Stefan Pietkiewicz

Degradation and Colonization of Cellulose by Diazotrophic Strains of Paenibacillus polymyxa Isolated from Soil

The bioconversion of cellulose to soluble sugars by diazotrophic bacteria is a very important for the environment, such as for the global stabilization and a sustainable human society. Two nitrogen-fixing microorganisms hydrolyzing cellulose were isolated from agricultural soil and identified as Paenibacillus polymyxa [the laboratory names EG2 and EG14] based on 16Sr RNA sequence. The genome of these bacteria was found to carry nif genes coding the individual components of the nitrogenase complex. Their nitrogen fixing ability was confirmed by studying nitrogenase activity in cultures of the studied bacteria in N-free medium supplemented with carboxymethylcellulose (CMC). The nitrogenase activity of P. polymyxa EG 2 was 2.9 nM C2H4∙ml-1∙h-1 whereas P. polymyxa EG 14 0.4nM C2H4∙ml-1∙h-1. The isolates in medium with filter paper synthesize following cellulolytic enzymes: carboxymethylcellulase (CMCase), FPase and Avicellase. Of the cellulolytic enzymes in the culture supernatants of the bacteria the most abundant was CMCase (P. polymyxa EG 2 103.4 mU, EG 14:96.1 mU) with far lower amounts of enzymes hydrolyzing crystalline Avicel cellulose or filter paper. In spite of these observations the better isolate in terms of synthesis of cellulases is P. polymyxa EG 14. Zymograms reflecting the main cellulase activities of the studied bacteria do not significantly differ from each other and present at least three major enzymatic activities with high molecular masses: one of about 200 kDa, another of about 220 kDa and a strong band of activity with mass of about 130 KDa. Observations of the bacterial cultures in medium with filter paper revealed the colonization of the substrate by single cells or aggregates of bacterial cells surrounded by slime. Scanning and transmission microscopy of the isolates revealed the presence of spherical structures resembling cellulosomes on the surface of the bacteria being characteristic for anaerobic bacteria of the genus Clostridium.

Photosynthetic efficiency and survival of Dactylis glomerata and Lolium perenne following low temperature stress

Resistance to low temperature is crucial for overwintering crops. In this work we compared the resistance to low temperature treatment of some varieties of two forage grass species Dactylis glomerata L. and Lolium perenne L. in order to elucidate the reason for the better resistance found in some species. The variety Amila of D. glomerata and Diament of L. perenne were more tolerant to low temperature stress during the emergence and tillering phases as compared to the varieties Amera and Gagat. The improved tolerance and ability for recovery after stress were associated with the better recovery of photosynthetic efficiency of these varieties and better survival of their shoots after low temperature stress.

Identification and differential expression of two dehydrin cDNAs during maturation of Jatropha curcas seeds

Plant dehydrin proteins (DHNs) are known to be important for environmental stress tolerance and are involved in various developmental processes. Two full-length cDNAs JcDHN-1 and JcDHN-2 encoding two dehydrins from Jatropha curcas seeds were identified and characterized. JcDHN-1 is 764 bp long and contains an open reading frame of 528 bp. The deduced JcDHN-1 protein has 175 a.a. residues that form a 19.3-kDa polypeptide with a predicted isoelectric point (pI) of 6.41. JcDHN-2 is 855 bp long and contains an open reading frame of 441 bp. The deduced JcDHN-2 protein has 156 a.a. residues that form a 17.1-kDa polypeptide with a predicted pI of 7.09. JcDHN-1 is classified as type Y3SK2 and JcDHN-2 is classified as type Y2SK2 according to the YSK shorthand for structural classification of dehydrins. Homology analysis indicates that both JcDHN-1 and JcDHN-2 share identity with DHNs of other plants. Analysis of the conserved domain revealed that JcDHN-2 has glycoside hydrolase GH20 super-family activity. Quantitative real time PCR analysis for JcDHN-1 and JcDHN-2 expression during seed development showed increasing gene expression of both their transcript levels along with the natural dehydration process during seed development. A sharp increase in JcDHN-2 transcript level occurred in response to water content dropping from 42% in mature seeds to 12% in dry seeds. These results indicate that both JcDHNs have the potential to play a role in cell protection during dehydration occurring naturally during jatropha orthodox seed development.

Effective microorganisms impact on photosynthetic activity of Arabidopsis plant grown under salinity stress conditions

Abstract Effective microorganisms impact on photosynthetic activity of Arabidopsis plant grown under salinity stress conditions. Salinity is one of the main abiotic stressors which affects plant growth through various physiological processes such as photosynthesis. The aim of this work is to study the impact of salinity stress on Arabidopsis plants by evaluating plant growth rate and photosynthetic activity, while investigating the influence of effective microorganisms (EMs) with the objective to determine if EMs could alleviate the induced stress affiliated with salinity. Results showed that salinity negatively affects photosynthesis efficiency in Arabidopsis plants based on the data obtained from the measured chlorophyll fluorescence parameters. Additionally, application of EMs enhanced plant tolerance to counteract the induced stress. Effective microorganisms concentration of 10 mL/L suggested to bring about the best results. This work advocates, that quantum efficiency of photosystem II (PSII) is a reliable indicator for tolerance in Arabidopsis plants to salinity stress, the impact of which may be softened by the EMs.

Canopy Architecture and Yielding of Different Tomato Morphotypes Under Glasshouse Conditions

Canopy Architecture and Yielding of Different Tomato Morphotypes Under Glasshouse Conditions Two tomato morphotypes (cvs. Favorita, Organza and Azarro) of different fruit size were grown during 2005-2006 on a rockwool substrate under greenhouse conditions. Leaf area index (LAI), solar radiation absorption coefficient (TAO) and leaf area duration (LAD) were determined. Tested tomato cultivars proved different yielding strategies expressed by dissimilar values of the measured and calculated physiological indices (LAI, LAD, TAO and the canopy yielding efficiency). Cv. Organza showed the highest canopy yielding efficiency, cv. Azarro showed a negative dependence between LAD and yield, while cv. Favorita canopy architecture allowed to achieve better penetration of light energy to lower canopy layers and showed better tolerance of this cultivar to thermal stress. Pokrój Roślin a Plonowanie Różnych Morfotypów Pomidora w Warunkach Szklarniowych W latach 2005-2006 uprawiano w warunkach szklarniowych na podłożu z wełny mineralnej dwa morfotypy pomidora (odm. Favorita, Organza i Azarro) o różnej wielkości owoców. Oznaczono wskaźnik powierzchni liści (LAI), współczynnik absorpcji promieniowania słonecznego (TAO) oraz wskaźnik długotrwałości powierzchni liści (LAD). Badane odmiany pomidora wykazały różne strategie plonowania wyrażone poprzez odmienne wartości pomierzonych i obliczonych wskaźników fizjologicznych (LAI, LAD, TAO i wydajność plonotwórczą łanu). Odm. Organza odznaczała się najwyższą wydajnością plonotwórczą, odm. Azarro wykazywała ujemną zależność pomiędzy LAD a plonem, natomiast architektura łanu odm. Favorita umożliwiała lepszą penetrację energii promieniowania do dolnych warstw listowia i wykazywała większą tolerancję u tej odmiany na stres termiczny.

Growth analysis of rape during the binding and formation of pods

Field experiment was conducted to analyze the growth dynamics of the oilseed rape and the filling of pods in two types (cv. Brendy population and cv. Primus F1 hybrid). The variant of quantitative growth analysis for a single plant was chosen. It was found that the hybrid variety has a higher tolerance to biotic stresses that may occur (pests and diseases) and periodic drought (increased water storage capacity). However, it created a lower dry weight and lost the leaves earlier. Population produces more dry matter, earlier it establishes a fixed proportion of each organ within, but is exposed on spill on the seeds. As a result, the difference in the yield of the seed was 0,4 t ha-1 in favor of the hybrid. Hybrid oilseed rape breeding should strive to early establish a rigid proportion of the various organs of the dry weight of the plant.