Changes in the concentrations and transcripts for gibberellins and other hormones in a growing leaf and roots of wheat seedlings in response to water restriction

Background Bread wheat (Triticum aestivum) is a major source of nutrition globally, but yields can be seriously compromised by water limitation. Redistribution of growth between shoots and roots is a common response to drought, promoting plant survival, but reducing yield. Gibberellins (GAs) are necessary for shoot and root elongation, but roots maintain growth at lower GA concentrations compared with shoots, making GA a suitable hormone for mediating this growth redistribution. In this study, the effect of progressive drought on GA content was determined in the base of the 4th leaf and root tips of wheat seedlings, containing the growing regions, as well as in the remaining leaf and root tissues. In addition, the contents of other selected hormones known to be involved in stress responses were determined. Transcriptome analysis was performed on equivalent tissues and drought-associated differential expression was determined for hormone-related genes. Results After 5 days of applying progressive drought to 10-day old seedlings, the length of leaf 4 was reduced by 31% compared with watered seedlings and this was associated with significant decreases in the concentrations of bioactive GA(1) and GA(4) in the leaf base, as well as of their catabolites and precursors. Root length was unaffected by drought, while GA concentrations were slightly, but significantly higher in the tips of droughted roots compared with watered plants. Transcripts for the GA-inactivating gene TaGA2ox4 were elevated in the droughted leaf, while those for several GA-biosynthesis genes were reduced by drought, but mainly in the non-growing region. In response to drought the concentrations of abscisic acid, cis-zeatin and its riboside increased in all tissues, indole-acetic acid was unchanged, while trans-zeatin and riboside, jasmonate and salicylic acid concentrations were reduced. Conclusions Reduced leaf elongation and maintained root growth in wheat seedlings subjected to progressive drought were associated with attenuated and increased GA content, respectively, in the growing regions. Despite increased TaGA2ox4 expression, lower GA levels in the leaf base of droughted plants were due to reduced biosynthesis rather than increased catabolism. In contrast to GA, the other hormones analysed responded to drought similarly in the leaf and roots, indicating organ-specific differential regulation of GA metabolism in response to drought

The HB40-JUB1 transcriptional regulatory network controls gibberellin homeostasisin Arabidopsis

The phytohormones gibberellins (GAs) play fundamental roles in almost every aspect of plant growth and development. Although there is good knowledge about GA biosynthetic and signaling pathways, factors contributing to the mechanisms homeostatically controlling GA levels remain largely unclear. Here, we demonstrate that homeobox transcription factor HB40 of the HD-Zip family in Arabidopsis thaliana regulates GA content at two additive control levels. We show that HB40 expression is induced by GA and in turn reduces the levels of endogenous bioactive GAs by a simultaneous reduction of GA biosynthesis and increased GA deactivation. Hence, HB40 overexpression leads to typical GA-deficiency traits, such as small rosettes, reduced plant height, delayed flowering, and male sterility. In contrast, a loss-of-function hb40 mutation enhances GA-controlled growth. Genome-wide RNA-sequencing combined with molecular-genetic analyses revealed that HB40 directly activates transcription of JUNGBRUNNEN1 (JUB1), a key TF repressing growth by suppressing GA biosynthesis and signaling. HB40 also activates genes encoding GA 2-oxidases (GA2oxs) which are major GA catabolic enzymes. The effect of HB40 is ultimately mediated through induction of nuclear growth-repressing DELLA proteins. Our results thus uncover an important role of the HB40/JUB1/GA2ox/DELLA regulatory network in controlling GA homeostasis during plant growth.Plant science

Wpływ ładunków fosforu na strukturę makrofitów i status troficzny zbiornika zaporowego na małej rzece nizinnej

The main objective of the study was to evaluate if macrophytes structure and trophic status of dam reservoir Kraśnik on a small lowland river Wyżnica are determined by phosphorous loadings. Studies were conducted seasonally in May, July and October during the years 2008-2009. Samples were taken at four sites: Site 1 - inflow of the Wyżnica River to pre-dam, Site 2 − pre-dam, Site 3 − dam reservoir and Site 4 - outflow of the Wyżnica River from dam reservoir. Physical and chemical parameters (temperature, Secchi disc depth, dissolved oxygen, pH, conductivity, total suspension, chlorophyll-a, TP and P-PO4) were measured in water samples. Together with water parameters there were estimated biomass of phytoplankton and species composition and biomass of emergent, floating-leaved and submerged macrophytes. Concentrations of TP, chlorophyll-a and Secchi disc depth were used to calculate trophic state index of Carlsson for dam reservoir and its pre-dam. Based on mean water current, mean residence time of water in dam reservoir and concentrations of TP and P-PO4 loadings (g m-2) flowing into dam reservoir with the Wyżnica River were calculated. The results showed visible negative effect of phosphorous loadings on both macrophytes composition and trophic state of the reservoir. The marked changes concerned soft vegetation. High P loadings (7.74 g m-2 of TP and 6.03 g m-2 P-PO4) during the spring of 2008 caused the disappearance of characeans meadows. In 2009, the presence of rigid hornwort (Ceratophyllum demersum L.), the species typical for eutrophic lakes was noted. This unrooted submerged plant uptakes dissolved orthophosphates directly from the water column. Values of Carlsson index (51.4 ≤ TSI ≤ 68.2) indicate the eutrophic state of dam reservoir Kraśnik. During summer season in dam reservoir there were observed algal blooms (biomass of phytoplankton exceed 10 mg WW dm-3) and low water transparency (Secchi disc depth ranged from 0.4 to 0.65 m). During the two-year studies in dam reservoir Kraśnik a high reduction of P loadings, mostly dissolved orthophosphates was observed. Dependently on season, reduction of P-PO4 loadings ranged from 52% (July 2008) up to 91% (May 2009). The reduction of TP was lower and reached values from 15% (May 2008) to 48% (July 2009).Celem badań była ocena czy ładunki fosforu dopływające z wodami rzeki Wyżnicy mogą mieć istotny wpływ na strukturę makrofi tów i status trofi czny zbiornika zaporowego w Kraśniku. Badania prowadzono w trzech sezonach, maj, lipiec i październik w latach 2008-2009. Próby pobierano na czterech stanowiskach; stanowisko 1 - wpływ rzeki Wyżnicy do zbiornika wstępnego; stanowisko 2 - zbiornik wstępny; stanowisko 3 - zbiornik zaporowy; stanowisko 4 - odpływ rzeki Wyżnicy ze zbiornika zaporowego. W wodzie oznaczano parametry fi zyczne i chemiczne (temperatura, widzialność krążka Secchiego, tlen rozpuszczony, pH, przewodnictwo, zawiesina ogólna, chlorofi l-a, fosfor ogólny, fosfor fosforanowy). Ponadto analizowano biomasę fi toplanktonu oraz skład gatunkowy i biomasę makrofi tów wynurzonych, zanurzonych i o liściach pływających. Na podstawie stężenia fosforu ogólnego, chlorofi lu-a oraz widzialności krążka Secchiego obliczono wskaźnik trofi i Carlssona (TSI) dla zbiorników zaporowego i wstępnego. Na podstawie średnich przepływów, czasu retencji wody w zbiorniku oraz stężeń fosforu ogólnego i fosforanowego obliczono ładunki (g m-2), które dopływają do zbiornika z wodami rzeki Wyżnicy. Uzyskane wyniki wskazują, że ładunki fosforu dopływające do zbiornika zaporowego oddziałują negatywnie zarówno na strukturę roślinności zbiornika, jak i jego stan trofi czny. Najbardziej widoczne zmiany dotyczą składu gatunkowego roślinności miękkiej. W 2008 roku na skutek wysokich ładunków fosforu, zwłaszcza fosforanowego (6.03 g P-PO4 m-2), ze zbiornika ustąpiły ramienice. W 2009 roku odnotowano występowanie rogatka sztywnego, gatunku typowego dla wód żyznych, posiadającego zdolności wiązania fosforu fosforanowego bezpośrednio z toni wodnej. Wartości wskaźnika Carlssona (51.4 ≤ TSI ≤ 68.2), wskazują na eutrofi czny charakter wód zbiornika Kraśnik. W sezonie letnim zbiornik charakteryzuje się zakwitami glonów (biomasa fi toplanktonu przekracza wówczas 10 mg MM dm-3) oraz małą przezroczystością wody (widzialność krążka Secchiego waha się w granicach 0.4-0.65 m). W zbiorniku zaporowym Kraśnik następuje znaczna redukcja ładunków fosforu, przede wszystkim fosforanowego. W zależności od sezonu, redukcja fosforanowego wahała się w przedziale od 52% (lipiec 2008) aż do 91% (maj 2009). Redukcja ładunku fosforu ogólnego była znacznie niższa, osiągała wartości od 15% (maj 2008) do 48% (lipiec 2009)

Fabrics aramide inserts as the effective protection against 9 mm para FMJ pistol bullets according to the modified Iwlijew model

W artykule została podjęta próba matematycznego opisu zjawiska uderzenia pocisku 9 mm PARA FMJ w aramidowe ochrony balistyczne. W rozważaniach wykorzystano model Iwlijewa wprowadzając niewielkie jego modyfikacje. Analiza była prowadzona w oparciu o podstawowe prawa mechaniki klasycznej.An attempt of the mathematical description of the hitting phenomena of the 9 mm PARA FMJ round into the aramide ballistic protection is presented in the paper. The Iwlijew's model is used with small modifications and the analysis is based on classical mechanics laws

Development of stomata in Hordeum vulgare L. under the influence of oleander glycosides and colchicine

The effect of aqueous solutions of a 0.1 per cent mixture of oleander glycosides and of 0.1 and 0.5 per cent colchicine on the growth of seedlings, and particularly on the development of stomata was investigated in Hordeum vulgare L. The compounds were found not to penetrate with the same readiness through the coleoptile: glycosides passed very slowly, while colchicine rapidly. Growth inhibition of seedlings increased with the concentrations of the solutions applied, the time of incubation and the degree of damage to the coleoptile. Colchicine and glycosides cause a similar type of disturbances in all cell divisions leading to the formation of stomata. Most numerous disturbances were noted in phase II. The cause of these disorders lies in damage to the karyokinetic sipindle and abnormal cytokinesis. As a result are formed the stomata with a changed number of guard cells or subsidiary cells, their shape is changed and sometimes also their orientation and the dimensions are reduced