SYSTEMATICS GRP 3: PLANT ANATOMY, PHYSIOLOGY AND EMBRYOGENESIS

plant anatomy

the study of the tissue and cell structure of plant organs

plant physiology

the study of metabolic processes in plants

cell wall

covering the outermost layer of a cell; present only in plants, and in some fungi, bacteria, algae

primary cell wall

closest to the inside of the cell and is the first formed cell wall

middle lamella

Outermost layer and it acts as an interface between the other neighboring cells and glues them together

secondary cell wall

Formed inside the primary cell wall once the cell is completely grown

cell membrane or plasma membrane

- outermost covering of the plant cell.
- controls both the entry and exit of both solute and solvent between the cell and the environment.

cytoplasm

rich, semifluid material present in cells of organisms that are closed off by the cell membrane

nucleus

- control center of the cell is often the largest organelle in the cell.
- contains the genetic information of the cell

- nuclear envelope
- nucleoplasm
- nucleolus
- nuclear pores

4 major parts of nucleus

chromatin/nuclear net

complex of DNA and proteins (histones) within the nucleus that condenses to form chromosomes during cell division

chromosomes

DNA-containing structures of eukaryotic nuclei that form during the process of cell division

chloroplast

large organelles and their function is the formation and storage of carbohydrates from photosynthesis

mitochondria

- ovoid, granular, filamentous, or sausage-shaped bodies which are abundant in cytoplasm.
- major site of ATP and energy production in plants

endoplasmic reticulum

the cross section appears as two parallel membrane systems of branching, intercommunicating tubules sacs also called cisternae, extending from the outer nuclear membrane to the plasma membrane

rough ER

outer surface exposed to the cytoplasm where ribosomes are attached

smooth ER

inner surface without ribosomes, concerned with fat or lipid synthesis

ribosomes

- small, spherical, or granular bodies that are visible only with the use of an electron microscope.
- main site for protein synthesis, especially enzymes and are believed to be the seat of protein synthesis

golgi apparatus

a stack of smooth cisternae (membrane-bound spaces) piled on each other. These plate-like flattened plate-like membrane-bound sacs contain tubules and have vesicles protruding from their margins

vacuole

- used for compartmentalizing cellular contents and for controlling some waste products.
- also important for maintaining cell turgor and for cell expansion

plasmodesmata

- membrane-lined pores which run through the cells.
- allows communication between cells

apical meristem

- a region of active cell division that produces new cells.
- these cells divide, expand, and differentiate into various cell types, forming the plant's tissues. This process, known as primary growth, results in lengthening of the plant

dermal tissue system

- Composed primarily of dermal cells, which are squat, cubic cells.
- Contains guard cells around stomata, trichomes (hair-like structures), and root hairs.
- The cuticle (a waxy layer) covers the outer surface of stems and leaves, protecting against water loss and pathogens

xylem

Transports water and minerals. Composed of vessel elements and tracheids

phloem

Transports photosynthates (sugars) throughout the plant

sieve cells

transport sugars, and companion cells assist with metabolic functions

parenchyma

Thin-walled cells, often involved in storage and photosynthesis

collenchyma

Cells with unevenly thickened walls for flexible support

sclerenchyma

Cells with lignified walls providing structural support

fibers

Long, slender sclerenchyma cells

sclereids

Irregularly shaped sclerenchyma cells

secondary growth

In woody plants, ___ increases girth and is produced by lateral meristems

vascular cambium

a cylinder of meristematic tissue that produces secondary xylem (wood) and secondary phloem, enhancing structural support and water conduction

cork cambium

replaces the outer dermal layer with a protective layer called cork, which forms the bark

stem

Support the plant, positioning leaves for optimal light exposure and holding flowers and fruits

primary growth

stems are initially formed by the apical meristem

vascular cambium

a layer of lateral meristem—adds layers of secondary xylem (wood) and secondary phloem to the stem

cork cambium

As the stem thickens, the outer dermal layer is replaced by cork tissue, which is produced by the ___

bark

Cork cells create a protective outer layer, known as the ___

leaves

Primary sites of photosynthesis in most plants, using sunlight to convert carbon dioxide and water into glucose (energy) for the plant

epidermis

outermost layer of cells, covered by a waxy cuticle that helps reduce water loss

stomata

small openings scattered across the leaf surface, allowing gas exchange (CO₂ in, O₂ and water vapor out)

guard cells

control the opening and closing of stomata, helping the plant regulate water loss and gas exchange in response to environmental conditions

mesophyll

internal tissue, mainly composed of parenchyma cells

palisade mesophyll

Elongated cells, packed with chloroplasts, where most photosynthesis occurs

spongy mesophyll

Loosely arranged cells with air spaces that facilitate gas exchange

vascular bundles (veins)

Each leaf has a network of ___ containing xylem (to transport water and minerals) and phloem (to carry sugars produced by photosynthesis)

roots

Anchor the plant, absorb water and essential nutrients from the soil, and often serve as storage for food reserves

root cap

A protective layer at the tip of the root, shielding the meristematic cells

apical meristem

Located just behind the root cap, this region is where active cell division occurs

root hairs

Extensions of epidermal cells that significantly increase the surface area for water and nutrient absorption

cortex

The outer layer of ground tissue, made of parenchyma cells that often store starch and other nutrients

endodermis

A selective barrier surrounding the vascular cylinder. The endodermis regulates the movement of water and nutrients into the plant's vascular system

plant embryology

- is the study of the origin and formation of new plants.
- it addresses the creation of sex cells, fertilization, and the generative sphere.
- it reveals the genetic and environmental factors that affect plant development
- it can be used to better understand plant evolution and to guide conservation efforts

- seed coat
- cotyledons
- endosperm
- one embryo

a normal seed consists of : ___ (4)

embryogenesis

embryo develops through a process known as ___, refers to the formation of an embryo from a zygote

- proembryo stage
- globular stage
- scutellar stage
- coleoptilar stage

stages of monocot embryogenesis (4)

proembryo stage

- Following fertilization, it undergoes asymmetrical cell division, resulting in an apical and basal cell.
- The apical cell divides more rapidly than the basal cell and finally becomes the embryo

globular stage

- the proembryo resembles that of dicots, but the suspensor is less differentiated and not in a single or double cell row.
- an outer epidermal layer forms, and a rapidly dividing cell group develops on one side, which will form the embryo axis

scutellar stage; scutellum

- a remnant of the cotyledon is visible.
- monocots have reduced the two cotyledons found in dicots to a single, modified cotyledon called the ___, which serves as conductive tissue between the endosperm and the embryo axis

coleoptilar stage

the embryo axis differentiates into the plumule (shoot) and radicle (root). In monocots, specialized tissues—the coleoptile around the shoot and the coleorhiza around the root—assist in emergence during germination

- proembryo stage
- globular stage
- cotyledon stage
- mature stage

stages of dicot embryogenesis

proembryo stage

- After fertilization, the egg and sperm nuclei form a proembryo, dividing into an apical and basal cell.
- The basal cell forms the suspensor, a column of cells that pushes the proembryo into the embryo sac and transfers nutrients

globular stage

- Basal cell derivatives form the hypophysis, which later develops into the radicle.
- Tissue differentiation begins to appear in the 16-celled globular embryo

cotyledon stage

- Cotyledon primordia become evident in the heart-shaped stage of embryogenesis, elongating to form a typical torpedo stage embryo.
- During the heart and torpedo stages, the embryo organizes to develop an apical meristem,
radicle, cotyledons, and hypocotyl

mature stage

- The embryo is fully formed, with easily visible separate cotyledons and distinct shoot and root meristems. The suspensor and basal cell begin to disappear at this point