By: Emily, Lauren, and Rebecca

Plant Structure, Growth, and Development

Plants• Plasticity: where a plant is able to mold itself due its environment• Morphology: is the plants external form• Tissues: a group of cell with common function and structure• Organs: many tissues that work together to preform work• Protoplast: area of cell not including the cell wall (able to determine

function)

Plant Organs: Roots, Stems, and Leaves• Root System: portion of plant responsible for

absorbing water and nutrients•  Root: the organ that anchors the plant, absorbs

water and nutrients Taproot v. Lateral roots:• Taproot: the main vertical root which

developed from the embryonic root (Taproot system)

• Lateral roots: or Branch roots which are the roots coming off of the taproot and acts as a storage area

• Fibrous Root System: usually has no main root but a bunch of small roots

• Adventitious: where there is growth in an unusual area 

• Root hairs: small root       growth  

Stems• Stem: an organ of the plant that

support the leaves • Nodes: where stem and leaf attatch• Internodes: the segments of stem

between the nodes• Terminal bud: embryonic tissue

located at the tip/top of the plant• Axillary bud: the bud that is able to

form a branch • Apical Dominence: where the

growth of the main stem (the terminal bud) is dominant over the apical buds

http://users.rcn.com/jkimball.ma.ultranet/BiologyPages/A/apical_dominance.jpg

Leaf: organ that preforms photosynthesis• Petiole: joins the leaf to the stem• Blade: the flat part of the leaf• Vein: similar, but not as complex veins that are in

humans

Leaves

The Three Tissue Systems: Dermal, Vascular, and GroundTissue System: where one or more tissues interact as a functional unitDermal Tissue System• Epidermis: the outer protective layer

in plants • Periderm: another protective layer that

replaces the epidermis• Cuticle: the waxy coating

Vascular Tissue System• Xylem: cells (mainly dead) that move

H20 and minerals up from the roots • Phloem: transports sugar• Stele: the vascular tissue in stem and

root• Vascular cylinder: the tissue that forms

a column in the roots• Vascular bundles: the stele in leaves

and stems

Ground Tissue SystemServes as filler, support and storage• Pith: the ground tissue that is in the

vascular tissue• Cortex: external ground tissue to

the vascular tissue

 

Plant GrowthIndeterminate growth: continuous growth in plants (during entire lifetime) • Meristems: tissues that enable

plants to continuously grow      -  Apical meristem: at tips and roots• Primary growth: the plant grows in

length • Secondary growth: growth in

thickness (bark) (through lateral meristems)

• -Vascular cambian: secondary layers of vascular tissues

• -Cork cambian: where periderm replaces the epidermis (tougher)

Plant life• Annuals: die in a year.• Biennials: die in 2 years • Perennials: live many years...

Herbaceous: no wood (all primary growth)

Initials: the cells at the meristems that remain as meristems to continually produce new cellsDerivatives: cells that are produced by the apical meristems and become differentiated

Root Cap - protects the apical meristem as the root pushes through soil during primary growth.

Growth occurs in three zones of cells at successive stages of primary growth.

From the root tip up, the zones are cell division, elongation, and maturation

Primary Growth Lengthens Roots and Shoots

Primary growth roots produces the epidermis, ground tissue, and vascular tissue. 

Primary Growth of Shoots

leaves arise as leaf primordia, finger–like projections along the flanks of the apical meristem

Eudicot vs. Monocot

Eudicots - the vascular tissue consists of vascular bundles arranged in a ring. The xylem in each vascular bundle faces the pith, and the phloem faces the cortex. 

Monocot - the bundles are scattered throughout the ground tissue, rather than forming a ring (Figure35.16b ). In both monocot and eudicot stems, ground tissue consists mostly of parenchyma

 

Tissue Organization of LeavesThe epidermal barrier is interrupted by the stomata, which allow CO2 exchange between the surrounding air and the photosynthetic cells inside the leaf. stoma - the stomatal pore consisting of a pore flanked by two guard cells

Secondary growth adds girth to stems and roots in woody plants

Secondary growth, the growth in thickness produced by lateral meristems, occurs in stems and roots of woody plants. 

The secondary plant body consists of the tissues produced by the vascular cambium and cork cambium. 

The Vascular Cambium and Secondary Vascular Tissue

The vascular cambium is a cylinder of meristematic cells one cell thick. In this way, it is primarily responsible for the thickening of a root or stem.

In a typical gymnosperm or woody eudicot stem, the vascular cambium forms in a layer between the primary xylem and primary phloem of each vascular bundle

heartwood - the older layers of secondary xylem no longer transport water and minerals (xylem sap).sapwood - The outer layers still transport xylem sap.

Heartwood is generally darker than sapwood because of resins and other compounds that clog the cell cavities and help protect the core of the tree from fungi and wood–boring insects.

Plant Body Production: Growth, Morphogenesis, and Differentiation

• Morphogenesis: The development of body form and organization. It's all about gene expression and gggrrrrrrowth!

• Systems Biology: An approach to studying biology that aims to model the dynamic behavior of the whole biological systems.

• The most commonly studied plant is Arabidopsis thaliana. o The entire genome has been

sequenced!o Mmm... Mustard

Growth

•  Growth: Cell division increases potential for growth, but it is growth that increases mass!

The plane of cell division affects the plantform:• Parallel to previous= single file of cells•  On multiple planes= cube.• Random= disorganized clump of cells.•  Asymmetrical Cell division: Uneven distribution of cytoplasm. Signals a key

event in development.

Growth

• Large vacuole: Water is 90% of growth.

• The plan of cell division is determined by the preprophase band.

• Orientation determined by cellulose microfibrils.

Morphogenesis and Pattern Formation

• Pattern formation: the development of specific structures in specific places.

• Positional Information: Signals to which genes regulating development respond, indicating a cell's location relative to other cells in an embryonic structure.

• Polarity: the condition of having structural differences at opposite ends of an organism.

Phase Changes=Plant Puberty!

• Phase changes: The morphological changes that arise from transitions from a juvenile phase to an adult phase.o usually changes in the

leaves and stems o juvenile meristems can

keep growing juvenile shoot's and leaves if a node forms... even after the apical meristem is mature!

 •   •  

Genetic Control of Flowering

• Meristem identity genes

• ABC Model