Coordination and Control Flashcards
Phytohormones are known as ?
Plant hormones ( growth regulators )
Chemical messages are recognized as ?
Hormones ( meaning : to excite )
Auxin was named by ?
F.w. went
What is Tropism ?
Growth responses that result in curvature of whole plant organs away or towards stimuli
Tropism ( Tropos means ‘ turn’ )
✓phototropism ( light )
✓ gravity ( geotropism )
✓ Touch ( thigmotropism )
independent time measuring system is called ?
Biological clock
Living organisms when repeat their biological or behavioural activities at regular intervals. This behavior is called ?
Biological rhythms or biorhythms
When biorhythms occurs with in a frequency of about 24 hours . They are called ?
Circadian rhythm
E.g sleep movement of bean plants 🌵 even if it kept in constant light 🕯️ or constant darkness’s
What are endogenous movements?
Movement independent of external factors like light and temperature
The phenomenon in which the influence of day length on plants is studied is called ?
Photoperiodism
Responses to environmental stress 😬
Transpiration — produces cooling effect in plants by evaporation
✓Response to drought condition:
@ water 💦 content in soil becomes low … Water deficiency causes guard cells to lose turgor … Overcome by release of abscissic acid which keeps stomata closed .. plus Root growth 📈 also responds to drought by developing deeper root system
✓ Response to oxygen deficiency :
Aerial roots that provides excess of 02
✓Response to salt stress :
Halophytes have salt glands which pumps excess salt out from the plants ☘️🍀
✓ Response to heat stress :
✓Response to herbivory :
@ plants overcome excess herbivory — by developing thorns and production of distasteful or toxic compounds.
What are phytoalexins ?
Infected plants ☘️ produce variety of compounds called phytoalexins , an antibiotic , which destroys or inhibits the growth of microorganisms
Auxins ( To increase )
cell division and cell enlargement
✓Auxins are a class of plant growth substances both natural and synthetic first revealed by Went ( 1926 )
✓Indole acetic acid ( IAA )— synthesized at the apices of stem and root ( apical meristem)
Role of Auxin :
🍓
Gibberellins
✓ promotes cell division and cell elongation
✓ Gibberella fujikuroi fungus which infected rice seedlings and produced a disease bakanae ( foolish seedling )
✓ isolated by T.yabuta and T.Hayashi
✓ major sites of their production are roots , stems and leaves
✓ stimulate cell division
✓ cell elongation
✓ stimulate flowering 🌹🌺
✓ fruit 🍑🍓 development
✓ growth of pollen tube
✓ parthenocarpy
Cytokinin
✓ react with auxin to induce cell division ➗
✓ obtained from coconut 🥥🌴 milk , herring sperm DNA and yeast extracts
✓ naturally occurring cytokinin is zeatin ( obtained from immature corn grains 🌾🌽 )
✓ kinetin ( a synthetic cytokinin ) has same effects as that of zeatin
✓ initiate cell division in presence of auxin
✓ delayed senescence ( old age )
✓ break seed dormancy
✓ promote fruit development
Abscissic Acid
✓ growth inhibitor produced by plants ☘️ during adverse conditions such as drought condition and at the onset of winter .
✓ induces dormancy in buds and seeds
✓ causes stomata to close
✓ promotes senescence
