Frideta Seidlová

The anatomy of the shoot apex of wheat (Triticutn aestivum L.) during transition from the vegetative to the reproductive state and the determination of the primordia

An investigation was made of the anatomical structure of the shoot apex of wheat in the first four stages of organogenesis according toKuperman (1961). It was found that the shoot apex is first covered only with dermatogen (first stage). Then the hypodermis gradually differentiates (second stage) followed by differentiation of the subhypodermis (third stage). In the first stage, the central core of the apex is formed by more or less uniform isodiametric cells so that no zones are distinguishable. During the initiation of the primordia of the assimilating leaves, i.e. in the second stage, a group of larger cells was observed in the apical part of the hypodermis and can be compared with the central zone described in dicotyledons. Under it there is a characteristic group of smaller cells. In the third stage the differences between these groups of cells become less clear and in the fourth stage are no longer observable. No differences were found in the manner of initiating the leaf and bud primordia during the period of ontogenesis studied. There is, however, an alteration in the extent of growth between the bud primordium and the corresponding leaves. Short-day photoperiodic inhibition, always started on the days when the shoot apices were collected for anatomical study, showed that the determination of the primordia of the leaves and axillary buds as parts of the inflorescence is complete by the end of the third stage, at the time when the primordia in the central part of the ear are initiatedAbstractSledovali jsme vývoj anatomické stavby vzrostného vrcholu pšenice v prvních čtyřech etapách organogeneze podleKupermanové (1961). Zjistili jsme, že na vzrostném vrcholu zprvu krytém jen dermatogenem (v 1. etapě) se postupně vytváří hypodermis (v 2. etapě) a subhypodermis (ve 3. etapě). Centrální dřeň vrcholu je v 1. etapě tvořena přibližně stejnými, isodiametrickými buňkami, takže zde není patrná žádná zonace. Při zákládání asimilačních listů, tj. ve 2. etapě jsme pozorovali v apikální části hypodermis skupinu větších buněk, kterou lze srovnávat s centrální zónou popsanou u dvouděložných rostlin, a pod ní charakteristickou skupinu menších buněk. Ve 3. etapě se rozdíly mezi těmito skupinami buněk stírají a ve 4. etapě mizí. Nezjistili jsme rozdíly ve způsobu zákládání listů a pupenů během ontogeneze. Mění se však vztah mezi základy pupenů a okolních listů.Fotoperiodickou krátkodenní inhibicí, započatou vždy ve dnech odběrů vzrostných vrcholů pro sledování anatomické struktury, jsme zjistili, že determinace listů a úžlabních pupenů jako částí květenství je úplná až na konci 3. etapy, tj. v době zakládání primordií ve střední časti klasu.Abstractлеслелолось развитие анатомиуеской структкуры конуеа нарастания шценицы Я. Опатрна, ϕ.Сайдлова, к.Бенеш, лнститут экспериментальной ботаники ЧСАН, в первых этапах органогенеза по куперман. Сначала конус нарастания покрыт тлько дерматогеном (1-ый этап органогенеза). На первом зтапе центральная часть конуса нарастания состоит из почти одинаковых изодиаметрических клеток, такчто никаких зон отличить группу более крупных клеток в гиподермисе. Этагруппа напоминает центральную зону описанную у двудольных растений. Под ней находися хароктеристичестич еская группа более мелких клеток. В течение 3-его этапа

Change of growth correlations in the shoot meristem as the cause of age dependence of flowering in Chenopodium rubrum

Summary Three, six and nine days old seedlings of the short-day plant Chenopodium rubrum show marked differences in the number of inductive cycles they need to evoke floral differentiation. The older the plants, the more inductive cycles and the longer the time required for flowering. We have compared the changes in the anatomical structure of the shoot apex and in the growth of leaf and bud primordia in the age groups mentioned. The speed of floral differentiation does not correlate with the zonal pattern of the shoot apex before induction. Floral differentiation is, however, influenced by the amount of meristematic tissue and the number of leaves initiated. Photoperiodic treatment causes an immediate inhibition of leaf growth in all age groups and, soon after, a release from apical dominance in the apex. Consequently, branching of the shoot apex occurs and the growth of leaf primordia is inhibited. Finally, formation of new leaves in the peripheral zone ceases and differentiation of the terminal flower takes place. If the number of inductive cycles is insufficient, restored leaf organogenesis and a correlated inhibition of bud primordia resume, and a reversal to the vegetative state sets in. The manner of initiation of the lateral organs — leaves and buds — is similar in plants of various age. There are, however, quantitative differences in the number and growth of the lateral organs at the onset of photoperiodic induction as well as during induction and during postinductive changes. These differences in growth cause differences in the number of inductive short-day cycles required for inhibition of vegetative growth and the changes leading to flowering. In younger plants having less well-developed vegetative growth, a single photoperiodic cycle is sufficient to induce flower formation. In older plants a single cycle results in an initial change of the growth correlations between leaf and bud primorida, i.e. in branching, while further floral differentiation requires repeated photoperiodic cycles. Thus, with Chenopodium rubrum the importance of the suppression of leaf growth during the transition from the vegetative to the reproductive state may be demonstrated.

Development of the shoot apex ofChenopodium rubrum L. after photoperiodic induction in the cotyledon stage

Development of the shoot apex up to floral differentiation was investigated in the short-day plantChenopodium rubrum. The changes occurring in the apex from energence until full opening of the cotyledons (Figs 1–4), development during photoperiodic induction (Figs. 5–8), as well as the resulting floral differentiation (Figs. 9–10) are described. It was aimed at excluding the influence of plastochron changes on the interpretation of ontogeny of the shoot apex. For that reason two planes of longitudinal sections and two plastochron stages were compared.In young plants zonation does not become fully evident prior to floral differentiation. The anatomical structure of the shoot apex does not change substantially during the first two inductive cycles which proved to be obligatory under the given experimental conditions. The changes occurring during two further inductive cycles correspond to the total activation of the meristems as manifested by the growth and branching of the apex preceeding floral differentiation proper.AbstractU krátkodenní rostlinyChenopodium rubrum jsme sledovaly vývoj vzrostného vrcholu až ke květní diferenciaci. Byly popsány změny vzrostného vrcholu této rostliny od klíčení až do plného rozevření děloh (obr. 1 až 4), vývoj vrcholu během následující fotoperiodické indukce (obr. 5 až 8) a výsledná květní diferenciace (obr. 9 a 10). Snažily jsme se vyloučit vliv plastochronových změn na interpretaci ontogenese vzrostného vrcholu. Proto jsme srovnávaly vždy dvě roviny podélných řezů a dvě fáze plastochronu.Bylo zjištěno, že u mladých rostlin se zonace nestačí dokonale projevit před květní diferenciací. Během prvních dvou indukčních cyklů, které byly v našich podmínkách pro květní indukei obligátní, zůstává anatomická struktura vzrostného vrcholu přibližně stejná. Změny během dalších dvou indukčních cyklů odpovídají celkové aktivaci meristemu, projevující se jako růst a větvení vrcholu, které předchází vlastní květní diferenciaci.AbstractУ короткодневного растенияChenopodium rubrum иссдедовали развитие конуса нарастания до генеративной дифференциации. Описаны изменения конуса нарастания от прорастания до раскрытия семядолей (рис с—4), развитие конуса нарастания во время фотопериодической индукции (рис 5–8) и генеративная диференциация (рис. 9, 10). Ввиду того, что мы стремились исключить влияние пластохроных изменений на интерпретацию онтогенеза конуса нарастания во всех случаях сравнивались продольные срезы в двух взаимно перпендикулярных плоскостях в двух пластохроных фазах.Установлено, что у молодых растений отчетливое отграничение зон не успевает произойти до генеративной дифференциации. Во время первых двух циклов индукции, необходимых для генеративной дифференцииации в условиях опыта, анатомическая структура конуса нарастаниостается приблизительно одинаковой. Изменения во время следующих двух циклов индукций выражают общую активацию меристемы. Это проявляется в росте и ветвлении конуса перед генеративной дифференциацией.

Transgenic tobacco plants with T-DNA phytohormone synthesis genes

Agrobacterium tumefaciens binary vectors carrying kanamycin resistance gene and either C58 T-DNA gene 4 for cytokinin synthesis or genes 1 and 2 for auxin synthesis were constructed and used for transformation of a short-day tobacco Maryland Mammoth. Kanamycin resistant plants were regenerated from a small fraction of transformed tissue and the presence of T-DNA in their genome was verified by Southern blotting. The level of endogenous cytokinin in plants transgenic for gene 4 and the level of endogenous IAA in those transgenic for genes 1 and 2 increased by more than 100 %. A number of morphological characteristics distinguish them from untransformed controls.

Time-dependence of auxin and ethrel effects on flowering in chenopodium rubrum L.

IAA, NAA and ethrel (1 × 10-4M and 3 × 10-4M) was applied to the plumula of Chenopodium plants at different time after the start of photoperiodic treatment and the flowering response was investigated. The inhibitory effect was found with all the applications during the first two days, whereas a stimulatory one on the third and fourth day. We assume this dual effect reflects the differences attained in developmental phase and in the degree of shoot apex differentiation.

Floral and growth responses in Chenopodium rubrum L. to an extract from flowering Nicotiana tabacum L.

Flowering of Chenopodium rubrum seedling plants was obtained in continuous light after application of fractions of a partially purified extract from leaves of flowering Maryland Mammoth tobacco (Nicotiana tabacum). The stage of flowal differentiation was dependent on the age of the Chenopodium plants used for the bioassay. Apices of plants treated with the extract at the age of four or seven days showed an advanced branching of the meristem or the beginning of formation of a terminal flower; treatment with the extract of plants 12 d old resulted in rapid formation of flower buds in all assay plants. Non-treated control plants kept in continuous light remained fully vegetative. The effects of the extract on flowering were associated with pronounced growth effects. Floral differentiation was preceeded by elongation of the shoot apex. Extension of all axial organs occurred, while growth of leaves, including leaf primordia, was inhibited. The pattern of growth after application of the flower-inducing substance(s) did not resemble the effects of the known phytohormones, but showed some similarities to growth changes resulting from photoperiodic induction of flowering.

Growth correlations and rna synthesis in different parts of the shoot apical meristem ofChenopodium rubrunt L. induced to flowering

Uridine-3H incorporation and RNA concentration were investigated in different parts of the shoot apical meristem ofChenopodium rubrum using autoradiography and cytophotometry. A single inductive cycle was sufficient to bring about postinductive first events in the shoot apex but not for complete flower differentiation. The initial activation of RNA synthesis manifested itself in all zones of the apex. The first increase was more conspicuous in the peripheral than in the central zone. The indications of the first events in the apices after a single inductive cycle disappear prior to morphological reversal to the vegetative state. Induction by three short days led to rapid flower differentiation. The increase in RNA synthesis and concentration was most conspicuous in the central zone in this case. The ratio of RNA synthesis and content between bud and leaf primordia (B/L) also change in relation to photoperiodic induction. In vegetative plants the B/L ratio was low while after induction it increased.The shifts in activity of RNA synthesis observed in the shoot apical meristem are related to the changes in growth activity of the different parts of the apex. The growth ratios in the apices bear the character of growth correlations. The change in the growth correlations following photoperiodic induction together with the total activation of RNA synthesis are considered to represent one of the first events of the transition to the reproductive state.AbstractInkorporace uridinu-3H a koncentrace RNK byla studována v různych cástech osniho apikálniho meristemuChenopodium rubrum L. s použitim metod autoradiografie a cytofotometrie. Indukce jednim krátkym dnem postacila pro vyvoláni prvnich postinduktivnich projevàů, nikoliv pro liplnou květni diferenciaci. Poáčáteáčni aktivace syntézy RNK se projevila ve vsech zonách vrcholu. Zpoáčátku byl vzestup v periferni zonáě větáěi než v centrálni zoně, o den později se poměr inkorporaee uridinu a koncentrace RNK obrátil. Pred morfologickym zvratem do vegetativni fáze prvni postinduktivni projevy ve vrcholech mizi. Indukce tfemi krátkymi dny míla za následek rychlou květni diferenciaci. Zvyseni syntézy RNK a koncentrace RNK bylo největsi v centrálni zone. Poměr v syntéze RNK a v obsahu RNK mezi pupenovymi a listovymi primordii (B/L) se rovněz měnil podle fotoperiodické indukce. U vegetativních rostlin byl poměr B/L nízký, po indukei vzdy stoupal.Nalezené pfesuny v aktivitě syntézy RNK v rámci osniho vrcholového meristemu maji vztah k změnám v růstové aktivitě různych cásti vrcholů. Růstové poměry ve vrcholech maji Charakter růstovych korelaci. Změna růstovych korelaci po fotoperiodické indukei je vedle celkové aktivace syntézy RNK povazována za jeden z prvnich projevů pfechodu do reproduktivni fáze.

Growth effects of 2-thiouracil and possibility of selective inhibition of floral differentiation inChenopodium rubrum L.

The effect of 2-thiouracil on vegetative growth and floral differentiation was investigated inChenopodium rubrum plants grown in water cultures. Between the low concentrations of the agent, stimulating vegetative growth and floral differentiation, and those inhibiting both these processes, a narrow concentration range was found (1.10−5m to 2.10−5m), where growth was inhibited selectively. At a concentration of 1.10−4m a selective inhibition of development was found when 2-thiouracil was applied at the beginning of photoperiodic induction. Inhibition of development was strong regardless of whether 2-thiouracil was applied before, during or closely after 4 days of photoperiodic induction; the degree of growth inhibition, however, changed in dependence on photoperiodic induction. The strongest relative inhibition of development, calculated as a ratio between development and growth, was observed always at the beginning of photoperiodic induction.Investigation of plant growth as well as the anatomical and autoradiographic study after the application of 2-thiouracil indicate that the inhibition becomes evident at the end of 4 days of application by an overall growth inhibition and a decrease of mitotic activity. Reversal by uracil was possible after simultaneous application of 2-thiouracil. The nature of the selective inhibition is discussed and two possible interpretations of the data obtained are analyzed: a) different response of growth processes in apices and young vegetative organs respectively with regard to different participation of cell division and elongation, b) specific inhibition of floral differentiation.AbstractU rostlinChenopodium rubrum pěstovaných ve vodních kulturách jsme sledovali vliv 2-thiouracilu na vegetativní růst a květní diferenciaci. Mezi, slabými koncentracemi, které stimulovaly vegetativní růst a květní diferenciaci, a koncentracemi, které působily na oba pochody inhibičně, jsme našli úzké rozmezí koncentrací 1.10−5m až 2.10−5m, kdy byl inhibován vývoj selektivně. V koncentraci 1.10−4m se projevila selektivní inhibice vývoje, byl-li 2-thiouracil aplikován na začátku fotoperiodické indukce. Vlastní inhibice vývoje byla silná bez ohledu na aplikaci 2-thiouracilu uracilu před, během nebo těsně po čtyřdenní fotoperiodické induckei, inhibice růstu se však měnila v závislosti na fotoperiodické indukci. Nejsilnější relativní inhibice vývoje, vypočtena jako poměr mezi vývojem a růstem, byla vázána vždy na začátek, fotoperiodické indukce.Sledování růstu rostlin a také anatomický a autoradiografický obraz po aplikaci 2-thiouracilu ukazuje, že inhibice se začíná projevovat až ke konci čtyřdenní aplikace, a to celkovou inhibieí růstu a snížením mitotické aktivity. Reverse uracilem byla možná při jeho současném podání s 2-thiouracilem, nikoliv již po 24 hodinách. Je diskutována otázka podstaty selektivní inhibice a rozebrány 2 možné interpretace zjištěných fakt: a) různá reakce růstových pochodů ve vrcholech a mladých vegetativních orgánech s ohledem na různou účast pochodů dělení a prodlužování buněk, b) specifická inhibice květní diferenciace.AbstractИсследовалось влияние 2-тиоурацила на рост и дифференциацию цветковChenopodium rubrum L., выращиваемого в водных культурах. Между низкими концентрациями, стимулирующими рост и дифференциацию цветка и относительно высокими, подавляющими оба процесса, найден небольшой интервал концентраций 1.10−5m–2.10−5m, при которых селективно подавлялось одно развитие. Селективное подавление развития также происходило после применения 2-тиоурацила в концентрации 10−4m в начальном периоде фотопериодической индукции. Развитие подавлялось при применении 2-тиоурацила перед, в течение или непосредственно после четырехдневной фотопериодической индукции. Ингибиция роста изменялась в зависимости от фотопериодической индукции. Наиболее сильная относительная ингибиция, быраженная отношением между развитием и ростом, была связана во всех случаях с началом фотопериодической индукции.Наблюдения за ростом растений а также анатомические и авторадиографические исследования показывают, что ингибиция начинает проявляться лишь в конце четырехдневного применения, а именно как общее подавление роста и снижение митотической активности. Обратимость ингибиции при помощи урацила происходило лишь в случае одновременного применения с 2-тиоурацилом, при применении урацила спустя 24 часа после 2-тиоурацила уже не происходило снятие ингибиции. Рассматривается вопрос, на чем основывается селективная ингибиция и приводятся два возможные объяснения: а) различная реакция ростовых процессов в конусах нарастания и в молодых вегетативных органах ввиду различного участия процессов деления и удлинения клеток, б) специфическое подавление дифференциации цветка.

Relationships between the blade and sheath growth in the same leaf and in successive leaves of winter barley

Winter barley (Hordeum vulgare L. cv. Efra) plants were grown till the stage of the fourth leaf under controlled conditions at constant temperatures 26.0 °C, 21.8 °C, 19.6 °C and 15.3 °C. The relationships between the sheath and blade growth was studied. The leaf sheath began to be discernible when it was 0.1 mm long and the blade length was 20 mm. In this stage a correlation (r = 0.812) was found between the length of blade and that of shearth. The sheath length in 20 mm long leaf increased in dependence on leaf insertion. At the time of the beginning of sheath discernibility the elongation growth of the subsequent leaf was initiated. In this stage the sheath length and the length of the subsequent leaf were correlated (r = 0.911). At the beginning of the growth of the subsequent leaf the length of the preceding sheath increased in dependence on insertion. Other relations were derived graphically and a hypothetical model of relationships between the cereal leaf growth and development was formulated.

Floral transition as a sequence of growth changes in different components of the shoot apical meristem ofChenopodium rubrum

The changes in cell division rate were studied in different components of the shoot apex ofChenopodium rubrum during short-day photoperiodic induction and after the inductive treatments. Induced and vegetative apices were compared. Accumulation of metaphases by colchicine treatment was used to compare the mean cell cycle duration in different components of the apex. A direct method of evaluating the increase in cell number obtained by anticlinal or periclinal divisions was applied if the corresponding components of induced and non-induced apices had to be compared. The short-day treatment prolonged the cell cycle more in the peripheral zone than in the central zone and still more in the leaf primordia. The importance of changing growth relations for floral transition was shown particularly if the induced plants were compared with the vegetative control with interrupted dark periods. Induced plants transferred to continuous light showed further changes in the rates of cell division. The cell cycle was shortened more in the central zone than in the peripheral zone,i.e. there was a further shift in growth relations within the apical dome. The cell cycle in the leaf and bud primordia was also shortened if compared with the vegetative control, the acceleration being stronger in the bud primordia. There was a subsequent retardation in cell division in the leaf primordia formed during and after the inductive treatment if the plants were fully induced. An inhibition of the oldest bud primordia was observed in fully induced apices, as well.