{"id":665,"date":"2021-04-28T13:09:03","date_gmt":"2021-04-28T11:09:03","guid":{"rendered":"https:\/\/tydenikobydleni.cz\/?p=665"},"modified":"2021-07-09T23:50:53","modified_gmt":"2021-07-09T21:50:53","slug":"zazrak-skryty-v-seminku","status":"publish","type":"post","link":"https:\/\/tydenikobydleni.cz\/?p=665","title":{"rendered":"Z\u00e1zrak skryt\u00fd v sem\u00ednku"},"content":{"rendered":"\n

V semenech rostlin se mo\u017en\u00e1 skr\u00fdv\u00e1 tajemstv\u00ed nesmrtelnosti. No navzdory intenzivn\u00edmu v\u00fdzkumu z\u016fst\u00e1v\u00e1 mnoho z\u00e1had st\u00e1le zahalen\u00fdch rou\u0161kou tajemstv\u00ed.<\/p>\n\n\n\n

Jaro je v pln\u00e9m proudu a ze zem\u011b vyh\u00e1n\u00ed mlad\u00e9 zelen\u00e9 v\u00fdhonky. Zat\u00edmco prvn\u00ed z nich pat\u0159\u00ed hlavn\u011b trvalk\u00e1m, jednolet\u00e9 rostliny si mus\u00ed na svou sez\u00f3nu je\u0161t\u011b po\u010dkat. Jejich \u017eivot se ka\u017edoro\u010dn\u011b obnovuje ze semene, kter\u00e9 v sob\u011b skr\u00fdv\u00e1 z\u00e1rodek budouc\u00ed rostliny.<\/p>\n\n\n\n

Semeno vzniklo v evoluci jako dokonal\u00fd zp\u016fsob p\u0159e\u017eit\u00ed nep\u0159\u00edzniv\u00fdch podm\u00ednek, zp\u016fsob rozmno\u017eov\u00e1n\u00ed a z\u00e1rove\u0148 i zakonzervov\u00e1n\u00ed genetick\u00e9 rozmanitosti, kterou do ka\u017ed\u00e9ho sem\u00ednka p\u0159in\u00e1\u0161ej\u00ed rodi\u010dovsk\u00e9 geny. Semena obsahuj\u00ed z\u00e1soby pro prvn\u00ed hodiny, dny a\u017e t\u00fddny \u017eivota kl\u00ed\u010denca, podobn\u011b jako vejce pt\u00e1k\u016f \u010di plaz\u016f, na rozd\u00edl od vajec je v\u0161ak v\u011bt\u0161ina semen schopna zachov\u00e1vat si relativn\u011b dlouhou \u017eivotaschopnost.<\/p>\n\n\n\n

Ne v\u0161echny pro\u017e\u00edvaj\u00ed
Schopnost semen pro\u017e\u00edvat i del\u0161\u00ed nep\u0159\u00edzniv\u00e9 obdob\u00ed je v\u00fdlu\u010dn\u011b vlastnost\u00ed tzv. ortodoxn\u00edch semen, p\u0159i kter\u00fdch doch\u00e1z\u00ed k postupn\u00e9mu vysu\u0161ov\u00e1n\u00ed a vykl\u00ed\u010d\u00ed a\u017e ve vhodn\u00fdch podm\u00ednk\u00e1ch, \u010d\u00edm\u017e p\u0159ipom\u00ednaj\u00ed sp\u00f3ry bakteri\u00ed. Bu\u0148ky semen se na klidov\u00fd re\u017eim p\u0159ipravuj\u00ed ji\u017e b\u011bhem zr\u00e1n\u00ed a krom\u011b z\u00e1sobn\u00edch l\u00e1tek hromad\u00ed i mnoh\u00e9 metabolity s antioxida\u010dn\u00edmi vlastnostmi.<\/p>\n\n\n\n

V klidov\u00e9m stavu sn\u00e1\u0161ej\u00ed i extr\u00e9mn\u00ed nep\u0159\u00edzniv\u00e9 podm\u00ednky, ty v\u0161ak postupn\u011b ub\u00edraj\u00ed z jejich \u017eivotnosti. P\u0159esto\u017ee je obsah vody v mnoha semenech redukovan\u00fd jen na p\u00e1r procent, semena \u017eij\u00ed, d\u00fdchaj\u00ed a aktivn\u011b se br\u00e1n\u00ed po\u0161kozen\u00ed. Krom\u011b p\u0159\u00edtomnosti oxidac\u00ed po\u0161kozen\u00fdch molekul (zejm\u00e9na DNA a protein\u016f), kter\u00e9 t\u00edm ztratily svou funk\u010dnost, se jako podstatn\u00e9 jev\u00ed nahromad\u011bn\u00ed zplodin metabolismu, zejm\u00e9na kyanidu.<\/p>\n\n\n\n

Kapacita ochrann\u00fdch a obrann\u00fdch mechanism\u016f je v\u0161ak omezen\u00e1 a pokud dojde k jejich vy\u010derp\u00e1n\u00ed, po\u0161kozen\u00ed je nevratn\u00e9 a semeno ztr\u00e1c\u00ed kl\u00ed\u010divost. Z\u00e1chrannou brzdou pro st\u00e1rnouc\u00ed semeno je tzv. priming – semen\u016fm se umo\u017en\u00ed trochu nabobtnat a pak se znovu vysu\u0161\u00ed. Kr\u00e1tkodob\u011b zv\u00fd\u0161en\u00fd obsah vody umo\u017en\u00ed rozb\u011bhnut\u00ed repara\u010dn\u00edch proces\u016f, kter\u00e9 poopravit nejz\u00e1va\u017en\u011bj\u0161\u00ed po\u0161kozen\u00ed a semeno je (t\u00e9m\u011b\u0159) jako nov\u00e9.<\/p>\n\n\n\n

Mnoh\u00e9 ko\u0159en\u00ed jsou semeny exotick\u00fdch rostlin<\/p>\n\n\n\n

Nejdel\u0161\u00ed „sp\u00e1nek“
Dlouhov\u011bkost semen je druhov\u011b z\u00e1visl\u00e1, co\u017e umo\u017e\u0148uje hled\u00e1n\u00ed l\u00e1tek a proces\u016f, kter\u00e9 p\u0159e\u017e\u00edv\u00e1n\u00ed v tomto klidov\u00e9m stavu umo\u017e\u0148uj\u00ed. Ty by mohly pomoci i p\u0159i aplikaci v oblasti kosmick\u00e9 medic\u00edny, zejm\u00e9na p\u0159i p\u0159\u00edprav\u011b na dlouh\u00e9 meziplanet\u00e1rn\u00ed lety. P\u0159ed dv\u011bma lety se na str\u00e1nky jednoho z nejpresti\u017en\u011bj\u0161\u00edch v\u011bdeck\u00fdch \u010dasopis\u016f, Science, dostala dech vyr\u00e1\u017eej\u00edc\u00ed zpr\u00e1va, \u017ee jedno ze t\u0159\u00ed dva tis\u00edce let star\u00fdch semen datlovn\u00edku vykl\u00ed\u010dila.<\/p>\n\n\n\n

Sv\u00fdm v\u011bkem tato semena z Masada p\u0159ekonali Tis\u00edc t\u0159i sta let star\u00e9 \u017eiv\u00e9 semeno posv\u00e1tn\u00e9ho lotosu indick\u00e9ho (Nelumbo nucifera). P\u0159edpokl\u00e1d\u00e1 se, \u017ee semena datlovn\u00edku se zachovaly d\u00edky extr\u00e9mn\u011b such\u00fdm a hork\u00fdm podm\u00ednk\u00e1m v bl\u00edzkosti Mrtv\u00e9ho mo\u0159e. Najsenza\u010dnej\u0161\u00edm objevem z\u016fst\u00e1vaj\u00ed minim\u00e1ln\u011b deset tis\u00edc let star\u00e9 semena vl\u010d\u00edho bobu (Lupinus arcticus), kter\u00e9 se v roce 1967 na\u0161li v Yukonu ve vrstv\u00e1ch z obdob\u00ed pleistoc\u00e9nu.<\/p>\n\n\n\n

Za p\u0159e\u017eit\u00ed ur\u010dit\u011b vd\u011b\u010dili i v\u011b\u010dn\u011b zmrzl\u00e9 p\u016fd\u011b seversk\u00e9 tundry. P\u0159esto\u017ee se postupn\u011b da\u0159\u00ed mapovat podstatu dlouhov\u011bkosti semen, k jej\u00edmu skute\u010dn\u00e9mu porozum\u011bn\u00ed je st\u00e1le daleko. V\u00edme v\u0161ak s ur\u010ditost\u00ed, \u017ee semena hrachu ovliv\u0148uj\u00ed dlouhov\u011bkost J\u00e1no\u0161\u00edkov.<\/p>\n\n\n\n

Kdy\u017e se kl\u00ed\u010dit ned\u00e1
V\u011bt\u0161ina semen nedok\u00e1\u017ee hned po sv\u00e9m dozr\u00e1n\u00ed vykl\u00ed\u010dit, a\u010dkoli jsou na to „fyzicky a psychicky“ (rozum\u011bj anatomicky a metabolicky) nachystan\u00e9 a v okol\u00ed vl\u00e1dnou ide\u00e1ln\u00ed podm\u00ednky. Tento stav je b\u011b\u017en\u00fd zejm\u00e9na pro semena plan\u011b rostouc\u00edch rostlin, kde tato tzv. dormance zabra\u0148uje semeni vykl\u00ed\u010dit mimo sez\u00f3ny (nap\u0159\u00edklad na podzim), umo\u017e\u0148uje jim p\u0159e\u010dkat obdob\u00ed nep\u0159\u00edzniv\u00e9 pro jejich v\u00fdvoj, ale i r\u016fzn\u00e9 p\u0159\u00edrodn\u00ed katastrofy.<\/p>\n\n\n\n

\"\"<\/figure><\/div>\n\n\n\n

Dormanci v\u011bt\u0161iny semen navozuj\u00ed i \u200b\u200bodstra\u0148uj\u00ed rostlinn\u00e9 hormony, jejich\u017e hladiny reaguj\u00ed nap\u0159\u00edklad i na \u010das od dozr\u00e1n\u00ed, na obdob\u00ed chladu nebo na mr\u00e1z. Za „spavou nemoc“ n\u011bkter\u00fdch semen jsou zodpov\u011bdn\u00e9 jejich obaly, kter\u00e9 jim br\u00e1n\u00ed reagovat na vlhkost a teplotu a nakonec i kl\u00ed\u010dit.<\/p>\n\n\n\n

N\u011bkter\u00e9 obaly semen mus\u00ed shn\u00edt, jin\u00e9 mus\u00ed po\u0161kodit pt\u00e1ky, jin\u00fdm pom\u016f\u017ee \u00famysln\u00fd lidsk\u00fd z\u00e1sah (skarifikace), ale n\u011bkter\u00fdm jen ohe\u0148. A\u017e po\u017e\u00e1r uvoln\u00ed semena ze speci\u00e1ln\u011b zavoskovan\u00fdch \u0161i\u0161ek borovic, kter\u00e9 se ob\u010das objevuj\u00ed na stromech v Yellowstonsk\u00e9m n\u00e1rodn\u00edm parku, aby po po\u017e\u00e1ru daly z\u00e1klad nov\u00e9mu lesu.<\/p>\n\n\n\n

Nejnov\u011bji se zjistilo, \u017ee samotn\u00fd kou\u0159 obsahuje slou\u010deninu (butenolid), co um\u00ed spavou nemoc semen vyl\u00e9\u010dit a ohe\u0148 tak dok\u00e1\u017ee nejen teplem, ale i biochemick\u00fdmi mechanismy navodit kl\u00ed\u010den\u00ed, a trochu po sob\u011b zahladit spou\u0161\u0165, co nad\u011blal.<\/p>\n\n\n\n

Ne v\u0161echny semena jsou drobn\u00e9. P\u0159\u00edkladem je nap\u0159\u00edklad avok\u00e1do \u010di mango<\/p>\n\n\n\n

Jen jedna \u0161ance
Kdy\u017e se semeno „zbav\u00ed“ dormance a je st\u00e1le \u017eivotaschopn\u00e9, na kl\u00ed\u010den\u00ed pot\u0159ebuje hlavn\u011b optim\u00e1ln\u00ed vlhkost a teplotu. Ka\u017ed\u00fd rostlinn\u00fd druh si na kl\u00ed\u010den\u00ed vy\u017eaduje trochu jin\u00e9 vn\u011bj\u0161\u00ed podm\u00ednky, p\u0159i\u010dem\u017e nap\u0159\u00edklad drobn\u00e9 sem\u00ednka si obvykle potrp\u00ed na sv\u011btlo – bez n\u011bj nevykl\u00ed\u010d\u00ed.<\/p>\n","protected":false},"excerpt":{"rendered":"

V semenech rostlin se mo\u017en\u00e1 skr\u00fdv\u00e1 tajemstv\u00ed nesmrtelnosti. No navzdory intenzivn\u00edmu v\u00fdzkumu z\u016fst\u00e1v\u00e1 mnoho z\u00e1had st\u00e1le zahalen\u00fdch rou\u0161kou tajemstv\u00ed. Jaro je v pln\u00e9m proudu a ze zem\u011b vyh\u00e1n\u00ed mlad\u00e9 zelen\u00e9 v\u00fdhonky. Zat\u00edmco prvn\u00ed z nich pat\u0159\u00ed hlavn\u011b trvalk\u00e1m, jednolet\u00e9 rostliny si mus\u00ed na svou sez\u00f3nu je\u0161t\u011b po\u010dkat. Jejich \u017eivot se ka\u017edoro\u010dn\u011b obnovuje ze semene, kter\u00e9 […]<\/p>\n","protected":false},"author":1,"featured_media":666,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"tdm_status":"","tdm_grid_status":"","footnotes":""},"categories":[38],"tags":[],"class_list":["post-665","post","type-post","status-publish","format-standard","has-post-thumbnail","category-bydleni"],"_links":{"self":[{"href":"https:\/\/tydenikobydleni.cz\/index.php?rest_route=\/wp\/v2\/posts\/665","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/tydenikobydleni.cz\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/tydenikobydleni.cz\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/tydenikobydleni.cz\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/tydenikobydleni.cz\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=665"}],"version-history":[{"count":0,"href":"https:\/\/tydenikobydleni.cz\/index.php?rest_route=\/wp\/v2\/posts\/665\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/tydenikobydleni.cz\/index.php?rest_route=\/wp\/v2\/media\/666"}],"wp:attachment":[{"href":"https:\/\/tydenikobydleni.cz\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=665"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/tydenikobydleni.cz\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=665"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/tydenikobydleni.cz\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=665"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}