Plant Biology

• These are notes for Botany 20

Introduction to Plant Physiology

• Plant physiology includes dynamic processes in plant life such as growth, metabolism, and reproduction
• Crop physiology is an applied form of the field of plant physiology, used in genetically similar cultivated plants.

Importance of Plant Physiology

• Plant physiology helps in efficiently using nutrients
• Plant physiology aids with coping with biotic and abiotic stresses like drought, pollution, pests, and weeds
• Plant physiology increases crop yield, food, and feed quality

Kingdom Plantae Classifications

• Bryophytes are non-vascular plants
• Bryophytes exhibit haploid dominance and require water for fertilization
• Bryophytes are seedless and reproduce through spores
• Liverworts are a type of Bryophyte
• Ferns are vascular plants
• Ferns exhibit diploid dominance, needing water for fertilization and are seedless, using spores
• Gymnosperms are vascular plants exhibiting diploid dominance
• Gymnosperms use pollen for fertilization and produce naked seeds, such as Ginkgo
• Angiosperms are vascular plants that have diploid dominance
• Angiosperms use pollen for fertilization and have seeds inside an ovary such as monocots

Basic Requirements of Plant Life

• Light
• Carbon Dioxide
• Water
• Minerals

Unifying Principles of Plant Life

• Photoautotrophs
• Cellulosic cell wall
• Sedentary
• Avoids desiccation
• Transport processes
• Oxygen production

The Plant Body

• Plant body parts include the shoot tip (apical bud), epidermis, lateral bud, flower, node, internode, vascular tissues, ground tissue, leaf, primary root, shoot, root, lateral root, root hairs, and root tip with a root cap

Plant Cell Types

• Parenchyma
• Collenchyma
• Sclerenchyma
• Parenchyma cells are generic, abundant, and versatile, functioning in storage and metabolism
• Parenchyma cells can differentiate and are alive at maturity and have a primary cell wall
• Collenchyma cells are a flexible support, like glue, found in growing plant organs
• Collenchyma cells originate from parenchyma cells, stay alive at maturity, and may have primary and secondary cell walls, like strings in celery
• Sclerenchyma cells are rigid and function in supporting and strengthening non-extending regions of plants
• Sclerenchyma cells have thick, non-stretchable secondary cell walls and are dead when mature
• Sclerenchyma cells come in two types, fibers which are long, slender strands, and sclerids, which are short with varying shapes and groups

Plant Tissue Systems

• Ground tissue handles photosynthesis, storage, and structural support
• Vascular tissue distributes absorbed water, mineral ions, and products of photosynthesis
• Dermal tissue covers and protects exposed plant surfaces

Simple Tissues: Ground Tissues

• Parenchyma makes up most of the primary growth, which involves secretion, storage, photosynthesis, and repair
• Collenchyma supports growing plant parts through pectin for flexibility
• Sclerenchyma contains lignin for support; its cells are dead at maturity

Complex Tissues: Vascular Tissues

• Xylem transports water and ions and consists of tracheids and vessel members and is filled with lignin
• Phloem transports sugar and organic solutes with sieve tubes and companion cells

Complex Tissues: Dermal Tissues

• Epidermis is a single outer layer with a waxy protective cuticle with specialized cells for stomates
• Periderm replaces the epidermis in woody plants

Other Plant Tissues

• Apical Meristems are at the shoot and root tips, increasing plant length
• Intercalary Meristems add length to the plant
• Lateral Meristems add girth by producing wood and bark

3 primary meristems

• Ground meristem forms ground tissues
• Protoderm forms skin coverings
• Procambium forms plant plumbing

Vegetative Organs: Roots

• Roots are responsible for anchoring plants and absorbing water and minerals, as well as storage

Longitudinal section of roots includes

• Root cap
• Zone of cell division
• Zone of cell elongation
• Zone of maturation

Cross section of root

• This section of root contains xylem and pholem.
• Cortex
• Epidermis
• Root hairs
• Absorb water and minerals

Root Structure

• Key parts include: Epidermis, ground tissue, vascular tissue, ground meristem, procambium, protoderm, quiescent center, apical meristem, lateral root cap, columella root cap

Stems

• Stems support leaves and act as conduits for transport and storage

Woody Dicots

• Woody dicots have discrete vascular bundles replaced by continuous rings of xylem
• Each ring of xylem is produced during one growing season, and vascular cambium is present

Stems: Secondary Growth

• Vascular tissue (xylem) makes up the bulk of the stem and forms tree rings

Leaves

• Leaves are the main location of photosynthesis

Monocotyledon

• Plants contain one cotyledon
• Parallel veins
• Vascular bundles are usually complexly arranged
• Fibrous root system
• Flowers in multiples of three

Dicotyledon

• plants contain two cotyledons
• Netlike veins
• Vascular bundles in rings

Leaf Parts

• Blade
• Petiole
• Pair of stipules

Other Plant Tissues

• Taproot is present in a plant
• Flowers in multiples of four or five

Plant Cell Wall

• Contains Pectin, Hemicellulose and Cellulose
• Plants have unique cell wall layers, comprising of a Middle lamella, Primary wall and Secondary wall

Cell Wall of Mature Cell

• Contains 3 layers of secondary wall

Plasma Membrane

• Controls selective permeability of membranes to allow water, ethanol, amino acids, glucose etc to move in and out of the cell

Different Parts of the Plant Cell

• The Nucleus is the control centre and stores genetic information
• Nuclear pores allow passage between nucleus and cytoplasm

Endomembrane System

• Transports vesicle from ER
• Plamas Membrane
• Vacuole
• Lysosome
• Golgi apparatus

Endosymbiotic Hypothesis for the Origin of Mitochondria and Chloroplast

• Contains DNA for time for the protoplasm and endoplasmic reticulum

Mitochondria

• Powerhouse for the cell
• ATP production
• Cellular respiration
• Has its own genome

Plastids

• Chloroplasts create Chlorophyll in leaves and stems for photosynthesis
• Thylakoids area of photosynthesis, and contain a Stroma - calvin cycle
• Amyloplasts - for starch storage, colourless. Roots, seeds, and fruits
• Chromoplasts cause red and yellow pigments and coloured petals and fruits.

Vacuole

• Stores water, ion, and nutrients
• Receptacle for waste products
• Turgor pressure regulation by osmosis

Vesicles and Microbodies

• Vesicles store or transport substances
• Peroxisomes – has enzymes that break down hydrogen peroxide, and other toxins
• Glyoxysomes – break down fats

Cytoskeletons

• Network of protein fibers.

Functions include

• Internal support and structure
• Transport of organelles
• Cell mobility

Introduction: Energy and Thermodynamics

• Energy is the capacity to do work
• Potential energy is stored, at rest like chemical energy
• Kinetic energy accomplishes work in motion, like heat or light

Laws of Thermodynamics

• Energy of the universe is constant, but that entropy continues to increase toward a maximum

1st Law of Thermodynamics

• Total energy in the universe is constant
• Energy can be changed from one form to another but cannot be created or destroyed

2nd Law of Thermodynamics

• The natural tendency of the universe is towards increasing disorder
• If potential energy of a final state is lower than an initial state, it's exergonic
• If potential energy of a final state is higher than an initial state, it's endergonic
• Spontaneous events occur without external input

Free Energy (Gibbs Free Energy)

• Spontaneity depends on both enthalpy and entropy.

Metabolic categorization

• Catabolic processes are degradative and exergonic
• Anabolic processes are synthetic and endergonic

An Overview of Metabolism

• Catabolic pathways involve breaking down complex substrates into simple end products to create chemical energy and raw materials
• Anabolic pathways synthesize complex end products from simple substrates, requiring energy via ATP and NADPH.

Enzymes

• Enzymes are a Biological catalysts and agents of life

Propoerties of Enzymes

• Specificity acts on a single substrate and is highly specific
• Catalytic efficiency increases times over uncatalyzed reaction, and mostly reversible except for decarboxylases and hydrolases.

Enzyme Structure

• Includes primary and secondary amino acids
• Tertiary 3D shape of polypeptide subunit
• Quaternary association of two or more subunits.

Enzyme Composition relates to properties

• Prosthetic group - tightly bound organic molecule, more or less permanently associated with the enzyme protein (i.e sugar)
• Cofactor not tightly bound, transiently associated with the protein

Mechanism of Enzyme Action

• Enzymes lower the barrier of activation energy.

Model of Enzyme-Substrate Interaction

• Involves key changes around the active site

Kinetics of Enzyme-Catalysed Reaction

• The rate remains relatively constant (steady state) until the substrate is depleted
• Reaction rates depend on the number of successful collisions between substrate and enzyme molecules which in turn depend on concentration

Environmental Factors Affecting Enzyme Activity

• Changing pH influences the ionization of the substrate resulting in the loss of Hydrogen bonding
• Denaturation state occurs because of presence of charged or uncharged amino or carboxyl group

Enzyme Activity

• Involves Gene expression as cells can control the flux of metabolites through regulates enzyme activity through genes, hormones etc

Plant Respiration

• Higher plants are aerobic organisms needing oxygen for normal metabolism
• Plants obtain energy and carbon by oxidizing photoassimilates

Aerobic Respiration Stages

• Glycolysis
• Krebs Cycle
• Electron Transport System

Plant Respiration Overview

• Direct oxidation of hexose by molecular oxygen while releasing free energy as heat
• Provides the carbon skeleton for a number of plant products and are utilized for plant growth and maintenance

Glycolysis

• Converts sugars to pyruvate and takes place in the cytosol.
• ATP is synthesized through substrate level phosphorylation
• Partial oxidation of hexose (2 molecules of pyruvic acid/hexose) → uses no O2 and releases no CO2

Glycolysis Products

• Produces ATP
• Yields molecules that can be removed from the pathway for synthesis of other compounds

Fate of Pyruvate

• When O2 is limiting, fermentation accumulates and is used, and depends if its Ethanol or Lactic Acid.

Krebs Cycle

• Krebs Cycle is stepwise where substrate is oxidized and its energy conserved
• Three molecules of ATP are formed from each pair of electrons donated by NADH

Electron Transport System

• The electrons gradually lose energy as they pass along the chain of electron carriers.
• The released energy pumps H+ into the intermembrane space, creating an H+ or pH gradient across the membrane
• Electrons associated with either NADH or FADH2 are transferred through specific electron carriers that make up the Electrocute transport system. (ETS)

Oxidative Metabolism in the Mitochondrion

• Step 1: High energy electrons are passed from FADH2 or NADH
• Step 2: The controlled movement of protons back across the membrane.
• ATP is formed by the controlled movement of H+ back across the membrane through the ATP-synthesizing membrane

Pentose Phosphate Pathway

• is hexose monophosphate shunt; Oxidative pentose phosphate and is related to glucose degradation

Other features of plant Respiration

• Involves Substrate Availability, and Oxygen Availability.
• It is also dependent on Temperature and influenced by plant Type and Age

Functions of Respiration

• Provides ATP to for cellular work and biosynthesis

Lipids

• Plants produce Membrane lipids and occur in ER and mitochondrial membrane and are triglycerides

Transketolase

• is a type of carbohydrate catalyst

Functions of Respiration

• Wounding - facilitates the entry of O

Secondary Metabolites

• Contains Primary and Secondary diversions

Primary Metabolites

• Contains products from plants vital processes and have Chlorophyl and Proteins.

Secondary Metabolites

• Contains products from a major pathway and has metabolic distributions amongst different parts.

Principal Groups of Secondary Metabolites

• Terpenoids
• Used to draw from acetly CoA
• Essential oils
• Phenolics- Draws from entohere 4- phosphate

Explore plant cell types, tissues, and structures. Understand the roles of meristems, vascular cambium, and ground tissue. Learn about plant classification based on leaf veins and root systems.