Plant Tissues and Adaptations

• Plant cells have cell walls and a large central vacuole
• Plants have many types of cells adapted for particular roles
• Cells are composed of tissues, tissues are composed of organs, organs are composed of organ systems

Plant Cell Types

• The three plant cell types are parenchyma, collenchyma, and sclerenchyma
• Three cell types form particular plant tissues

Parenchyma

• Functions include storage, photosynthesis, gas exchange, protection, tissue repair, and replacement
• These cells are flexible, have thin walls, and are found throughout the plant
• They are important for plant structure and can perform a wide array of functions
• They can divide when mature to repair the plant
• These cells in leaves and green stems have chloroplasts to perform photosynthesis and produce glucose
• Parenchyma in roots and fruits have large central vacuoles to store starch, water, and oils

Collenchyma

• Provides support for surrounding tissues
• Provides flexibility for the plant
• Responsible for tissue repair and replacement
• These cells can have unevenly thickened cell walls
• Plants are able to bend without breaking because of this growth pattern, these cells are flexible and can stretch
• Able to undergo cell division at maturity

Sclerenchyma

• Provides support
• Responsible for material transport
• Lacks cytoplasm and other living elements when mature, but the thick, rigid cell walls remain
• There are two types of sclerenchyma cells: sclereids and fibers
• Sclereids, or stone cells, give pears their gritty texture are shorter than fibers and are irregularly shaped, also function in transport
• Fibers are needle-shaped with thick cell walls and small interior spaces, form a strong, elastic tissue when stacked end-to-end

Plant Tissues

• A plant tissue is a group of cells working together to perform a function
• Plant tissues can have one or many types of cells
• There are four types of plant tissues: meristematic, dermal, vascular, and ground

Meristematic Tissue

• Responsible for most plant growth
• Stems and roots increase in length due to apical meristems
• A plants vascular cambium is a meristematic tissue, produces cells that increase root and stem diameters
• Apical meristems cause primary growth, or lengthening
• Occurs at the tips of shoots and roots and produces new leaves and flowers
• Lateral meristems cause secondary growth, widening
• Occurs at the cambium and produces bark on trees
• Apical meristems are located at the tips of stems and roots, increases length at tips
• Intercalary meristems are located between the tip and base of stems and leaves, increases length between nodes
• Lateral meristems are located at the sides of stems and roots, increases diameter

Dermal Tissue - The Epidermis

• The outer covering of a plant
• Epidermal cells resemble jigsaw puzzle pieces
• The outermost layer of cells features adaptations that prevent water loss and protects the plant
• A cuticle, a waxy coating, coats exposed parts, keeps plants from drying out, and prevents bacteria and microorganisms from entering
• Guard cells control the opening and closing of stomata
• Some epidermal cells include trichomes to prevent insect and animal predation
• Root hairs are extensions of root epidermal cells

Vascular Tissues

• Xylem, vascular tissue, carries water
• Phloem, vascular tissue, carries food in vascular plants

Ground Tissue

• Plant tissues that are not meristematic, dermal, or vascular
• Consists of parenchyma, collenchyma, and sclerenchyma cells
• Functions include photosynthesis, storage, and support

Roots

• Has five main functions
• Anchors the plant
• Takes in water and minerals
• Brings water and minerals up to the stems using xylem
• Brings dissolved food from the stems to the roots using phloem
• Stores food
• Two main types are taproot and fibrous root systems
• Taproot systems anchor the plant and store food, for example, beets and carrots
• Fibrous root systems also anchor the plant and are good for rapid water storage
• Other root types are adapted to diverse environments
• Pneumatophores supply oxygen to roots submerged in water
• Adventitious roots form unusual support structures

Stems

• Stems support leaves, fruit, flowers, and branches
• Stems transport water, nutrients, and solutes between roots and leaves
• Some stems are photosynthetic, which helps in food storage
• Stems can store materials necessary for life, such as water, starch, and sugar
• Types of stems includes the following:
• Tuber: food storage
• Rhizome: food storage and asexual reproduction
• Runner: asexual reproduction
• Bulb: food storage
• Corm: food storage
• Apical meristem cells increasing the length of the stem
• An increase in stem diameter in annual plants is mostly due to cell size increase
• In perennial eudicots and conifers, increasing stem diameter is due to vascular cambium cells
• Xylem and pholem production throughout the year can produce annual growth rings, tree age can be estimated by the number of annual growth rings at the base of its trunk

Leaves

• Responsible for creating food
• Captures sunlight to make food through photosynthesis
• Differences in the size, shape, color, and texture of leaves helps identify types of plants
• Simple leaves have leaf blades that are not divided into smaller parts
• Compound leaves have leaf blades that are divided into two or more parts called leaflets

Plant Responses

• A nastic response causes movement that is not dependent of the direction of a stimulus
• Nastic responses are not for growth, they are reversible, and can be repeated
• A tropism is a plant growth response due to an external stimulus
• If growth is toward the stimulus, it is a positive tropism
• If growth is away from the stimulus, it is a negative tropism

Types of Tropism

• Phototropism involves light, which makes a plant grow toward the light source
• Gravitropism involves gravity, which causes positive downward and negative upward growth
• Thigmatropism involves mechanical, which causes growth toward a point of contact

Explore plant cells, tissues like epidermis and phloem, and root adaptations. Understand how these structures contribute to water transport, defense, nutrient storage and survival in diverse environments. Learn about root hairs, pneumatophores, and fibrous root systems.