biology chapter 29 - plant form

indeterminate growth

add structures to their bodies throughout their lives in response to environmental change

where do roots and shoots grow?

at their tips

shoot system

• made up of components for growth (the vegetative shoot of a stem and leaves)

• and reproduction (reproductive shoot that produces reproductive structures)

where is the principal site of photosynthesis?

leaves

what features of leaves are vital in plant’s ability to absorb light?

arrangement, size, etc.

what is included on the repeating unit of the vegetative shoot?

• internode

• node

• leaf

• axillary bud

• NO reproductive structures

what does the axillary bud contain that allows the plant to branch or reproduce the main shoot?

meristematic tissue

• 🌱 Form branches → the axillary bud grows into a new shoot

• 🌱 Replace the main shoot → if the main shoot is damaged or eaten, an axillary bud can grow and take over

vegetative axillary bud

vegetative shoot repeating unit

the basic section of a plant’s shoot that repeats as the plant grows.

internode

the stem section between nodes

node

the point where leaves attach

leaf

captures sunlight for photosynthesis

axillary bud

a small bud located where the leaf meets the stem

• a product of the primary shoot apical meristem and itself contains a shoot meristem

• frequently develop into branches with leaves, and may form flowers

axillary buds can change what they produce depending on what stage the plant is in.

• During vegetative growth: 🌱
  A vegetative axillary bud can grow into a new shoot, essentially recreating the main/primary shoot with stems and leaves.

• During reproductive growth: 🌸
  Once the plant switches to its reproductive phase, axillary buds can instead develop into flowers or floral shoots.

axillary buds during vegetative growth

A vegetative axillary bud can grow into a new shoot, essentially recreating the main/primary shoot with stems and leaves.

axillary buds during reproductive phase

axillary buds can instead develop into flowers or floral shoots.

3 types of tissue make up

roots, shoots, and leaves

dermal tissue

composde primarily of the epidermis, a protective outer covering of the plant

ground tissue

several cell types tht function in storage, support, photosynthesis, and secretion

vascular tissue

cell types for conducting fluids and dissolved substances through the plant body.

microtubules

• tiny structures inside the cell that act like guides/tracks.

• They line up in a particular direction inside the cell.

• They guide where cellulose fibers are deposited in the cell wall.

• Cellulose fibers provide strength and resist expansion.

cells that support the plant body…

have more heavily reinforced cell walls with multiple layers of cellulose and other strengthening molecules, including lignin and pectin.

meristems

clusters of small, undifferentiated cells with dense cytoplasm and proportionately large nuclei. areas of active clel growth and differentiation

meristems division

produce a copy and a differentiated cell

apical meristems

generate primary growth, growth from the tips of plant, including tips of stems and tips of roots (all plants experience)

axillary meristems

meristems that occur at the node where a branch of lead meets the main stem

primary tissues

tissues derived from apical meristems (growth from shoot and root apical meristems)

primary plant body

the portion of a plant formed through [primary growth by apical meristems

the 3 tissue systems apical meristems give rise to (sometimes 4)

• protoderm - (dermal tissue) produces the epidermis, a protective outer covering of the plant

• procambium (vascular tissue) - produces primary vasculature for water mineral transport (primary xylem) and organic nutrient transport (primary phloem)

• ground meristem (ground tissue) - produces ground tissue often used in support.

  • Forms parenchyma, collenchyma, and sclerenchyma.

  • Functions in photosynthesis, storage, and support.

• intercalary meristem - a region of actively dividing cells located between mature tissues, usually near the base of leaves or internodes. (sometimes)

protoderm

dermal tissue produces the epidermis, a protective outer covering of the plant

procambium

(vascular tissue) - produces primary vasculature for water mineral transport (primary xylem) and organic nutrient transport (primary phloem).

ground meristem

• (ground tissue) - produces ground tissue often used in support.

  • Forms parenchyma, collenchyma, and sclerenchyma.

  • Functions in photosynthesis, storage, and support.

intercalary meristem

a region of actively dividing cells located between mature tissues, usually near the base of leaves or internodes. (sometimes)

lateral meristems

generate secondary growth (only some plants)

secondary growth

growth in the sideways direction (width/thickness)

two types of lateral meristems that produce secondary growth

• vascular cambium - produces new vascular tissue (xylem and phloem)

• cork cambium - produces new layers of cork

vascular cambium

produces new vascular tissue (xylem and phloem)

cork cambium

produces new layers of cork. also a type of lateral meristem formed from ground tissue that contributes to the outer bark of a tree.

herbaceous plants

plants with fleshy, not woody, stems

what is the main component of wood?

secondary xylem

secondary phloem is…

very close to the outer surface of a woody stem

secondary tissues

tissues formed from lateral meristems, which comprise most of the trunk, branches, an older roots of trees and shrubs

secondary tissues are collectively called…

secondary plant body

dermal tissue derived from an embryo or apical meristem forms the…

epidermis

epidermis

the single, outermost layer of cells that covers the primary plant body, including leaves, stems, roots, flowers, seeds. 1 cell layer thick

cuticle

insoluble layer that covers epidermis, which functions to limit the movement of water into or out of the plant. composed of a polyester polymer called cutin and a variety of waxes

cutin

waxy, water-resistant substance found in the walls of plant epidermal cells.

guard cells

paired, sausage shaped (in eudicots) or dumbbell shaped (in monocots) cells flanking a stoma (mouth-shaped epidermal opening). have chloroplasts.

stomata

occur in the epidermis of leaves and occasionally on other parts of the plant

serve a dual function

• exchange of oxygen and carbon dioxide gasses through stomata (essential for photosynthesis)

• diffusion of water in vapor form takes place almost exclusively through the stomata, enabling transport of water and minerals from the roots to the leaves

• often more numerous on the lower than upper epidermis, reducing water loss

• some are the opposite, to maximize gas exchange

two functions of stomata

• transport of water and minerals from roots to leaves

• exchange of oxygen and carbon dioxide

root hairs

tubular extensions of individual epidermal cells, occur in a zone just behind the tips of young, growing roots. greatly increase the root’s surface area

parenchyma cells

most common type of plant cell

• large vacuoles and thin walls

• have living protoplasts, push up against each other shortly after they’re produced and assume other shapes, ending up with 11 - 17 sides

• may live for 100+ years

• most abundant cells of primary tissues and sometimes are in secondary tissues

• have functional nuclei and are capable of dividing, and they usually remain alive after they mature

• 
  

BRIGHTER DAYS AHEAD

BRIGHTER DAYS AHEAD

sclerenchyma cells

have tough, thick walls

• their secondary walls are often impregnated with lignin, a highly branched polymer that makes cell walls more rigid; for example it is an important component of wood

lignin

common in the walls of plant cells that have a structural or mechanical function

vascular tissue makes up…

two types of conducting tissue

• xylem - water and dissolved minerals

• phloem - conducts a solution of carbs. also hormones, amino acids, and more

xylem transports…

water and dissolved minerals

phloem transports…

conducts a solution of carbs. also hormones, amino acids, and more

xylem

usually contains a combination of vessels and tracheids

• vessels - continuous tubes formed from dead, hollow, cylindrical cells arranged end to end

• tracheids - dead cells that taper at the ends and overlap each other

vessels

continuous tubes formed from dead, hollow, cylindrical cells arranged end to end

tracheids

dead cells that taper at the ends and overlap each other

transpiration

diffusion of water vapor from a plant

• happens in some plants.

• tracheids are the only water conducting cells present; water passes in an unbroken stream through the xylem from the roots up through the shoot and into the leaves. when the water reaches the leaves, much of it diffuses in the form of water vapor into the intracellular spaces and out of the leaves into the surrounding air, mainly through the stomata.

• vessels appear to conduct water more efficiently than do the overlapping strands of tracheids

4 regions recognized in developing roots

1. root cap

2. zone of cell division

3. zone of elongation

4. zone of maturation

root cap

a thimble-shaped group of cells located at the very tip of a plant root that protects the delicate growing tissues underneath as the root pushes through the soil.

• cells in outer root cap secrete a slimy su stance produced by golgi bodies

• root cells have an average life of around a week

• the slimy mass also provides a medium for the growth of beneficial nitrogen fixing bacteria in the roots of plants such as legumes

• a new one is produced if the old one is removed

• can sense which direction gravity is pulling

• inside are specialized cells called columella cells

columella cells

specialized cells located at the tip of a plant's root cap that function as the primary site for sensing gravity (graviperception).

• Contain amyloplasts, which are plastids filled with starch

• because amyloplasts are relatively heavy, gravity causes them to settle toward the bottom of the cell

• root bends in the direction gravity is coming from

  • CALCIUM IONS IN amyloplasts INFLUNECE distribution of the growth hormone auxin in the cells

  • however, bending is seen in the absence of auxin, so probably impacted by multiple signaling mechanisms

zone of cell division

• cells are small, cube shaped, have small vacuoles, and large nuclei

• dividing rapidly by mitosis

• the daughter cells produced by apical meristems

zone of elongation

• cells stop dividing rapidly and grow larger and longer

• no further increase in cell size will occur after this

• only increase in girth

zone of maturation

where cells become specialized

• cells of the root surface cylinder mature into epidermal cells (very thin cuticle and include both root hair and nonhair cells)

• root hairs not visible until this stage of development

• endodermal primary walls - the first-formed cell walls of endodermal cells in a root

• endodermis - layer of cells surrounding the vascular tissue

• the primary walls contain suberin, a fatty, water proof substance

• suberin forms bands called caspian strips, which block water and substances from moving between endodermal cells through the cell walls

• therefore, water and minerals have to enter the endodermal cells and cross their plasma membranes, which are selectively permeable

endodermal primary walls

the first-formed cell walls of endodermal cells in a root

endodermis

layer of cells surrounding the vascular tissue

suberin

a fatty, water proof substance found in endodermis walls

caspian strips

bands formed from suberin which block water and substances from moving between endodermal cells through the cell walls

pericycle

layers of cells just inside the endodermis of a root

• produces lateral roots

in eudicots and other plants that undergo secondary growth

1. some cells from the pericycle and some parenchyma cells between the xylem and phloem become the vascular cambium

2. the vascular cambium starts producing new vascular tissue

   1. secondary xylem - towards the inside

   2. secondary phloem - towards the outside

3. as more secondary xylem and phloem are produced, they form concentric cylinders around the root

in woody plants, some cells of the pericycle become…

cork cambium (produces tissues that make outer bark)

as the roots thicken….

the og tissues outside the stele (vscular cylinder) get crushed and eventually dissapear, get replaced by bark

taproot system

a single large root with smaller branch roots

fibrous root system

many smaller roots of similar diameter

haustoria

stems of certain plants that lack chlorophyll and produce peglike roots that penetrate the host plants around which they’re twined. establish contact with the conducting tissues of the host and parasitize their host

food storage roots

the xylem of branch roots have many extra parenchyma cells that store larger quantities of carbohydrates

buttess roots

some tropical trees that produce huge roots toward the base of the trunk, providing stability

shoot apical meristem

the growing point at the tip of the stem

produces

• stem tissue

• leaf primordia

leaf primordia

young structures that develop into leaves

• can change into a floral meristem

phyllotaxy

the pattern/arrangement of leaves around a stem (to optimize sunlight)

3 patterns

1. alternate/spiral - one leaf per node, with leaves around a stem

2. opposite - two leaves per node, directly across from each other

3. whorled - 3+ leaves on the same node, forming a circle around the stem

alternate/spiral pattern

one leaf per node, with leaves around a stem

opposite pattern

two leaves per node, directly across from each other

whorled pattern

3+ leaves on the same node, forming a circle around the stem

golden ratio angle

137.5 degrees from previous leaf

axil

the angle between a leaf’s petiole (blade) and the stem

terminal buds

buds at the tip of the shoot. grow and make the shoot longer

protective winter bud scales

things some buds have that drop off and leave scars

vascular cambium growth

process that makes plants stem or root wider

in woody eudicots and gymnosperms…

a 2nd cambium, the cork cambium, arises in the outer cortex

adventitious roots

roots that grow from a stem or leaf instead of the main root system

bulbs

consist of fleshy leaves attached to a small, knoblike stem. for bulbs, next years leaves come from the tip of the shoot apex, which are protected by storage leaves

rhizomes

horizontal stems with long internodes that usually grow along the surface of the ground

runners

type of stolon, specifically grow strictly above the ground in a long, horizontal line

stolon

stem with long internodes (but no roots), that grows underground/specialized horizontal stem that grows along the soil surface to help plants reproduce asexually

tubers

enlarged underground plant structures that store nutrients and energy

when leaf primordia first appears…

not programmed to be a leaf! can develop into a new shoot.