfall: best soils; high rainfall: leaching of minerals; freeze–thaw action cracks rocks aiding soil formation.

How do living organisms influence soil formation?

Decompose organic matter to humus; roots produce CO2 that forms acids to dissolve minerals; ants, worms, and burrowing animals mix soil; good topsoil ~25% air, 25% water, 48% minerals, 2% OM.

How does topography affect soil development?

Steep slopes cause erosion; flat poorly drained areas pond; best on gentle slopes with drainage.

What are sand, silt, and clay particle size ranges?

Sand: 0.05–2 mm; Silt: 0.002–0.05 mm; Clay: <0.002 mm.

What is loam and why is it important for farming?

Loam = 40% sand, 40% silt, 20% clay; considered ideal for farming due to balanced properties.

What is soil structure and why is pore space important?

Particles form aggregates; 40–60% pore space; large pores enable air & drainage; small pores retain water.

Define the three states of water in soil and terms FC, PWP, and PAW.

Hygroscopic: bound and unavailable; Gravitational: drains quickly; Capillary: held against gravity and available to plants; FC = water left after draining; PWP = soil too dry for plants; PAW = water between FC and PWP.

What does soil pH measure and why does it matter?

Acidity/alkalinity of soil; extreme pH can be toxic to roots and microbes; influences nutrient availability.

How can soil pH be corrected for acidic and alkaline soils?

Acid soils: add lime (Ca/Mg compounds); Alkaline soils: add sulfur.

Name the six macronutrients used by plants.

Nitrogen (N), Phosphorus (P), Potassium (K), Calcium (Ca), Magnesium (Mg), Sulfur (S).

What are the common deficiency symptoms for nitrogen (N)?

Yellowing of older leaves first (uniform yellowing).

What are the common deficiency symptoms for phosphorus (P)?

Stunted growth; dark green to purplish leaves.

What are the common deficiency symptoms for potassium (K)?

Yellowing at leaf margins, progressing inward; brown tips.

What are the common deficiency symptoms for calcium (Ca)?

Abnormal tips/margins; roots may die.

What are the common deficiency symptoms for magnesium (Mg)?

Yellowing between leaf veins, dead spots, leaf curl.

What are the common deficiency symptoms for sulfur (S)?

Pale green, yellow veins, dead spots.

Name the three key micronutrients listed.

Iron (Fe), Manganese (Mn), Boron (B) (also Zn, Cu, Mo; sometimes Na, Cl, Co).

What is the deficiency symptom for iron (Fe)?

Pale green base of young leaves.

What is the deficiency symptom for manganese (Mn)?

Small dead spots; yellowing with veins remaining green.

What is the deficiency symptom for boron (B)?

Brittle stems/petioles; young leaves break off.

What is the general function of macronutrients in plants?

Support essential processes like growth, metabolism, and structure (e.g., N for proteins, P for ATP, K for enzyme activity, Ca for cell walls, Mg for chlorophyll, S for amino acids).

What are the key facts about plant nutrients mentioned?

Macronutrients: N, P, K, Ca, Mg, S; Micronutrients: Fe, Zn, Cu, Mn, Mo, B (plus sometimes Na, Cl, Co); N, P, K, Ca make up ~99% of plant nutrient content.

What is a tissue in plants?

A tissue is a group of cells with a common structure and function.

What is an organ in plants?

Several tissue types working together (e.g., root, stem, leaf).

What is anatomy vs physiology in plants?

Anatomy = structure (cells and tissues); Physiology = function (how tissues and organs work.)

What is dermal tissue and its key features?

Outermost layer (epidermis); often one cell thick; covered with a cuticle (cutin) to reduce water loss.

What are trichomes and stomata in dermal tissue?

Trichomes are hairs for protection and reducing water loss; stomata (guard cells with chloroplasts) regulate gas exchange.

What is ground tissue and its main roles?

Forms cortex, pith, and mesophyll; functions include storage, photosynthesis, and support.

Name the ground tissue types and one function each.

Parenchyma: storage, healing, photosynthesis; Collenchyma: flexible support; Sclerenchyma: rigid support with lignified walls (includes sclereids and fibers). In aquatic plants, parenchyma may form aerenchyma.

What is xylem and its primary function?

Transports water and minerals from roots to shoots; dead at maturity; includes vessels and tracheids.

What are vessels and tracheids?

Vessels are tube-like conduits with perforation plates; Tracheids are tapered cells with pits for water movement.

What is phloem and its function?

Transports sugars (food) from photosynthesis; living at maturity; contains sieve tube elements and companion cells.

What are sieve tube elements and companion cells?

Sieve tube elements form long tubes with sieve plates and lack a nucleus; companion cells assist sieve tubes.

What are the main functions of roots?

Anchorage, Absorption (water and minerals), Conduction (to stem), Storage (food and water), sometimes reproduction and symbiosis.

Differentiate the three root systems with examples.

Taproot system: primary root grows deep (dicots, e.g., carrot, dandelion); Fibrous root system: many thin roots (monocots, e.g., grasses, maize); Adventitious roots: arise from stems/leaves (e.g., maize prop roots, ivy climbing roots, banyan aerial roots).

What is the root cap and apical meristem?

Root cap protects the tip and secretes mucilage to aid movement; apical meristem is the region of cell division.

What are the regions of a growing root?

Region of elongation (cells lengthen) and Region of maturation (root hairs form for absorption).

What is the endodermis and Casparian strip?

Endodermis is the innermost cortex layer; Casparian strip regulates movement of substances into the xylem.

What is the pericycle and stele in roots?

Pericycle is just inside the endodermis and gives rise to lateral roots; the stele is the vascular cylinder containing xylem and phloem.

What are storage, water-storage, and propagative roots?

Storage roots store starch (e.g., carrot, sweet potato); water-storage roots store water (desert species like manroot); propagative roots produce adventitious buds that become new stems (suckers in fruit trees).

What are pneumatophores and haustoria?

Pneumatophores are breathing roots in mangroves; haustoria are parasitic roots that penetrate host plants to steal water/nutrients.

What are the quick test facts about roots?

Root hairs = absorption; Dicots typically have a taproot; Monocots typically have fibrous roots; Casparian strip is in the endodermis; Pericycle forms lateral roots; Pneumatophores occur in mangroves; Adventitious roots form from stems or leaves.

What are some examples of specialized roots involved in starch storage?

Food-storage roots like sweet potatoes store large quantities of starch; carrots, beets, and radishes store food in a combination of root and stem tissues.

Name examples of modified roots and their uses in agriculture or biology.

Aerial roots (ivy, fig trees, some orchids), contractile roots (pull plants deeper into soil), buttress roots (stability in tropical trees), prop roots (maize) for support.

What roles do mutualistic associations play with roots?

Mycorrhizae: fungi help absorb water and minerals, plant provides sugars; Root nodules: Rhizobium bacteria fix atmospheric nitrogen in legumes.

Which crops are highlighted as starchy staples and what is notable about them?

Sweet potatoes (Ipomoea batatas) and cassava (Manihot esculenta); sweet potatoes store starch and are propagated by vine cuttings; cassava is a tuberous root rich in starch but low in protein; some bitter varieties detoxified before consumption.

Name all the specialised roots?

Food storage (e.g. sweet potatoes); water-storage (in arid regions; e.g. manroot); propagative (e.g. cherries - produce adventitious buds that develop into suckers); pneumatophores (swamp plants - spongy roots that grow above water to enhance gas exchange); aerial roots (e.g. fig trees); contractile roots (contract to pull plant deeper into soil)