Lecture 12 Plant Sciences/ Physiology Flashcards
What is the outer cell wall of a plant cell made of?
Cellulose- a strong substance able to withstand the pressure of moving fluids and nutrients without expanding
Comment on the role of transport proteins within the cell membrane.
Transport proteins aka carrier proteins located within the cell membrane, form a channel to allow substances such as sodium, potassium, sugars, proteins and messenger molecules to pass through. They make every from communication to cellular metabolism possible.
Why are chloroplasts so important?
Chloroplasts are the organelles where photosynthesis take place. They contain the pigment chlorophyll which is necessary for photosynthesis. Chloroplasts also store nutrients (starches).
Why is it important to avoid plants wilting?
Wilted plants rapidly lose nutrients. Harvesting, drying and storing plants is an art that aims to prevent the loss of nutrients and medicinal properties. Plants are best dried in a warm, dry place, or in the sun, then stored in cool dark place.
How can you naturally boost your magnesium consumption?
Eat leafy greens. Plant cells contain a green pigment, chlorophyll which is a valuable source of magnesium.
What are some of the benefits of consuming pectin?
Pectin is contained in a layer of cells in the middle lamella and glues cells together thus making them more stable.
Pectin has demulcent properties which heal the gut lining and bind to toxins and cholesterol (preventing absorption).
Thickens jams making them jelly-like
What type of tissue is chiefly responsible for growth? Describe the different types.
Meristemic tissue is rapidly dividing
Two types: apical and auxiliary
Cork Cambium- tube of meristemic tissue runs length of roots and stems in outer layer of woody plants, thickens
Lateral meristem- tube along roots and stems causing widening/ secondary growth
What is meant by Parenchyma? What are the different types.
Parenchyma are tissues with the following attributes:
thin-walled
unspecialised
abundant
rapidly-diving
adaptable to various f(x)’s via differentiation
Chlorenchyma- contains chlorophyll
Collenchyma- flexible support
Schlerenchyma- nut shells, fibers structural support
Aerenchyma- pockets of air in cells allowing for gas exchange. Common in aquatic plants
Describe the function of the following types of parenchyma:
Chlorenchyma
Collenchyma
Schlerenchyma
Aerenchyma
Chlorenchyma- photosynthesis
Collenchyma- gives flexible support (celery)
Schlerenchyma- strong structural support like in nut shells including fibres
Aerenchyma- have pockets of air allowing for gas exchange and flotation in aquatic plants
What are the functions of Xylem?
Xylem is a complex plant tissue that forms part of the circulatory system for the plant it is centrally located and transports fluid up the roots. Walls are reinforced with lignin and there are no end-walls between cells.
Found in roots, stems, leaves
What are the functions of Phloem?
Phloem forms part of the circulatory system of the plant. It is located peripherally to the xylem and consists of large tube-like cells with pores in end sieve plates, allowing cytoplasm to pass freely.
Transports glucose from leaves to all cells
Lose nuclei at maturity and depend on a smaller companion cell to regulate activity hence always found as a double cell.
What is the function of the Epidermis?
The Epidermis is a protective outer covering modified by environment
Normally one cell thick but may be several layers to prevent desiccation
Secrete cutin which forms a protective cuticle
Why is sap important to us?
Sap is the substance transported by the xylem carrying minerals and important antiseptic medicinal properties
In woody plants the epidermis is replace by ______. The waxy substance _____ dies leaving a bark layer.
Periderm
Suberin
________lack suberin and allow for gas exchange with interior of the stem.
Lenticels
What is important about Osmosis for plants?
What force balances “osmotic potential”?
Osmosis is how plants draw water and nutrients into and out of cells to keep themselves alive and growing.
Turgor pressure- the pressure exerted by water in a cell against a cell wall
What is meant by Transpiration?
Transpiration is the loss of water by evaporation from plants from leaves and lenticels into the atmosphere.
It is a cooling mechanism that increases with temperature.
Up to 1000L of water may be transpired daily by mature trees in hot summer months
What is the function of the Casparian Strip?
A single layer of waterproof waxy suberin-impregnated cells that form a regulatory barrier in the endodermis that forces fluids to pass through plasma membranes of cells and also filters out harmful substances.
What causes the droplets to appear on Lady’s Mantle leaves?
Guttation describes the process whereby water is forced out of leaves due root pressure.
When is the best time of day to harvest plant material and why?
After the morning dew but before the heat of the sun to prevent loss of fluids and essential oils.
What are stomata? What special type of cells are associated with this plant structure?
Stomata are openings found in leaves and stems where water exits and carbon dioxide and oxygen can diffuse.
Guard cells surround stomata by pairs. When turgid by the inflow of water, the stomata opens. When flaccid stomata close thus preventing water loss at night or drought.
What is another name for plant hormones?
Phytohormones
In which plant tissue are Auxins produced?
Auxins are produced in the apical meristem at the tips of shoots in plants
Why is Gibberellic acid important particularly in medicinal herbs?
GA causes cell elongation, cell division and lengthening of internodes and rapid stem growth.
Emphasis on vegetative growth over fruiting and provides prolific leafy material for herbal use.
Do you think the use of hormones in horticulture and agriculture is safe?
No, synthetic GA used in commercial fruit to increase the size of table grapes and regulate citrus flowering and rind maturation, is shown to cause cancer in animal tests.
We don’t know enough about Nature to interfere at the level of hormones
.
Which plant hormone causes leaves to die and fall?
Abscisic acid
Explain why many plants grow in a cone shape.
Auxins in the apical tip, stimulate ethylene (a growth inhibitor) production which inhibits ancillary bud growth. But as it goes down, growth is allowed to go out again. Typical Christmas tree shape.