Masarautar tsire-tsire ta haɓaka dabaru daban-daban don rayuwa. Wasu ana iya ganinsu, kamar su murtsattsun guragu a misali, waɗanda ba komai ba ne face ganyayyaki da aka sauya waɗanda suka maye gurbin ikon iya yin hotuna da na kare jikin waɗannan tsire-tsire. Amma akwai wasu da ba haka bane, kamar abin da ake kira C4 shuke-shuke.
Su shuke-shuke ne gabaɗaya suna rayuwa a cikin busassun yankuna masu bushe-bushe, don haka sun samo asali ne don rage asarar carbon dioxide (CO2) yayin daukar hoto, tunda wannan gas ne mai mahimmanci yayin aiwatar da canza hasken rana zuwa abincin tsirrai.
Hoto na hoto na tsire-tsire na C4
Hoton - Wikimedia / Ninghui Shi
Don ƙarin fahimtar shuke-shuke C4, da farko za mu fara bayanin hotunan hoto da muka fi sani, galibi saboda shi ne wanda aka yi karatu daga makaranta, C3. Shin ya ƙunshi shan hasken rana da carbon dioxide ta cikin chloroplasts na ƙwayoyin samu a cikin kore ko sassan hotuna masu kyawu, da ruwa daga asalinsu, don canza shi zuwa abinci ta hanyar jerin abubuwan sinadarai.
Da farko, wannan kuzarin haske yana canzawa zuwa makamashin sunadarai, kasancewar kwayoyin NADPH (nicotin adenine dinucleotide phosphate) da ATP (adenosine triphosphate, farkon wanda suka adana shi. Amma daga baya, waɗannan ƙwayoyin suna hada sinadarin kara kuzari kamar yadda carbon dioxide ya ragu.
Mataki na karshe na wannan aikin shine lokacin da tsire-tsire ke amfani da makamashin da suka tara a rana don gyara carbon daga carbon dioxide a cikin hanyar glucose. Wannan wani bangare ne na zagawar Calvin.
Pero photosynthesis a cikin tsire-tsire C4 daban. Suna da nau'ikan chloroplasts guda biyu. Wasu suna kusa da tasoshin gudanarwa (muna iya cewa sun yi daidai da jijiyoyin dabbobi), wasu kuma ana samunsu a cikin ƙwayoyin chlorophyll parenchyma na gefe, waɗanda sune waɗanda suka fi kusa da gefen ganye. Na karshen kuma ana kiransu kwayoyin mesophilic, kuma sune wadanda suke da chloroplasts wadanda zasu gyara carbon dioxide tare da taimakon kwayar PEPA (phosphoenolpyruvic acid) da enzyme phosphoenolpyruvate carboxylase.
Daga waɗannan kwayoyin, za a samar da oxaloacetic acid, wanda ya kunshi carbons 4 (wanda shine dalilin da ya sa aka san su da shuke-shuke na C4). Wannan sai a canza shi zuwa malic acid, kuma wannan shine lokacin da ya wuce zuwa chloroplasts wanda ke ɗauke da ƙwayoyin ciki na jigilar jiragen ruwa ta cikin plasmodesmata (waɗannan su ne tsarin da bangon da ke kewaye da kwayar halitta, cytoplasm, yake da shi). A cikin su, za a saki CO2, kuma sake zagayowar Calvin na iya ci gaba.
Yanayi da shuke-shuke C4
Shuke-shuke da ke rayuwa a wurare masu zafi da bushe suna da matsala fiye da sauran don kauce wa asarar ruwa. Amma don rayuwa dole ne ku numfasa, kuma yin hakan babu makawa rasa ruwa. Sabili da haka, lokacin da yanayin zafi yayi yawa, stomata (pores) na ganyayyakin suna rufewa, kuma ta yin hakan iskar oxygen da ake samu a lokacin hoton fure yana ƙaruwa.
A cikin yanayi na al'ada, lokacin da adadin oxygen da carbon dioxide suka daidaita, enzyme ɗin da ke da alhakin gyaran carbon (RuBisCO) na iya cika aikinsa ba tare da matsala ba. Amma lokacin da maida hankali akan CO2 yayi ƙasa da na oxygen, wannan enzyme ne ke haifar da gas na ƙarshe ba CO2 ba, wanda shine abin da ke faruwa a shuke-shuke na C4.
Waɗannan na musamman ne, saboda ban da samun nau'ikan chloroplasts guda biyu (duba sashe na sama), enzyme phosphoenolpyruvate carboxylase, wanda yana ɗaya daga cikin waɗanda ke da hannu a gyaran carbon, yana tallafawa ɗimbin iskar oxygen.
Menene fa'idodin shuke-shuke C4?
Akwai fa'idodi masu mahimmanci da yawa waɗanda waɗannan tsire-tsire suke da su:
- Yawancin lokaci, girma da sauri fiye da tsire-tsire C3.
- Suna yin amfani da carbon da kyau, ko dai don samar da ƙarin tushen da / ko ƙarin ganye.
- Rasa karancin ruwa yayin daukar hoto (kamar yadda wannan labarin, an kiyasta cewa sun rasa kwayoyin ruwa 277 na kowane kwayoyin CO2, yayin da shuke-shuke C3 suka rasa kwayoyin ruwa 833 ga kowane daya daga cikin CO2 da suka gyara).
- Bunkasa samar da glucose, wanda shine karshen sakamakon photosynthesis.
- Za su iya zama a ƙasar da ƙarancin ruwa yake.
Duk waɗannan dalilan, suna daɗa zama mai ban sha'awa, musamman don girma a cikin yanayin busassun.
Menene tsire-tsire C4?
Akwai tsire-tsire masu yawa waɗanda ke aiwatar da hotuna na C4. Misali, masara, ciyawa, amarantar, kanwa, dawa, ko hatsin rai. Waɗannan su ne waɗanda ke da ƙananan kyallen takarda kamar waɗanda suka samo asali daga yanayin yanayi mai zafi, kamar su maples ko camellias.
Sabili da haka, sanin su na iya zama da amfani ƙwarai don sanin abin da ya kamata a bunƙasa a yankunan da babu wadatar ruwa sosai.