Plant Growth and Development

• Study notes are presented below

LU4.1: Growth and Development

• Growth is the permanent increase in a plant's size, considering cell size, tissue expansion, and overall mass
• Development is the sequence of changes in a plant's life, from germination to aging
• Morphogenesis is a part of development and refers to the form and structure acquisition
• Differentiation is the transformation of generalized cells into specialized ones

Stages of Plant Growth

• Seed Germination: The seed absorbs water and starts metabolic activity
• Seedling Development: The seedling grows roots and shoots and establishes itself in the soil
• Adult Plant Formation: The stage where the plant reaches maturity with developed tissues, organs, and structures

Meristems (Growing Regions)

• Apical Meristem: Located at the tips of roots and shoots and responsible for primary growth to increase plant length
• Lateral Meristem: Found near the sides of stems and roots and responsible for secondary growth which increases the plant's width

Phases of Cell Growth

• Phase of Division (Meristematic Phase): Mitotic cell division occurs in the meristematic zone, and produces new cells for growth
• Phase of Elongation: Cells can increase up to 10x their original length, causing root penetration further into the soil, and adds overall size to the plant tissues
• Phase of Differentiation (Maturation): Differentiation is cells undergoing specialization based on their position in the organ

Primary vs Secondary Growth

• Primary Growth: Happens first and grows the plant length above and below ground, driven by apical meristems
• Secondary Growth: Happens after primary growth increasing diameter and strength controlled by lateral meristems and includes growth from axillary buds

LU4.2: Factors That Affect Plant Growth

• Light: Essential for photosynthesis, regulating stomata and assists floral induction
• Light Quality affects plant processes like growth, leaf production and flowering
• Water: Makes up 90% of the plant body. Necessary for cell expansion, photosynthesis & nutrient transport
• Temperature: A key factor for metabolic processes like transpiration, photosynthesis, and flowering
• Optimal temperature accelerates growth
• Nutrients: Plants need macronutrients (like nitrogen, phosphorus, calcium) & micronutrients (like iron,boron, and manganese)
• Nutrient Deficiency: Even one will stunt growth

Growth Curve

• Lag Phase: Initial growth is slow, with growth under 25%
• Development indicators are seed germination, seedling emergence, and plant establishment
• Log Phase: Rapid growth phase with growth under 70%
• Development indicators are leaf production, branching and tillering
• Diminishing Phase: Growth slows down, with growth at 85%
• Development indicators are flowering and seed production
• Stationary Phase: Growth stops, with almost full growth
• Development indicators are ripening, maturity and senescence

LU5.1: Plant Tissue Systems

• Dermal Tissue System Description: It forms the "skin" of the plant, primarily for protection
• Formed of a single layer of cells, predominantly parenchyma cells
• Epidermis: A single layer of tightly packed cells covering plant surfaces, which protects against water loss and pathogens
• Periderm: Found in stems of plants when the plant has secondary growth and used to replace the epidermis

Ground Tissue

• Constitutes the majority of the plant body and includes photosynthesis, storage and structural support
• Cell Types: Parenchyma with living cells that perform metabolic activities
• Collenchyma are living cells with unevenly thickened walls for flexible support
• Sclerenchyma is non-living cells with thick strong walls to support mature sections of the plant
• Fibers: Long, slender cells occurring in bundles (e.g., hemp, flax)
• Sclereids: Short, irregularly shaped cells that exist in seed coats & nut shells.

Vascular Tissue

• Description: Specialized for the transport of water, nutrients, and food and provides structural support
• Xylem Functions: Conducts water and dissolved minerals
• Cells: Tracheids and vessel elements and parenchyma and sclerenchyma
• Phloem Functions: Transports food (mainly sucrose)
• Cell Types: Sieve tubes, companion cells, pholem fibers, and parenchyma

LU5.2: Cells

• Structure: Protoplasm is the living content of the cell, containing of two main parts: Nucleus and Cytoplasm
• Nucleus: The control core of all instructions
• Cytoplasm: A gel-like matrix where the components are stored

Cell Development

• A growing plant cell releases a thin primary cell wall that expands as the cell grows
• When growth stops, more layers known as the secondary cell wall grow, which are formed of a different composition and enhance strength

Permanent Tissue Types

• Ground Tissue: Made of Parenchyma, Collenchyma, Sclerenchyma
• Vascular Tissue: Xylem and phloem

Secretory Tissue

• Specialized cells that produce and secrete items like resins, oils & slime
• Internal: Resin/oil vessels, Laticifers
• External: Hydathodes, digestive glands and Nectaries
• Resin & Oil Vessels: There are ducts enclosed by epithelial cells that produce oils and resins
• Laticifers: It contains cells or a string of cells carrying latex
• Hydathodes: Glands releasing water during liquid discharge.
• Digestive Glands: Located in insect-eating plants.
• Nectaries: The nectar is released as a mechanism to attract pollinators and exists in flowers or plant parts

LU6.1: Rhizosphere

• It is a region around a plant's root that sees interactions between roots & microorganisms

• The rhizosphere consists of three zones:

• The Endorhizosphere: Which includes the cortex and endodermis, has microbes and ions

• The Rhizoplane: Zone next to the root

• Ectorhizosphere: The outer zone that goes to bulk soil

Root Exudates & Mucilages

• Roots are made of mucilages and soluble elements.
• Mucilages: Viscoelastic gels including polysaccharides,
• Functions: Attract helpful microbes and can act as bait for hazardous microorganisms

Rhizodeposits

• They are materials transferred through roots to land
• Includes a loss of head & border cells, a loss of root loss and the loss of carbon to symbionts

Rhizosphere

• Root carbon is delivered in the form of organic or inorganic (like bicarbonate) formers that effect procedures
• The type & sum of elements depend on plant type and climate/nutrient conditions

LU6.2: Root Hairs

• Find a couple of centimeters from the tip
• Act to retain water and other materials
• Contribute to bacterial stimulation

Microbe-Plant

• Higher in the rhizosphere compared to bulk soil/ microbial competition
• Key microbial relationships may require symbiosis
• Rhizobia: Plants convert air nitrogen to feed plant
• Fungi: two types/form dense in cells known as hyphae.
• Bacteria: Assist root system to grow.

LU7.1: Challenges

• Dominance of wheat/corn provides 50% of food while these crops are a small fraction of global biodiversity
• Current transportation relies on long distance markets which affects feeding systems.
• Current crops need volatile climate conditions

LU7.2: Solutions

• Expanding diversification through communities on new research
• Enhancing current crops and environmental prices
• Improving agricultural diversity
• Development of new crops for bio fuel production/ strong capabilities
• Enhancing carbon fixing to boost natural ecosystem

Study notes on plant biology. The notes cover growth, permanent increase in size, and development, the sequence of changes in a plant's life, from germination to aging. It also describes different stages, meristems and growing regions of plants.