Ngenxa yendalo yethu, kulula ngathi ukuba nomfanekiso-ngqondweni wendlela izilwanyana ezizala ngayo, ekubeni inkqubo yazo yokuzala idla ngokufana neyethu. Nangona kunjalo, kuthatha ixesha elide ukufumana ezo zinto zifana nehlabathi lezityalo. Bakwenza njani oko? Yintoni ukuchumisa kwezityalo?
Injongo yeli nqaku kukucacisa ukuba yintoni na ukuchumisa izityalo. Kule nto siza kuthetha ngamaqela amabini amakhulu akhoyo: I-Angiosperms kunye ne-gymnosperms. Ngoko ke musa ukuthandabuza ukuqhubeka ufunda ukuba unomdla kulo mbandela kwaye ufuna ukwazi ngakumbi malunga nokuchumisa kwezityalo.
Ukuchunyiswa kwezityalo
Phambi kokuba sicacise ukuchumisa kwezityalo, siza kuqala sigqabaze ngokuba yintoni ingcamango yokuchumisa. Yinkqubo ekwenziwa ngayo oko Iigametes ezimbini, inkunzi nemazi, zixubana ngexesha lokuzala. Ngale ndlela, i-zygote idalwe equlethe i-genome, imveliso yabazali.
Kwihlabathi lezityalo, Umvumvuzelwano lwenziwa kuqala. Amagqabi enzala ayindoda enza iinkozo ze-pollen ezithwalwa zizinambuzane okanye ngumoya ukuya kwibala. Kulapho zintshula khona. Xa sithetha ngezityalo, asidli ngokubhekisa kwi-gametes, kodwa kwiimbewu. Ukhozo ngalunye lomungu ludla ngokuba neeseli ezimbini zokuzala, okanye iigametes. Nangona kunjalo, kukho iindlela ezahlukeneyo ezisetyenziswa zizityalo, kuba ingezizo zonke iintlobo ezifanayo, enyanisweni zahluke kakhulu xa kufikwa ekuveliseni.
Njengoko usazi, izityalo zinokwahlulwa ngeendlela ezininzi. Kukho inani elikhulu lamaqela, iiklasi kunye neentlobo zemifuno kunye neentlobo zezilwanyana ezininzi. Noko ke, kukho amaqela amabini amakhulu awahlukeneyo ngendlela azalana ngayo. Lo nto, Kukho imifuno eneentyantyambo kunye nalabo abangenazo iintyatyambo. Ezokuqala zaziwa ngokuba zii-angiosperms kwaye zezona zityalo zininzi kule planethi. Ukongeza, kwezi ntlobo zimbini zemifuno zezona zamva nje. Ngakolunye uhlangothi, izityalo ezingenazo iintyatyambo ziyinxalenye yeqela le imithambo. Ezi yayizezokuqala ukuvela emhlabeni, nangaphambi kokuba iidinosaur.
Phakathi kwe-angiosperms zizityalo ezahlukeneyo ezifana nezihlahla, imithi, azaleas, i-dimorphothecae, njl. Ngokubhekiselele kwi-gymnosperms, ezi ziqulunqwe kakhulu amakhonkco. Eminye imizekelo yeli qela iya kuba yimisedare, yews, ipayini. I-Cycads ikwazezi zityalo ze-gymnosperm. Kodwa ungakhathazeki, siza kuthetha banzi malunga neentlobo zombini zezityalo, izakhiwo zazo kunye nendlela okwenzeka ngayo ukuchumisa.
IiGymnosperms
Masiqale ngee-gymnosperms. Nangona kuyinyani ukuba ezi zityalo zaziwa ngokungabi nantyatyambo, zinjalo, kodwa hayi ezo ziqhelekileyo esizicingelayo. Iintyatyambo zayo azinayo i-sepals okanye iipetals, kodwa ezi zibhinqa zenza uhlobo lwe-cone eluhlaza kunye nohlaza oluphela lube ziziqhamo zobuxoki, njenge-pine cones.
Izityalo zeli qela zineentyatyambo ezizinkunzi nezemazi. Le yokugqibela inesikali, ii-ovules ezimbini kunye nebract eyenza ikhowuni yemazi ngokuhlanganisana kufutshane neasi yeentyatyambo. I-ovule nganye ine-embryo sac ene-archegonia ezimbini ngaphakathi kuyo. ezithi, nazo, zibe neegametes ezimbini zabasetyhini okanye ii-oospheres nganye. Masiyicacise le migaqo:
- IArchegonia: Lilungu lobufazi lokuzala. amakhowa, ulwelwe y iibryophytes, ezifana ne-mosses kunye nezinye izityalo ze-vascular ezifana ne-ferns. Incediswa lilungu lobudoda elibizwa ngokuba yi-antheridium.
- Oospheres: Yigamete emazi yezityalo. Bavela kwinto ebizwa ngokuba yi-megaspore ngenkqubo ebizwa ngokuba yi-megagametogenesis. Kwinqanaba elisisiseko sinokuthi oku kubandakanya ulwahlulo lwemitotic. Ngexesha lokuchumisa kabini, i-oospheres idibana ne-nuclei yemveliso evela kwinkozo ye-pollen kwaye ngaloo ndlela ivelisa i-embryo.
Ngokuphathelele iintyatyambo zobuduna, ezi zenza iicones eziziinkunzi ezijikeleze iasi yeentyatyambo. Baye isikali kwaye kwakhona microsporangia ezimbini okanye i-pollen sacs apho ziphela zenza iiseli zomama ezithi zivelise iinkozo ze-pollen ezidumileyo. Ngaphakathi kuzo kukho iigametes ezimbini zamadoda, ezikwabizwa ngokuba zii-anterozoids. Zikwaqulathe iingxowa zomoya ezimbini ezinceda ukusasaza de zifike kwintyatyambo yobumazi. Kule meko ndicinga ukuba kuya kuba kuhle ukuchaza ezinye iikhonsepthi:
- I-Microsporangia: Zizakhiwo ezivelisayo kwaye zikwaqulethe iimbewu. Le yimizimba emincinci enenjongo yokusasazeka kwaye iphile ixesha elide.
- IiAntherozoids: Ngokusisiseko yinkunzi yegamete, elingana nedlozi lethu.
Ukuchunyiswa kwezityalo ze-gymnosperm
Ukwazi okuncinci malunga nezakhiwo zeentyantyambo zesilisa kunye nesetyhini ze-gymnosperms, ngoku siza kuphawula malunga nendlela oku kuchumisa kusebenza ngayo. Kufuneka kuqatshelwe ukuba i-pollen grain inokuthatha unyaka ukuntshula, xa intyatyambo yemazi ifikeleleke. Xa oku kusenzeka, ityhubhu ye-pollen ivuleka ngokucothayo kwinto ebizwa ngokuba yi-nucellus ye-ovule. Xa ifikelela kwi-gametophyte yabasetyhini, umsebenzi wayo olandelayo kukunqumla intamo ye-archegonium uze ungene kwi-oosphere. apho ukhuphela khona wonke umxholo wakho. Kungelo xesha apho ukuchunyiswa kwezityalo ze-gymnosperm kwenzeka.
Ngexesha lale nkqubo, enye yeegametes iphelela ekudibaneni nenucleus yaloo oosphere eyenzeka kuyo. Ngenxa yoko, i-zygote yenziwa, eyiseli apho i-embryo yenziwa kwaye iphuhlise. Ngokuphathelele i-nucleus yezityalo, ezinye iiseli ze-archegonium kunye nenye i-gamete eyindoda, zonke ziyancipha. Okwangoku, i-endosperm, eyenziwe ngeeseli ezigciniweyo, ijikeleze i-embryo, ekhuselwe yi- integument ye-ovule, ethi yona ikhanye. I-embryo ithathwa njengevuthwe ngokupheleleyo xa imbewu ikhululiwe. Le nkqubo inokuthatha ngokulula iminyaka emibini ukusuka ekuveleni kweentyatyambo.
Kwimeko yembewu evela kwipineyini, isambatho sembewu yi-diploid kwaye iveliswa yi-sporophyte yomama. Ngokumalunga ne-endosperm yokuqala okanye izicubu ezigciniweyo, le yi-haploid kuba iyinxalenye ye-gametophyte yabasetyhini. Emva kokukhulelwa, i-embryo ye-diploid yenziwa, eyi-sporophyte entsha.
IiAngiosperms
Sele sisazi ukuba zeziphi ii-gymnosperms kunye nendlela ezisebenza ngayo, kodwa kuthekani nge-angiosperms? Ngaphambi kokuchaza ukuchumisa kwezi zityalo, Okokuqala kufuneka sicacise ezinye iikhonsepthi Ukuqonda ngcono inkqubo:
- IiCarpels: Lawa ngamagqabi aguquliweyo athi, xa ewonke, enze inxalenye yokuzala yabasetyhini kwintyatyambo yezityalo ze-angiosperm. Iseti yazo zonke iikhapeli zentyatyambo ibizwa ngokuba yigynoecium.
- Ibala: Yilaa nxalenye ye-gynoecium efumana umungu xa kusenziwa ipoleni.
- I-Micropyle: Ikwabizwa ngokuba yi-micropyle, ngumngxuma okanye intunja efunyenwe kwindawo ye-apical ye-seminal rudiments okanye ii-ovules.
- Synergists: Ziiseli ezinenucleus efumaneka ekupheleni kwe-embryo sac yezityalo ze-angiosperm. Ingxowa ye-embryo nganye inezimbini zazo. Ii-synergids zimbini kunye zenza izixhobo zefiliform okanye izixhobo zefilar. Kufuneka kuqatshelwe ukuba bancedisa i-oosphere ngexesha lenkqubo yokuchumisa.
- iinuclei zepolar: Ezi nuclei ziiseli ezifumaneka ngaphakathi kwe-embryo sac, i-gametophyte yabasetyhini okanye i-ovary. Bangenelela ekuchumiseni imifuno.
Kufuneka kuthiwe i-embryo sac nganye ineentlobo ezahlukeneyo zeeseli, zazo ezichumileyo ziinuclei zepolar kunye ne-ovule. Nangona kunjalo, ezo zinyumba, ezinokuthi zibe yi-antipodal kunye ne-synergistic, nazo ziyasebenzisana ngexesha lenkqubo yokuchumisa.
ukuchunyiswa kwezityalo ze-angiosperm
Ukugqiba ngomxholo wokuchumisa kwizityalo, siza kuthetha malunga nokusebenza kwe-angiosperms. Nje ukuba i-pollination ye-carpel yenzekile, ulwelo oluneswekile, oluqulunqwe ikakhulu yi-sucrose kwaye luveliswe yi-stigma ekhulileyo, ivuselela ukuntshula kwembewu yomungu. Kukhozo ngalunye kwezi kukho ityhubhu ye-pollen evelayo injongo yayo kukudala indlela ngokusebenzisa isimbo de ifike kwi-gametophyte yabasetyhini okanye i-embryo sac yezityalo ze-angiosperm. Esi singxobo se-embryo singaphakathi kwi-ovule.
Iigetethi zamadoda okanye i-nuclei ezalanayo ihamba ngetyhubhu ye-pollen de ifike kwi-micropyle. I-tube ye-pollen idlula kwesi sakhiwo kwaye ikhupha zonke izinto zayo kwi-embryo sac, kufutshane nenye yee-synergids ezimbini. Emva kwale nkqubo, i-nuclei yokuvelisa idibanisa zombini i-oosphere kunye ne-polar nuclei, yiyo loo nto ibizwa ngokuba "i-double fertilization".
Kukho iinkozo ezininzi ze-pollen ezihlala zifikelela kwibala kwaye, ngenxa yoko, zihluma. Nangona kunjalo, inye kuphela kuzo eya kuvelisa ukuchumisa. Emva kokuba i-ovary ikhuliswe, iqala ukukhula ibe sisiqhamo. Kwezo ziqhamo zineqela imbewu, kukho iinkozo ezininzi ze-pollen eziyimfuneko ukuze zidibanise kunye ne-ovules nganye.
Iyahlekisa indlela indalo elungiselele ngayo yonke into ukuze iintlobo ezahlukeneyo zemifuno zikwazi ukuzala, akunjalo? Ngaphandle kwamathandabuzo, lo mhlaba uzaliswe yindalo emangalisayo kunye nobuchule bokuzala.