Plant Development Flashcards
Vascular plants have 2 distinct organ systems
shoot system: stems and leaves and reproductive parts of the plant; above ground; light for photosynthesis
root system: plants absorts water water and minerals; underground
organs and tissues in plants
roots, stems and leaves; each include 3 tissues types (ground, vascular, dermal)
3 major functions of root system of seed plants
- anchoring plant to soil
- absorbing water/minerals and transporting them upwards
- storing products of photosynthesis - some can absorb moisture and exchange gases - usually underground
2 types of root systems
tap root systems: main root that grows down vertically, smaller lateral roots, deep into soil, good for dry soil plants, usually with dicots like dandelions
fibrous root systems: closer to surface, dense network, prevents soil erosion, usually monocots like grasses
root structures with evolutionary adaptions of specific purposes
bulbous roots - store starch
aerial roots and prop roots: above-ground that support additional anchoring
tap roots: some are for sugar and starch storage like carrots, turnips, beets
epiphytic roots: plants to grow on another plant
main function of stems (3-4)
- support to plant, holding leaves, flowers, buds
- connect roots to leaves
- transporting absorbed water and minerals from roots to rest of plant
- transporting sugars from leaves to desired locations throughout plant
4 types of stems
herbaceous - soft and greem
woody - hard and wooded
unbranches - single stem
branched - divisions and side stems
typical structures
nodes (point of attachment for leaves and flowers) and internodes (regions in between nodes)
tip of the shoot: apical meristem within the apical bud
auxilary bud: found in the area between the base of a leaf and stem where it can give rise to a branch of flower
reproductive shoot
flower
leaves
main site of photosynthesis - making food
green because of chlorophyll! but some leaves can have different colors with other plant pigments
petiole and veins
petiole: what attaches leaves to the plant stem
veins: vascular tissues like zylen and phloem through the leaves; also provide structural support
leaves changes to adapt to specific environments
coniferousplants of cold environments: smaller, needle leaves - small surface area and sunken stomata (gas exchange) for less water loss
– ex. cacti with spines and succulent stems
aquatic plants: leaves with wide lamina to float and thicker cuticle to repel water
2 types of plant tissue systems
meristematic tissue: undifferentiated like animal stem cells - continue to divide and growth of plant
permanent(non-meristematic): no longer actively dividing, meristems produce cells that quickly differentiate and become permanent tissues
3 main tissue types
dermal, vascular, ground
dermal tissue
protects the plant, gas exchange, water absorption; waxy cuticle to prevent evaporative water loss, stomatas for gas exchange, root epidermis don’t have waxy cuticle
root hairs - extension of root epidermal cells to increase surface area of roots and more absorption
trichomes - spiky outgrowths of epidermal tissue on stem and leaves which aid in defense against herbivores
types of cells: epidermal cells, guard cells - stomata, trichomes
ground tissue
different functions based on cell type and location
parenchyma - photosynthesis and storage in roots
collenchyma - shoot support of active growth
sclerenchyma - shoot support in areas of inactive areas
supportive matrix for vascular tissue, structural support, storage of water and sugars
vascular tissue
transport of water and nutrientss
xylem - water and nutrients from roots to different parts of plants plus structural support
phloem - food, organic compounds to other parts of plants
vascular bundle: xylem and phloem are adjacent to each other
cells: tracheids, vessel elements, sieve tube cells, companion cells
what all plants cells share
primary cell walls which are flexible and can expand as cell grows and elongates
some have secondary cell wall of lignin (wood) and inflexible for support
cells in dermal tissue
epidermal cells: make a single outer layer surrounding entire plant for protection and specialized adaptations in different organs; water and minerals absorption, root hairs
cuticles for less water loss except in roots
stomatas - openings for gas exchange while guard cells around each stomata control opening and closing of stomata
trichomes - reduce transpiration (loss of water), increase solar reflectance, and defend against herbivores
cells in vascular tissue, xylem and phloem
xylen and phloem (tissues)
vascular bundle is both xylem and phloem (in roots,called the vascualar stele or vascular cylinder) - in animals, the circulatory system are tubes lined with cells but vascular system are CELLS with substances moving through individual cells
xylem tissue: vessel elements and tracheids - tubular cells that conduct water - tracheids are in all vascular while angiosperms and few others have vessel
– have pits between adjacent cells for free flow of water; also lignin secondary cell walls; also dead when carrying water at functional maturity
phloem: sieve cells and companion cells - sieve cells conduct sugars through pores called sieve plates between cells; alive at functional maturity but no nucleus, ribosomes, or cellular structures - supported by companion cells which provide metabolic support and regulation
parenchyma, collenchyma, schlerenchyma, endodermis
parenchyma - most abundant and versatile cell type; flexible primary cell walls, most lack secondary; totipotent meaning they can differentiate into all cell types; responsible for rooting a cut stem; most tissues in leaves where photosynthesis occurs, large amounts of chloroplasts
– in roots, they are sites of sugar/starch storage “pith or cortex” - can also be associated with phloem cells as parenchyma rays
collenchyma - no secondary walls, thicker primary walls, stretch and elongate, structural support in shoot system, celery
schlerenchyma - lignin secondary wall, no stretching, structural support in mature stems after growth stops - dead at maturity
endodermis- specialized ground tissue in roots, checkpoint for materials to enter vascular system, the Casparian strip is waxy substance that forces water and solutes to cross through plasma membranes of endodermal cells instead of slipping between cells
dicot vs monocot tissue arrangement
roots: dicot xylen and phloem are in an X; eudicots have tap roots shape; monocot ina ring around the pith plus fibrous roots
stems: dicot vascular bundles in a ring while monocots are randomly scattered
leaves have palisade and spongy parenchyma cells with vascular tissues: monocots have parallel veins of vascular tissues while dicots have branched/net-like pattern in leaves
plant embryogenesis
zygote divides asymmetrically into an apical cell becomes the embryo while suspensor is like an umbilical cord
auxin: plant hormones across the ovule - higher auxin means apical!
CYTOPLASMIC DETERMINANTS!!
cotyledons, hypocotyl, radicle
cotyledons - embryonic leaves - first leaves upon germination
monocots have one; dicots have two
epicotyl: the part of the plant that grows above cotyledons
hypocotyl: future stem
radicle: embryonic roots become the future roots
determinate vs indeterminate growth
animals have determinate which grow to a specific body size and shape while plants will continue adding new organs as long as it has the resources
meristems
specialized tissues that are regions of continuous cell division and growth
- undifferentiated or incompletely differentiatied and can keep producing cells that can specialze and become permanent tissues
apical meristems
tissue at the tips of stems and roots which enable a plant to extend in length
lateral meristems
facilitate growth in thickness or girth of maturing plant
intercalary or basal meristems
only in some monocots; at bases of leaf blades and at nodes which enable monocot leaf blade to increase in length (think lawn grass even after mowing)
primary and secondary growth
taller/longer vs wider growth
primary: root apical meristems or shoot apical meristems
secondary growth: vascular cambium and cork cambium (lateral meristems)
not all plants show secondary growth
root cap
stryctyre that protects the root tip; exclusive to roots;
continuously replaced as roots push through soil
zones of root cap
zone of cellular division: apical meristem, cells are activiely dividing with mitosis
cellular elongation: newly formed cells are growing or increasing in length to add length to the root - water uptake stretches the cells!
cellular maturation: where newly elongated cells complete differentiation into dermal, vascular, or ground tissues (gene expression!)
lateral roots and pericycle
roots that branch from main tap root
originate from meristematic tissue in pericycle
once they emerge, display their own primary growth, continually adding length
are lateral roots primary or secondary growth?
primary growth in stems
result of rapidly dividing cells in the apical meristems at the shoot tip
primary growth in shoots - apical dominance
the influence that the apical bud has on overall plant growth
-prevents growth of axillary buds that form on the sides of branches and stems
secondary growth in shoots (and roots)
controlled by lateral meristems - vascular cambium and in woody plants, the cork cambium
herbaceous vs woody plants
herbaceous - mostly primary growth, not really thick
secondary growth: wood! occurs in some dicots, rarely in monocots
vascular cambium
between primary xylen and phloem within the vascular bundle
- cells of vascular cambium divide and form the secondary xylem and secondary phloem
vascular bundle positions of tissues
xylem towards the interior and phloem towards the exterior
secondary xylem and phloem
tracheids and vessel elements and sieve elements and companion cells – cells of secondary xylem contain lignin: xylem with pith - wood
cork cambium and cork cells
outermost lateral meristem, produces cork cells which contain a wax that repels water
phloem + cork cells = bark
periderm
cork cambium, cork cells, phelloderm (grows inward from cambium)
during growing season
a new layer of xylem and phloem are added each year
interior xylem layers eventually dies and filled with resin for structural support only
heartwood
interior, nonfunctional xylem - is heartwood associated with the idea that xylem vascular tissues are dead at functional maturity??
sapwood
newer, functional xylem
a mature tree’s layers
many interior layers of older, nonfunctional xylem deep within the stem, only a small amount of older phloem
annual growth rings
cells of secondary xylem have a large internal diameter and primary cell walls are not extensively thickened during spring growing season (early/spring wood)
during fall: secondary xylem develops thickened cell walls which makes late/autumn wood
– season decrease in vessel elements and seasonal increase in tracheids == results in a ring which can tell us the tree’s age and prevailing climatic conditions during each season
