Unit 6 Flashcards
What is the equation for photosynthesis
Carbon dioxide + water=glucose + Oxygen
what are the factors that affect photosynthesis
1.reduced concentration of air molecules causes lower rate of concentration. eg top of mountain so less co2
2. the reactions in photosynthesis are catalysed by enzymes that work better at warmer temps.
3.light intensity
what is a limiting factor
a factor that prevents a rate from increasing
what are palisade cells
they are near the top of the leaf and packed with chloroplasts these adaptations allow the leaf to absorb a great deal of light
what is a stomata
carbon dioxide for photosythesis comes from the air. leaves contain microscopic pores called stomata (singular stoma)
stomata allow the carbon dioxide to diffuse into the leaf. the stomata are oped and closed by specialised guard cells. in the light the stoma are opened by these specialist cells in the dark closed.
what is osmosis
is when solvent molecules (water) diffuse through a semi permeable membrane. they diffuse from where there are more of them to where there are fewer. high to low concentration.
what is a tropism
responding to a stimulus by growing towards or away from it.
What is a phototropism
A tropism caused by light. plant shoots are phototropic so the plant hets enough light for photosynthesis
what are auxins in roots
In roots, auxins cause cells to stop elongating and this causes positive gravitropism- growth towards direction of gravity. It helps roots to anchor the plant in place and reach moisture underground.
how can artificial auxins be used in weedkillers?
artificial auxins make some plants grow uncontrollably which can kill them.
selective weedkillers contain artificial auxins to kill plants with broad leaves but not those with narrow leaves. therefore weeds can be killed without affecting a crop.
what are gibbererellins
they are plant hormones that are naturally released inside a seed to start germination. some seeds need a period of dark or cold before they can germinate but plant growers can use gibbererellins to make the seeds germinate without this.
what is photoperiodism
that are plant hormones that are the response of an organism to the number of daylight hours in a day. some plants use this to flower at a certain time.
How is ethylene a hormone gas
fruit producers often pick unripe fruit and ripen it when needed with ethene hormone gas
makes sure fruit reaches the shop in a just ripe condition
how are auxins used in rooting powder
the auxins cause plant cutting to develop roots quickly
large numbers of identical plants can be grown quickly using cuttings compared to growing plants from seed
what is xylem
The xylem is a tissue which transports water and minerals from the roots up the plant stem and into the leaves.
Xylem consists of dead cells. The cells that make up the xylem are adapted to their function:
1.They lose their end walls so the xylem forms a continuous, hollow tube.
2.They become strengthened by a substance called lignin
. Lignin gives strength and support to the plant. We call lignified cells wood.
Transport in the xylem is a physical process. It does not require energy.
