Plant Structure, Nutrition and Transport: Chapter 34

• Chapter 34 studies Plant Structure, Nutrition and Transport
• Students should gain an understanding with facts, methods, principles, generalizations, and theories
• Students should learn to apply knowledge and skills to benefit others

Types of Plants

• The differences between monocots and dicots should be identified

Structures of Plants

• A differentiation of main organ systems is needed
• Tissue systems in a plant body should be defined
• An explanation of the structure and function of the root and shoot systems is expected.
• The three main cell types in plants must be described
• An explanation of the vascular tissues in a plant body

Plant Nutrition

• A description of how plants obtain nutrients is needed
• An explanation of nitrogen fixation and how plants obtain nitrogen is needed.
• Importance and use of minerals for plants must be understood

Plant Transportation

• The movement of water and nutrients must be illustrated

Monocots

• Consist of grasses, lily family, palm trees, and banana plants
• Leaves have parallel veins
• Roots are fibrous and have numbers of roots equal in size
• Seeds have a single, small cotyledon that remains belowground

Dicots

• Represented the largest group of flowering plants
• Leaves are arranged in a netlike pattern
• Have taproots, which have a main root with many side branches
• Seeds have two cotyledons that emerge from underground

Root System

• Exists below ground
• Anchors the plant
• Absorbs water and nutrients from soil
• Transports water and nutrients
• May store food

Shoot System

• Exists aboveground
• Stems provide structure and support
• Transports food and water
• Leaves produce food through photosynthesis

Tissue Systems in the Plant Body

• Dermal tissue is its outermost layer
• Vascular tissues contain tubelike cells that conduct either water and food
• Xylem transports water
• Phloem transports food
• Ground tissue: any other type of tissue found in plants

Taproot

• Dicots
• Grows directly down into the ground
• Doesn't hold soil firmly, but grows more deeply

Fibrous Roots

• Monocots
• Form dense mats that help hold soil in place

Root Tip Tissue Systems

• Zone of cell division has a root apical meristem close to the root tip
• The root is protected by a conical patch of tissue (root cap)
• Root cap cells produce mucilage, and lubricate the extension of the root tip as it grows
• Zone of elongation exists before cells differentiate fully into specialized cells
• Zone of maturation contains root hairs that increase the surface area and water and nutrients are absorbed from the soil

Stems

• Allow growth against the pull of gravity
• Hold leaves up to absorb sunlight
• Transport water and food
• Dermal tissue exists at the external surface and ground tissue in the interior, with bundles of embedded vascular tissue

Stem Specialized tasks

• Protection (thorns)
• Climbing (grape vine tendrils)
• Belowground food storage (potatoes)

Leaves

• Stomata are regulated air pores, bordered by guard cells, in the dermal later of leaves, and are specialized for gas exchange
• CO2,O2, and water diffuse into and out of leaf when open
• Ground tissue houses vascular tissues containing pholem and xylem
• Photosynthesis takes places here
• Leaves are often covered in fuzzlike dermat hairs that can be deadly to insects and act as sunscreen

Main Leaf Functions

• The urn of the Malayan urn vine grows on other plants, not in soil, allowing aerial roots to grow inside "urns" formed by modified leaves
• Spines of a saguaro cactus are modified leaves that defend the plant from herbivores
• Tendrils of a pea plant are a modified leaf, and wrap around the stem, enabling the pea plant to grow upright

Dermal Tissues

• Protect from herbivores and pathogens
• Control gas exchange
• Limit water loss
• Have protective cells
• Epidermis
• Aboveground have a waxy cuticle
• Prevent water loss
• Protects from enemies

Dermal System

• Hairs protect the plant from UV rays or insects
• Stomata open when the guard cells bordering the stoma dilate with water
• Most plants open their stomata in the day and close them at night
• A plant under water stress will immediately close its stomata for conservation

Parenchyma cells

• Relatively large, living cells with thin walls
• Thin cell walls help them absorb water and nutrients
• In leaves and green stems, conduct photosynthesis
• Divide when necessary and help with wound repair
• Store surplus food
• Provide turgor pressure

Collenchyma cells

• Provide mechanical reinforcement in young, groing parts of the plant

Sclerenchyma cells

• Provide mechanical strength to non growing plant parts
• Reinforced with tough lignin
• Often dead at maturity

Fibers

• A type of very long sclerenchyma cells that occur in leaves, stems, or roots

Pholem

• Transports food, or sugars
• Sieve tubes are the food-conducting tubes in the phloem
• Sieve tubes are made of long, tubelike living cells, joined end to end and connected through sieve pores in their end walls, and lack a nucleus
• Companion cells connect to sieve tubes through which they supply sieve tube elements with macromolecules

Xylem

• Transports water and mineral nutrients
• Made of dead cells with thick, lignified cell walls to keep them from collapsing
• Tracheids are narrow conducting tubes
• Vessels are wider and can carry a larger volume of water
• The end walls of vessel elements have one or more large perforation openings

Plant Nutrients

• Plants need air, water, and of mineral nutrients
• Most of the weight of a living plant (living biomass) comes from water absorbed by the soil
• Much of the dry weight (biomass) comes from CO2 by the leaves and fixed into organic material through photosynthesis

Nutrition

• Mineral macronutrients (N,K,P) are needed in relatively large amounts (at least 1,000 mg of the nutrient per kg dry weight)
• Mineral micronutrients are needed in smaller amounts (less than 100 mg/kg plant dry weight)
• Minerals needed by plants are absorbed from soil
• Nitrogen (N), Phosphorus (P), and Potassium (K) are needed in the largest quantity by plants
• Synthetic fertilizer has little to no organic material
• Organic fertilizer, compost and manure contain many organic compounds
• Sponge-like texture of rotting water that mineral nutrients can dissolve
• Inorganic fertilizer particles act as "magnets" - mineral nutrients in the soil, keeping them from being washed out of reach of plant roots
• Inorganic fertiliser runs of to contaminant ground water

Cell Transportation

• Cell interior route crosses the plasma membrane of a root cell, and moves to the next via plasmodesmata
• Cell-wall bypasses cell interiors, nutrients dissolve in water and move along cell walls
• Endodermis functions as a screen for nutrients entering the vascular tissues
• Casparian strips block the cell-wall route

Plant Mineral Concentration

• Nutrient concentrations in the roots can be 10-10,000 times greater than those in soil
• Active transport is needed to transport minerals across membrane

Nitrogen

• Nitrogen-fixing bacteria help plants acquire this from the atmosphere
• Nitrogen gas is abundant in the atmosphere, but not available
• Plants absorb dissolved nitrate or ammonium
• Bacteria convert to ammonium

Carnivorous Plants

• Have evolved adaptations for acquiring minerals
• Mainly nitrogen and phosphorus in habitats deficient in these minerals
• Capture and digest animal prey in traps with many parts
• Minerals support plant growth and reproduction
• Green because do photosynthesis

Water Transport

• Plants lift water in their xylem-conducting elements with little metabolic energy
• Transpiration: the evaporation of water from the shoot system, drives the upward transport of water and dissolved nutrients

Food Transport

• Pressure differences between food-exporting and importing tissues drives the movement of food in the sieve tubes of pholem
• Food transport requires energy for these processes

Sugar Transport

• Active transport is needed for the uptake of sugars into sieve tubes
• Sugar in sieve tubes (10-30%) and in the leaf tissue
• Sugar into sieve tubes leads to osmotic uptake of water in the sleeve tubes
• Sugars are removed from the sleeve tubes
• C6H12O6 + O2 = CO2 + H2O + ATP

Transpiration

• Transpiration rates are highest when stomata are open during the day
• Rates are high when humidity is low, or windy
• Surface tension force that exists at all ar-water boundaries
• The collective pulling force on the xylem water column
• Evaporation of water from the shoot surface of the pant, mostly through open stomata

Xylem

• Transpiration is the evaporation of water molecules from plant surfaces
• Water uptake from soil cohesion is the transport of tension from leaf to root
• Root hair water molecules in soil

Explore plant structure focusing on monocots and dicots. Understand plant organ and tissue systems, root and shoot functions, and cell types. Learn about plant nutrition, nitrogen fixation, mineral use, and water and nutrient transport.