lecture 11 Flashcards
basic plant organs
- the plant body contains three basic organs:
- roots, stems, and leaves
- each of these organs are composed of different tissues
- the organ structure correlates nicely with function
- plants must draw water and minerals from soil and water and CO2 from the environment
- plant root and plant shoot cannot survive without one another
root system
- anchors the plant in soil
- absorbs ad transports minerals and water
- stores food
- near the root tips there is an abundance of root hairs
- increases surface area
shoot system
- made of stems and leaves
- also reproductive structures such as flowers
- stems: generally above ground
- support leaves and flowers
- nodes: point at which leaves are attached
- internodes: portions of the stem between the nodes
- leaves: main photosynthetic organs
- composed of a flattened blade and a stalk called a petiole which joins the leaf to the node of the stem
two types of buds
terminal buds
axillary buds
buds
terminal buds: at the apex tip of the growing stem
-has developing leaves and a compact series pf nodes and internodes
axillary buds: these are within the angle between the leaf and the stem
-usually dormant
-hormones produced by the terminal buds inhibit their growth-this is called apical dominance
-concentrating resources toward growing taller increases the plants exposure to sunlight, important when vegetation is dense
-under some conditions the axillary buds begin to grow and removing the terminal bud often stimulates the growth of the axillary bud
3 modified root stems
horizontal stem (runner)
rhizomes
bulbs
horizontal stems
grows along the ground surface
- allows plant to reproduce asexually
ex) strawberry plant
rhizomes
horizontal stems that grow either right below or along the surface of the soil
- they store food and may also spread and form new plants
- potato plants have rhizomes which end in enlarged structures called tubers which are specialized for storage (the potato)
bulbs
underground shoots which contain swollen leaves for food storage
modified leaves
tendrils
spines
tendrils
the tips are coiled around a stem
-this helps the plant to climb such as in a grapevine
spines
spines of a cactus are a modified leaf that protects against being eaten by animals
three main plant tissues
-tissue: group of cells with common structure, function or both
tissue system: composed of one or more functional units within a plant
-the plant root system, stem and leaf are all made of three tissue systems:
1. dermal tissue
2. vascular tissue
3. ground tissue
-three tissue systems have different arrangements in different organs
dermal tissue system
- forms an outer protective covering
- first line of defense against physical damage and infectious organisms
- consists of:
- epidermis: single layer of tightly packed cells
- cuticle: waxy outer covering atop the epidermis, protects against waste loss
vascular tissue
- composed of xylem and pholem tissues
- provides support and long distance transport