Module 5.5 Plants Flashcards
abiotic components
components of an ecosytem that are non-living .
menaing of alkaloids
organc nitogen containig bases h havre important physiological effcts on animals , includins nicotine and morphine .
what are biotic compoenents
component , of an ecosystem ,t ahtt are lviign .
what are phremone .
any chemical substances , released by one living thing , which infleuncnes the behavi our or pohysiology of another livig things
tannins
phenolic compounds located in cell vacuoles , or in surface wax on plants .
what is tropism
a directional growth response , in which the direction of the response is determined by the direction of the external stimulus .
how may a plant repond to changeing typies of stimuli
responding to the enviornemnt may help plant to surviv elong enough to reporduce , in highee temperature plants , may deposit thicker layers of wax on thier leaves , in very windy conditions . They may have vascyal tissues which is more ligngified . Plants hsow speicifc repsosnes to the threa herbivores , employign the follwoing chemical defecnes .
what is tropisms
they are directionl growth resposnes of plants
what is phototropism
shooots grow toward light (they are positively phototrophic ) , which enables them to photosynttheise .
what is geotropisms
roots grow towards the pull of gravity . This anchors them int he soil and helps them to take up water , which is needed for suport ( to keep cells turgid ) , as a raw material for photosyntehsis and ot help coo t he plant . There willa lso be minerals , sucha s nitate int he water needed for the synthesis of amino aicds .
what is chemotropisms
on a lower , pollen tube , growss down the sytle attracted byc hemicals , towards the ovary where feritlisaiton can take place .
what is thigmotropisms
shoots of climbind plants , such as ivy ,w ind aroudn other plants or solid strucutres to gain supports .
-If a plant , responds , towards a stimulus , it is a positive topic resposne , If a plbt repsonds away foma stimulus , it is a positive tropic repsosne . If a palnt respodns aey froma stimulus , it is stilla tropi cresposne , but negative rather than positive .
non-directional resposnes
non directionla reposnses to external stimulia re called nastic resposnes . The sensitive plant , mimosa pudica ,r epsonds tot ouch wiht a duden folding of the elaves , this response is an example of THIGMONASTY
effect of the hormone cytokinins
promoote cell division ,
-delay leaf senescence
-pvercpme apical dominance
promote celle xpansion
absicic acid
inibibts , seeds germinaiton ,a dn grwoth ,
-causes stomatal closure n , when the plant is stressed b low water availiabitli .
what are auxins
promote , cell elongation ,
inhibit gorth of side shoots
ihibit leaf absicions .
what are gibberelins
promoe , seed germination , and growth of stems
what are ethene
promote fruit ripenigng
how do hormones move aounr the body
active transport
diffusion
mass flow int he phloem sap or xylen vessel
contorl of resposnes - the role of plant hormones
hormones coordinate plant resposnes to enviornemnta stimuli . Like animal plant hormones , plant hormones are chemical messnegers that cn be tranpsorted away from thier site of manufacture to act on other sities of p the plant , like target cells or tissues .
-They sare not produced in endocirne gland bt by cels in a variety of tissues in the plant .
control of resposnes - the role of plant hormones (2)
when hormones reach thier targetc ells ,t hey bind to recepotrs on the pllasma memrbane . speicifc hormones , habe speciifc shapes which can only bind to speicifc receptors with complementary shapes on the membranes of particualr cells .
contro of repsosnes (3)
the specifric bindig amkes sure that hte hormones only act upon the correct tissues . Such hormones can have different effects on different tissues , some can apmlif eachoters efects , and some can , even cnacel out each others effecrs . Hormones cna infleunce cell diviison , cell elongation and cell differnetaiton .
What is apical dominance
inhibition of lateral buds , further down the shhot , by chemicals produced by the apical bud at the tip , of a plant shoot .
what are auxins
plant hormones , they are respoosible for promoting plant growht .
what are gibberelins
plant hormones which are reposinbile for contorl of stem elongation and seed germinaiton .
what are auxins -
what happens if you break the shoot tip the apex of plant
-plant hormones which are responsible for regulaitng plant growth .
-the plant starts to grow , side branches , from lateral buds , that were previously dormant .
what do researchers suggest that auxins from the apical buds prevent
they prevent lateral buds formg rowing . Whent he tip is rmoved ,a uxin elvels int he shoot drop and the buds gro .
how did scienitts test ther hypotehsis for auxins howevr ewhat was a porblem
scientsits applied a paste containing aucins to the cut end of the shoot and tip is removved , auxin levels in the shoot dorp and the buds grow .
-However , scienits manpualtion of the plant , could have an unexpected effect , upon exposure , to ocxygenc ells o the cut end of the stem could have porduced a hormone , tat promoted alteral bud growth .
-BECAUSE OF THIS , scienitntis applied a ring of auxin transport inhibitor below the apex of the shoot , the lateral buds grew .
auxin research results
suggested that normal levels , of auxin evels in the lateral buds inibit growth wherby low auxin lrevels , promtoe growth .
-However ,t he two variables in auxin levels an dgrowht ihibiton may habe no effect on eachother , but could both be aggected bya third varibae .
what was the third varibale in the auxin research that caused a change
it dosne specify , but year alter , different scnients remakred auin level sin aleral buds of kidney bean actually icnreases , when shoot tip as cut off . Scienits believe other tqo hormeos are involeed
first hormone that researchers think are invovled
absicic cid , inihidbits bud gorwth - high ucin in th shhot my keep absisic acid , levle shigh in bd , when the ti (the osure of auscin ) is removed basiidc acid levels drop and the bud starts to grow .
xsecond hormone cienits belive help promtoe bud growth
directly applying cytokokinins , to buds can overrid ehte plical dominnce effect . High levle sof auxin amke the hsoot paex a isnkf or cyokinis produced int he rooots most . of the cyotkin goes to the shot pex , when the apex is removed cyotkinsi spreads evenlyaround the plant .
japanese sutdy part one
scientists tested gibberellic acid on many different plants . When they a pplied it to dwarf varitieis , plants such as maize and peas or to a roseete plants they grew taller .
-This suggetss tht igberellic acid is reposnible for plant stem growth . hwoeber , thinka bott hte experiment acc investigated a natrual phenoemenon , just because ga3 ,c an cuase stem elongation . it does not mena it foes so in ntur .
in Japan - stem elongation
in jspsn , a fungus ,c auses a disease which amkes rice grow very tall , , hr fungsl vompoufnd inboblrf str ibbrtlind sn giberellic icd GA4 .
japanese study part three
this does not mean it does so in anture . An experiment like this needs tto work within conentraitons of gibberelins nturally found in palnts , and in prts of the plant that gibberlin m oelcules normally reach .
japanese stud part four
researchers foudn a way to meet the criteria , they compred ga levels another memeber of the gibberelin family of tall plea palnts , homozygous for the doinant le allele and dwrd pea plants , homozygous for the recessive le allele ,w hich were otherwise genetically idneitcal , they found th tplants with HIGHER GA 1 levels were tallers .
japenes study part five
however , to show that ga1 , direcly causes stem growth , researchers need to know how ga 1 is formed . They wormed out tht hte le gene , was responsible for producing the enzyme that converted ga20 to ga1 .
japennes sutdy part six
then the researchers chose a pea plant with mutation tht bloacks gibberelin rpoducion between ent karuee and ga12 aldehyde , in th pathaay shown if fure 3 , thos eplans produce no giberlin nd grow ot onlyabout oen cm tall . The researchers GRAFTED (like transplanting ) , shoot onto a hozmohyous le palnt , which cannot convert ga20 to ga1 ,and it gree taller .
jpaenes sutdy part seven
such shhot ,w ith no ga 30 , of its own does have the enzyme to convert GA20 to GA1 , and it can use the unesed ga20 , form th enormal plant , because the shoot gorw tall this confimed ga 1 cwas the tehc ause of elongation .
jaPANES SUTDY PART seven yayy
further studies habe shown that gibberelins cause gorwth in the itnenrodes bys timualitn cell elongtion (by loosening cel walls _ and cell divisoin (by stimualting porduction of a portein that contorls the cell cycle ) .
Seed germination
gibberellins also promot e seed germinaiton . When the seed absorbs water the embryo releases gibbereli which travels to the alerone laer int he dnosperm region of the seeds . the gibberlins enbale ht epriciton of amalse , which can break downs tarhc into glcose t his provides a usbsrae of resiaiton fo the mryso it foes ,g lcos ealso needed for portein shytnehsis .
where does plant cell growth occur
in plants , the cell wall limits the cells ability to divide and expand , growth only happens , in particualr places , in the plan where there are groups of immarute cells ae sill cpable of dividng clled meristems .
what are apical merisrme
apical meristems are at the tips of apices . of roots and shoots and are reposnsibel for the roots and shoots getitng lonegr .
where are lateral bud meristems
theya re found in the buds , these cn give rise to side shhots
where are lateral meristems
lateral meristems forming a cclinder nea the outside of roots and shows are reposinbiel for roots nd shoots getitng iewder
In soe plants intercalry meristems are located between the ndoes ,w here the leaces and buds branch off the stem . GROWTH beteen the dones is rposnibel for the shot getting logner .
investigating phototropics
repsosnes cna be investige using epiements . The expermient have an experimental palnt and a contol plnt , contorl is iluminted alls ied
experiemntal has illumiantion form sut one side
seberla days the shot bends towards light , AS THE SHADYS IDE OF TSHOOT is elonage dmore than illumined isde .
mean and standard eciaiotn of lengths has increased on shady side
investiating geotropic repsosnes
a contorl plant is constnaly spun (very slwoly ) by a machine claled kilinostt ,e nsuirng graivity appleid eually on alls ide
for contor
cfor pxerntal plant , kilnostat is not switched on grvaity oly applied to one side
expriemnl , root bends downwnards , becau eupeprside hs elonaged more thn lower side , shhot beens upwarda s lwoer side of shhot of shoot enloaed more than upper side . in cntorl palnt , noth root and shoto grow horiziontall .
shoot tip is placed on agar block , chemica laer idenitifed as auxin ,d iffuse from shoot tip ito agrar
control
agar block containign auxin stimulte growth
SHOOT TIP I PACED On an agrar block ,c hemical alter idenitifed as auxin diffuses form shoot tip into ara
OFFSET BLOCK contianig auxin ostjmulted cured growht
BLOCKS CONTIANIG NO AXUN HAE NO EFFECT .
WHY DOES shining liht one one side cuase
causes axuins ot be tranported gto shaded side causin cells there to eonae mor uicly making th shoot bend towards light , .
mechanisms of auxin effect
auxin icnreases the stretchiness of the cell wall by pormoting the active transport of H+ , by n ATPase enzyme ont he plsma membrane into the cell wall . The reulitng low pH provide doptimum conditions ofr wll loosenng enxme expansisns to wotk . These enzmes break ondws within the celllose , icnrese hyorgen ions also didrupt hydrgogen bodns so walls become less ridig and can ecxpnd nd cels take in wate r.
how does auxin cause geotropic repsosnes inr oots
auxin is aso invovled in georopic reposnes of roots in a root lying lat ,w ent disvoered that auxin accumalted on the lwoer side , where it inhibts celle lngaiton the upper sid cuaw celel elongaion on lwoer sde makin shohts lign fla ebd upwds . THIS HAPPENS BCAUSE ROOT AND SHOTO CELLS IN TH ELONAGTION ZONE EXHIBIT DIFFEENT RESOSNES TO THE SAME CONC OF AUXINS . check figrue 7 on page 87 .
why can artifical auxins be used
to prevent leaf snd fruit drop and to promote flowering for commercial flower prduction n high cocnentraitons auxinx can also promtoe fuir tdrop . This is usueful if there are too manys mall furit tht iwll be difficult ot sell the palnt poduces fewer large fuit . other uses of auxins ae shown . in tbale .
first commerical use of auxins
taking cuttings - dippign in the end of a cutting in rooting powder , before planting it , enocurgaes root growth ,a s rooting powder cotians auxins and talcum powder .
second commercial sue of auxins - seedless fruit
treting unpollinted flowers with auxin cn promote growth of seedless fruit , pplyign auxin promtoes ovule grwoth ,w hich trigger automatic porducito of auxin by tissue sint he developign furit helpign to compete the devleopemntl process .
thrid comemrcial use of auxins 0 herbicides
auxins are used a shebricides o killw eeds . because hey are man amde palnts iwll fidn htem moe didfficul to rbeak down a,nd they can aciwthin the paln fo lonegr . THey promote shoot grwoth much ft stem cnnot usport isefl bucked and ies .
cytokinins
cytokoinindd cn delylef enscene they cn be used to preent yeloing of elttuc eleaves atet they have been piced .
cytokingin are used to prevent yellwoing of lettuc eleves after they have ene piced .
-cytokonia re used in tissue culture to help mas prouce plans , cytokoni promote bud and shot growth from small peices of tissue taken from a parent palnt .
- ths prduces a short anser shoot , wth a lot of side branche s, which cna be can be split into ltos of smal palnts ,e ahc of thes eis then grown sperelt .
gibberelins for fruit production (1)
gibberellins delay senescne in citrus fruit ,e xtenidng the time furits can be left npicked making the availbel for logner in the shops .
gibberellins for fruit production (2)
gibberelins acting with cytokinis can make apples elonagte to improve thier shape
gibberellins for fruit production (3)
without gibberlins buch of grapes are very compct , this restricts the growth of idnivuda grapes , with gibberleins the grape stlk elnagte theya re less compact nd the grapes get biger .
brewing -
barely seeds germinate ,t he aleurone alyer of the see dporduces amyalsw enzmes tht break down stored strarch into maltose .
-usually , the genes fo rmayals eproduitn are switched on by nturlaly ocrring igberlins , adding giberlin can speed up the proces , mal tis then produced yd ring and grinding up the seeds .
being a plant breeder
a plant breeders job is to produe palnt with desired charaterisitcs , so by bredinc together other plant suusally tak emany egenraitons
conifer palnts take even lonegr , so gibberlins speed up the procss by indivcing seed ormaiton on yougn trees , SEED ocmpnies that harvest seds form beinnial palnts , can add ibberellins to idncue seed produciton .
why is stopping plants making gibberelins also sueful
sorayign , with gibberleins ytnehsis infhibtos can keep flwoer short nd stokcy , and ensure tht thr intenoed of corp palnts sty short , helpign to prevent lodging
when can lodging occur
lodging occurs inw e summers ,s tem bends over becaus eof weight of water collecte dirpened seeds makign corp didfuclt ot havest .
commercial use of ethene (1)
speeidng up fruit riepening ina pples tomaotes and cirturs furits
commercial sues of ethene (2)
promoting , furit drop in cootn , cheryr and walnut .
commerical uses of ethene (e3)
prpomoting i female sex epression in cucumebrs reducing the chane of slef-pollianiton and icnreasing iel d
commercial sues of ethene (4)
promtoign altel growht in some palnts yiedling compact floweirng tems .
restrcitng effects of ethene
storing ethenes effects can also e sueufl sotrin furit t a low tempw ith little ocygena d highc aborndioxide vels , prevents eheten syntheis and furit riepnign. mean fruits oted of rlonger essneitla hn hsipping unripe banans ,
