chapter 5

what cells need to function

• obtain nutrients and oxygen

• remove waste and toxic substances

• stable regulationg of conditions such as temperature and pH

unicellular

life is composed of a single cell (bacteria)

multicellular

organisms are made up of specialised cells that contribute to forming tissues, where tissues are groupings of cells that work together to carry out particular functions

cells

smallest functional unit of a living organism

tissues

cluster of cells which perform a shared function

• for some organisms, tissues are the greatest levels of organisation required to meet survival and reproduction needs

organs

composed of a combination of multiple tissues and cells taht perform specialised tasks

• organs and tissues form larger systems

systems

collections of organs and tissues performing vital functions for the survival of organisms

organisation of plants

• organised into dermal tissue that lines the outside of plants

• vascular tissue that is responsible for transporting water and nutrients around the plant

• ground tissue; described all other tissues in a plant

vascular plants

contain vascular tissue

• transport water and minerals throughout the plant

  • xylem tissue and phloem tissue

non-vascular plants

• moss

do not contain vascular tissue and only require simplified tissues to function

plant tissues

dermal tissue - single layer of cells covering the outside of a plant

• secretes waxy substance called a cuticle to form a physical barrier between a plant and its environment to reduce water loss and physical damage

ground tissues - make up majority of interior of the plant and carry out metabolic functions

vascular tissues - run through ground tissue of vascular plants, carrying water and nutrients

plant organs

leaves, flowers, fruits, stems and roots

root system

• typically undergound

• absorbs water and nutrients from the soils

• provides plant support and structure

shoot system

• angiosperms, made up of reproductive and non-reproductive sections

• reproductive sections = flowers and fruits

• non reproductive sections = leaves and stems

animal tissue

muscle, nervous, connective, epithelial

• skeletal, cardiac and smooth

vascular tissue in plants

transports water, nutrients and minerals

• xylem tissue - tubes that transport water in one direction from the roots to the leaves of the plant

• phloem tissue - tubes that transport sugars and other nutrients around the plant in both directions

dicots

vascular tissues are located in bundles in the centre of roots and just below the bark of stems and trunks

roots

abosrb water and nutrients from the soil

• diffusion occurs at a greater rate

many diff branches, increasing overall SA for absorption

• root hair cells, finger like projections

extracellular pathway

the pathway by which roots absorb the majority of the water from the soil

• apoplastic route

• water diffuses into roots in the gaps between cells

  • once casparian strip reached, water and solutes are forced to enter cells

cytoplasmic pathway

pathway by which roots absorb the majority of nutrients and essential minerals from the soil

• symplastic route

• mineral ions either passively diffuse into the cytoplasm or are taken up via active transport in root hair cells

  • concentration of ions within cytoplasm of root hair cells in 100x greater than concentration of similar ions in groundwater and soil

casparian strip

impermeable barrier between root cells and vascular tissue that forces water and solutes travelling by extracellular pathway into cytoplasm of cells

structure of xylem tissue

long, skinny tubes that run from roots to shoots of plants

• made of vessel elements and tracheids

  • hollow cells, lignified cells and pits

• vessel elements and tracheids differ by their size and arrangement

phloem tissue structure

long, skinny tubes that run throughout a plant; made of non-lignified living cells

• sieve cells and companion cells

  • hollow cells, tube-like structure, sieve plates and pits between sieve cells

• companion cells which regulate the entry of nutrients into the phloem

transpiration

water and nutrients move up the xylem, 1% of water from xylem is used during photosynthesis

• majority of the remaining water evaporates and exits a leaf via stomata during gas exchange

• movement of water up the xylem and exit via stomata is passive process of transpiration

• assists in photosynthesis

• helps plants regulate heat and water balance, distribute nutrients throughout the plant

• prevent wilting and cell damage

cohesion in transpiration

air pressire in leaf becomes lower than pressure in roots

• lower pressure creates a force that draws water up from xylem

• water like to stick together so more water is drawn up

adhesion in transpiration

capillary action helps water flow in xylem

• caused by adhesion of water molecules to surface of xylem

• same force causes a meniscus to crawl up side of a test tube, in small enough tubes, force is large enough to pull the water up a tube

translocation

movement of nutrients created in the leaves to other areas of the plant, taking place in the phloem from a source to a sink

1. glucose produced in leaf cell, pumped into companion cell, diffused into sieve cells of phloem

2. increased concetration in sieve cells —> water diffuses from xylem, increased turgor pressure in sieve cells

3. increase in turgor pressure pushes liquid in phloem throughout the plant, glucose is actively transported into required cells

4. glucose in unloaded in sink cells, concentration in phloem reduced, water will difffuse back into xylem

environmental conditions that affect transpiration rates

temperature - high temp = more water evaporates

light - high light = stomata opens, increasing amount of water lost to transpiration

humidity - humidity increase = less water evaporate in air

wind - calm days = water released from stomata stays near, windy = humid layer blown away

water availability - high = roots absorb more water