Sisitimu Yekubereka Mumiti Inotumbuka
Zvirimwa zvinotumbuka, kana kuti maangiosperms, ndiwo mapoka akasiyana-siyana ezvirimwa pasi pano. Kupararira kwazvo munzvimbo dzakasiyana-siyana kunokonzerwa zvikuru nemaitiro azvo ekubereka anoshanda uye anochinjika. Muzvirimwa zvinotumbuka, kubereka kunoitika zvikuru kuburikidza nemaruva, nhengo dzekubereka dzinobvumira kuburitsa mhodzi, kubereka, kuumba mbeu, uye kukura kwemichero. Chinyorwa chino chinotaura nezvemaumbirwo emaruva, maitiro ekubereka, uye kusiyana kwakasiyana-siyana mumaitiro ekubereka muzvirimwa zvinotumbuka.
1. Maruva senzira yekubereka
Maruva akagadziriswa magadzirirwo emashizha nemidzi akagadzirirwa kubereka. Kazhinji, maruva anoumbwa nezvikamu zvikuru zvakati wandei:
1. Maruva emaruva (sepals)
Kazhinji kacho ruvara rwacho rwegirini uye runobatsira kuchengetedza ruva richiri pfundo.
2. Korona yeruva (petal)
Kazhinji dzine mavara akajeka uye dzinoshanda pakukwezva zvinokura mbeu zvakaita sezvipembenene, shiri, kana zviremwaremwa.
3. Stamen - nhengo yekubereka yemurume
Zvinosanganisira:
- Filamenti
– Anther, uko mukume unoumbwa.
4. Pistil (carpel) - nhengo yekubereka yemukadzi
Zvinosanganisira:
– Kusarura: nzvimbo inonamira mukume.
– Maitiro: nzira inoenda ku ovary.
– Mazai (mazai): panowanikwa mbeu (mazai).
Haasi maruva ese ane chimiro chakakwana. Kune maruva akakwana (ane stamens ne pistils) uye maruva asina kukwana (ane maruva echirume chete kana echikadzi chete). Uyezve, kune zvirimwa zve monoecious (zvine maruva echirume neechikadzi pamunhu mumwe chete, senge chibage) uye zvirimwa zve dioecious (zvine maruva echirume neechikadzi pamunhu mumwe chete, senge muchero wenyoka).
2. Kuumbwa kweMasero Ebonde muMiti Inotumbuka
Kubereka vana mu angiosperms kunosanganisira kuumbwa kwema gametes echirume neechikadzi kuburikidza nemaitiro ekupatsanurana akakosha.
a. Kuumbwa kweMarume Gametes (Mhuka/Mhuka)
Tsanga dzemukume dzinoumbwa muanther. Mukati meanther, mune masero e microspore anozopinda mu meiosis kuti agadzire haploid microspores. Ma microspores acho anozokura kuita tsanga dzemukume dzine:
– Masero emiti (anozogadzira machubhu ekubereka)
– Masero anogadzira mbeu (anopatsanura kuita mbeu mbiri)
Saka, mukume unova "mutakuri" wemasero embeu kuenda kuovheni.
b. Kuumbwa kweMatumbu echikadzi (Embryonic Sacs)
Masero echikadzi anoumbwa mukati memazai ari mumazai. Sero remai remegaspore rinoitwa meiosis kuti rigadzire mamegaspores mana, asi kazhinji rimwe chete ndiro rinorarama rozokura mu embryo sac. Embryo sac ine masero akakosha akati wandei:
– Masero ezai (zai)
– Manuclei maviri epolar
- Masero eSynergid (anobatsira pakubereka)
– Masero ekudzivirira chirwere (anowanzoita basa guru mukudya)
Chimiro ichi chichava nzvimbo inoberekeswa mbeu.
3. Kubereka
Kubereka mbeu inzira yekufambisa mukume kubva kuanther kuenda kuchirwere chestigma. Kubereka mbeu idanho guru nekuti ndiyo nzira yekuenda kumbeu. Kubereka mbeu kunogona kuitika nenzira dzakasiyana-siyana:
1. Anemogamy (nemhepo)
Mienzaniso: mupunga, chibage, huswa. Maruva anowanzova madiki, asingaonekwe, uye anogadzira mukume wakawanda, wakareruka.
2. Matumbu (nezvipembenene)
Mienzaniso: marinara ezuva, jasmine. Makororo avo anoyevedza, anowanzo buritsa nectar uye kunhuhwirira.
3. Ornithogamy (neshiri)
Mienzaniso: hibiscus mune dzimwe nzvimbo, kana zvirimwa zvine maruva matsvuku uye ane nectar yakawanda.
4. Chiropterogamy (nezviremwaremwa)
Mienzaniso: durian nedzimwe cacti. Maruva adzo anowanzo maruva husiku uye ane hwema hwakasimba.
5. Hydrogamy (nemvura)
Inowanikwa mune zvimwe zvinomera zvemumvura.
Zvichienderana nekwakabva mukume, kuberekesa mukume kwakakamurwa kuita:
- Autogamy: kuzviberekesa (kuberekana kwemukume ku pistil muruva rimwe chete)
- Geitonogamy: pakati pemaruva pamunhu mumwe chete
– Allogamy/Xenogamy: pakati pevanhu vakasiyana (kunowedzera kusiyana kwemajini)
4. Kuberekesa Kaviri: Hunhu Hwakajairika hweAngiosperms
Mushure mekunge tsanga dzemukume dzanamatira kune stigma, dzinomera dzogadzira chubhu yemukume inokura kuburikidza nenzira inoenda kuovule. Sero rinobereka rinopatsanuka kuti rigadzire masero maviri embeu. Kana chubhu yasvika mu embryo sac, chiitiko che angiosperm, double fertilization, chinoitika:
1. Mbeu yekutanga inosanganisa zai → ichigadzira zygote (2n) iyo inozokura kuita mwana ari mudumbu.
2. Mbeu yechipiri inoberekesa manyuchi maviri epolar → ichigadzira endosperm (3n) senzvimbo yekuchengetedza chikafu chemwana ari mudumbu.
Kuberekesa kaviri uku kwakakosha zvikuru nekuti endosperm inongoumbwa chete kana paine kuberekesa, kuitira kuti simba remwana ari mudumbu riwanikwe zvakanaka.
5. Kuumbwa kweMbeu neMichero
Mushure mekusangana kwembeu:
– Mazai anokura kuita mbeu
- Ovary inokura kuita muchero
a. Mbeu
Mbeu dzinowanzo sanganisira:
– Embryo (chirimwa chitsva chinodiwa)
– Endosperm (chikafu chinochengetwa, mumhando dzakasiyana-siyana)
– Goko rembeu (testa) sedziviriro
Maumbirwo embeu anobvumira chirimwa kurarama mumamiriro ezvinhu asina kunaka (semuenzaniso akaoma kana kutonhora) uye kupararira kure nechirimwa chikuru.
b. Muchero
Michero inodzivirira mbeu uye inobatsira mukupararira kwembeu. Mimwe michero ine nyama yakawanda, inokwezva mhuka dzinodya michero (semuenzaniso mango), nepo mimwe yakaoma, inoparadzirwa nyore nyore nemhepo (semuenzaniso donje nedandelions). Kupararira kwembeu kunogona kuitika nemhepo, mvura, mhuka, kana autochory.
6. Kumera uye Kukura kweVanhu Vatsva
Kana mamiriro ekunze akanaka (mvura yakakwana, tembiricha yakakodzera, uye kuwanikwa kweokisijeni), mbeu inomera. Mwana ari mudumbu anokura kuita seedling nekushandisa zvinovaka muviri zviri mu endosperm kana cotyledon. Mushure mekukura mashizha nemidzi zvinoshanda, chirimwa chidiki chinokwanisa photosynthesis uye chinokura kuita chikuru, pakupedzisira chichibereka maruva zvakare.
7. Kusiyana uye Kugadziriswa kweSistimu Yekubereka
Zvirimwa zvinotumbuka zvine nzira dzakasiyana-siyana dzekuwedzera kubudirira kwekubereka, dzakadai se:
– Heterostyly: musiyano pakureba kwepistil ne stamens kudzivirira kuzviberekesa.
– Dichogamy: nguva yekukura kwema stamens nema pistils haina kufanana.
– Apomixis: kuumbwa kwembeu pasina kuberekesa (mune zvimwe zvirimwa), zvichibvumira kuberekana nekukurumidza zvine hunhu hwakafanana hwemajini.
– Kushanduka-shanduka pamwe chete nezvinoyamura maruva: chimiro cheruva, ruvara, uye hwema zvinoenderana nezvinodiwa nevamwe vanoyamura maruva kuti zviwedzere kushanda zvakanaka kwezvinoyamura maruva.
Penutup
Sisitimu yekubereka yezvirimwa zvinotumbuka inzira dzakarongwa zvakanaka, kubva pakuumbwa kwegamete, kuberekesa mbeu, kuberekesa mbeu mbiri, kusvika pakuumbwa kwembeu nemichero. Chinhu chikuru chinoita kuti maruva embeu abereke zvakanaka ndechekuti maruva acho ave nhengo dzinoshanda dzekubereka, pamwe nekuberekesa mbeu mbiri, izvo zvinoita kuti mwana awane chikafu. Kusiyana-siyana kwenzira dzekuberekesa mbeu uye kuchinja kwemhando yekubereka kunoita kuti zvirimwa zvinotumbuka zvirarame uye zvikure zvakanaka mune chero ecosystem. Kunzwisisa sisitimu iyi hakungokoshi pakudzidza biology chete asiwo kunobatsira mukurima, kubereka zvirimwa, uye kuchengetedza zvipenyu zvakasiyana-siyana.
