Ubukumkani bezityalo buvelise iindlela ezahlukeneyo zokuphila. Ezinye ziyabonakala, ezinje nge-cactus spines umzekelo, ezingezizo ngaphandle kwamagqabi aguquliweyo atshintshe amandla e-photosynthesize kunye nokukhusela umzimba walezi zityalo. Kodwa kukho ezinye ezingekhoyo, ezinje ngokuba zibizwa njalo C4 izityalo.
Zizityalo ezihlala ngokubanzi kwimimandla eyomileyo okanye eyomileyo ziye zavela ukuze zinciphise ukulahleka kwekhabhon diokside (CO2) ngexesha lefotosinthesisKuba le irhasi ebalulekileyo ngexesha lokuguqula amandla elanga abe kukutya kwezityalo.
Iimpawu zefotosinthesisi yezityalo zeC4
Umfanekiso - Wikimedia / Ninghui Shi
Ukuqonda ngcono izityalo zeC4, siza kuqala sichaze ifotosinthesisi esiyazi ngcono, ngakumbi kuba yile ifundwayo esikolweni, iC3. Ngaba iquka ukufunxeka kwamandla elanga kunye nekhabhon diokside ngokusebenzisa ii-chloroplast zeeseli ifunyenwe kwiindawo eziluhlaza okanye kwi-photosynthetic yezityalo, kunye namanzi avela ezingcanjini, ukuyiguqula ibe kukutya ngothotho lweempendulo zamachiza.
Ekuqaleni, la mandla okukhanya atshintsha amandla emichiza, kuba ziimolekyuli zeNADPH (nicotin adenine dinucleotide phosphate) kunye neATP (adenosine triphosphate, eyokuqala ukuyigcina. zidibanisa ii-carbohydrate njengoko icarbon dioxide incitshisiwe.
Inqanaba lokugqibela lale nkqubo kuxa izityalo zisebenzisa amandla eziwafumeneyo emini ukulungisa ikhabhon ye-carbon dioxide ekwimo yeglucose. Le yinxalenye yomjikelo kaCalvin.
Kodwa ifotosinthesisi kwizityalo zeC4 yahlukile. Zineendidi ezimbini zeekloroplast. Ezinye zikufuphi neenqanawa zokuqhuba (singatsho ukuba ziyalingana nemithambo yezilwanyana), kwaye ezinye zifumaneka kwiiseli zecarlipllal parenchyma, ezo zikufutshane nemida yamagqabi. Ezi zokugqibela zikwabizwa ngokuba ziiseli zemesophilic, kwaye zezo zinee-chloroplast eziza kulungisa i-carbon dioxide ngoncedo lwe-PEPA (phosphoenolpyruvic acid) molecule kunye ne-enzyme phosphoenolpyruvate carboxylase.
Ukusuka kwezi molekyuli, i-oxaloacetic acid iya kuveliswa, eyilwe ziikhabhoni ezi-4 (yiyo loo nto zisaziwa njengezityalo zeC4). Oku ke kuguqulwa kube yi-malic acid, kwaye kulapho ke idlulela kwii-chloroplast eziqulathe iiseli zangaphakathi zeenqanawa eziqhutywa ngeplasmodesmata (ezi zizinto ezenziwa ludonga olujikeleze iseli yesisele, i-cytoplasm). Kuzo, i-CO2 iya kukhutshwa, kwaye umjikelo kaCalvin ungaqhubeka.
Imozulu nezityalo C4
Izityalo ezihlala kwindawo ezishushu nezomileyo zinobunzima ngakumbi kunezinye ukuthintela ukulahleka kwamanzi. Kodwa ukuze uphile kufuneka uphefumle, kwaye ngokwenza njalo akunakuphepheka ukuphulukana namanzi. Ke ngoko, xa amaqondo obushushu ephezulu, i-stomata (pores) yamagqabi iyavalwa, kwaye ngokwenza njalo ioksijini eveliswa ngephotosynthesis yonyusa uxinzelelo lwayo.
Kwiimeko eziqhelekileyo, xa inani leoksijini kunye nekhabhoniyokhaladi ilinganisiwe, i-enzyme enoxanduva lokulungisa ikhabhon (i-RuBisCO) inokuwenza umsebenzi wayo ngaphandle kwengxaki. Kodwa xa uxinizelelo lwe-CO2 lusezantsi kunolo lweoksijini, le enzyme inceda le gesi yokugqibela hayi i-CO2, Yinto eyenzekayo kwizityalo zeC4.
Ezi zikhetheke kakhulu, kuba ukongeza ekubeni uneentlobo ezimbini zeekloroplast (jonga icandelo eliphezulu), i-enzyme phosphoenolpyruvate carboxylase, yenye yezo zibandakanyeka kulungiso lwekhabhoni, ixhasa uxinzelelo oluphezulu lweoksijini.
Zithini izibonelelo zezityalo zeC4?
Kukho izibonelelo ezininzi ezibalulekileyo ezinazo:
- Ngokuqhelekileyo, khula ngokukhawuleza kunezityalo zeC3.
- Basebenzisa ngcono ikhabhon, nokuba uvelise ezinye iingcambu kunye / okanye amagqabi amaninzi.
- Ukuphulukana namanzi amancinci Ngexesha lefotosinthesisi (ngokwe Oku kubhaliwe, Kuqikelelwa ukuba balahlekelwa ziimolekyuli zamanzi ezingama-277 kwimolekyuli nganye ye-CO2, ngelixa izityalo zeC3 zilahlekelwa ziimolekyuli zamanzi ezingama-833 nganye ye-CO2 abayilungisayo).
- Ukukhuthaza imveliso yeglucose, esisiphumo sokuphela kwefotosinthesisi.
- Banokuhlala emhlabeni apho kukho amanzi amancinci.
Kuzo zonke ezi zizathu, ziya zisiba ngakumbi nangakumbi, ngakumbi ngokukhula kwiindawo ezomileyo.
Yintoni izityalo zeC4?
Zininzi izityalo ezenza i-C4 photosynthesis. Umzekelo, umbona, ingca, amaranth, umoba, amazimba okanye irye. Zizo ezinezicubu ezincinci ezixineneyo kunezo zivela kwimozulu epholileyo, ezinje ngeemaphu okanye iicamellias.
Ke ngoko, ukubazi kunokuba luncedo kakhulu ukwazi ukuba ungakhulisa ntoni kwiindawo ezinamanzi amancinci.