Gymnosperms

Gymnosperms umkhondo imbali yabo ukususela kwixesha paleofita. Kungenxa kwimbali yamandulo zesityalo iphawulwa baziphatha ibihlungu. Baba abameli eziyintloko izihluma. Ngasekupheleni flora ixesha Permian kuzisa utshintsho ezinkulu: ukubuyisela ixesha imigxobhozo amalahle kunye kwizityalo zabo kufika ixesha ngokupheleleyo izityalo ezahlukeneyo. Gymnosperms ingakumbi ichuma yaye zikwizikhundla eziphambili kweli xesha le Mesozoic.

Ukuvela eli qela izityalo yaba linyathelo eliya phambili kwinkqubo yendaleko. UFern eyayivele kwi inkqubo ukuzalela medium zolwelo iyafuneka. Ingxabano, ukufumana ngaphandle sporangium kumhlaba ofumileyo, intshula prothallia kunye esini. Ukuba isityalo kuphuhliso zeemo ezahlukeneyo imbewu, inxenye yabo nokuphuhlisa prothallia ezimbini: ababhinqileyo elinye kunye nezinye kunye amalungu eyindoda. Ngaphezu koko, inkqubo ifakwe lifika, archegonium - cell sex female - ukuba connect with inkunzi iseli ngesondo, kule meko kukho imfuneko ukufumaneka kwamanzi. Bobu ngxoxo kukuba ezi kumila pre-ezikhoyo psilophytes bavela izityalo nezilwanyana zasemanzini. Olu phawu efanayo ukuhanjiswa yezityalo kulinganiselwe kakhulu - uhlaza ukuba kwenzeka kuphela kwiindawo nokufuma eziphakamileyo.

Iqela elitsha kuyalahleka uxhomekeko lobukho nokungabikho kwamanzi. A lokwanda gymnosperms kwezityalo yile ilandelayo: umoya ethwele umungu nembewu nophuhliso esiya kwi ekunene ikopi koomama. Kodwa oku uncedo kuphela kweli qela. Ukuba yengxabano 1 iseli kuphela, nto leyo ubonelelo eliqingqiweyo izondlo, yophela nayo ke imbewu yemfundo sele multicellular, yayiqinisekisa nokubonelelwa kwezinto ezibalulekileyo ngexesha kuphuhliso osandul. Ngaphezu koko, ubukho esikalini kuba umbungu imbewu iyakhusela yendalo oluthembekileyo oluvela kwiingozi zokusingqongileyo. Ezi mpawu ezintsha lobume ziye kubalulekile ukuba nasekusungulweni kwale nezihluma; gymnosperms ukufumana iimeko ephuculweyo ukuzala nolondolozo.

Namhlanje ezi zityalo Izazi neliqaqambileyo kwiklasi eyahlukileyo. Yonke imbali zophuhliso kwabo kubonakala ukuba kwenzeka angiosperms ezivela gymnosperms. Onke amalungu eli qela (gymnosperms) yahlulwe yangamacandelo amane: ginkgovidnye, gnetophyta, cycad, Conifers.

Yintoni ohlanganisa eli qela? Ziintoni iimpawu gymnosperms? Bonke bephela imithana okanye imithi, lomthobo ubungakanani obukhulu. Abanye, silnovetvyaschiesya, azakubalulwa inani elikhulu amagqabi ezincinane (inokuba enamaxolo). Abanye, Noko ke, branched kancinane, kodwa amagqabi enkulu feathery. Xylem ngaphandle ezityeni, kunye neqabane phloem cell-free - enye imfanelo eqhelekileyo gymnosperms kakhulu. They are heterosporous. Imilo, ubungakanani kunye nolwakhiwo lwe ngemithamo kwaye makrosporofill ezahlukeneyo kakhulu. ukukhula mahala kwi yokubaleka eqhelekileyo - ukusuka omfisi imbewu abangekaphuhli kwi strobilae (amahlumelo ezimfutshane) - naziphi na ezinye gymnosperms.

pores pollen okanye isibi uthuli - oko microspores, indawo apho - pollen malu. Kuyinto umoya wabo uthwele gametophyte ababhinqileyo. Le Ovule iyaphuhliswa sele megaspory. Ekukhulelweni le gamete Ovule inkunzi iba imbewu. A isici esasenza gametophyte nemazi - ukuxhathisa emzimbeni. Imbewu le ijikelezwe uvimba zizondlo, esebenzisa elilodwa kwi inkqubo ukuntshula, kodwa ngaphambi kokuqala imiqathango efanelekileyo imbewu ihleli sikarhulumente cwaka. Iziqhamo ayenziwanga ukusekwa, kodwa imbewu iyakwazi nokuphuhlisa ezahlukeneyo izixhobo.