Aynur Gürel

Effect of water deficit and potassium fertilization on photosynthetic activity in cotton plants

Abstract Physiological mechanisms that can contribute to drought tolerance and the role of potassium fertilization in cotton were studied by evaluation of parameters describing photosynthetic performance. Gas-exchange and chlorophyll fluorescence characteristics were measured on leaves of two cotton genotypes, one drought sensitive (Nazilli 84-S) and the other drought tolerant (Sahin 2000), grown in field conditions in the Aegean region of Turkey under different regimes of water and potassium supply. It was shown that under drought conditions without potassium fertilization Sahin 2000 had a higher photosynthetic rate and stomatal conductance than Nazilli 84-S. Potassium fertilization to a great extent compensated for the inhibitory effect of drought on photosynthesis. Application of the JIP test by using chlorophyll fluorescence data revealed that the drought sensitive Nazilli 84-S was more responsive to potassium fertilization than Sahin 2000, as judged by a number of parameters representing quantum efficiency of the processes and energy fluxes in photosystem (PS) II. The observed decrease in photosynthetic CO2 assimilation in both cotton cultivars under drought conditions was not accompanied by any significant decrease in the electron transport flux in PSII and maximum quantum yield of primary photochemistry.

Induction of Gentiana cruciata hairy roots and their secondary metabolites

Gentiana cruciata L. (cross gentian) is a medicinal and ornamental plant. The root extracts of this species are known to exhibit many curative properties. The natural Gentiana populations are exposed to great danger because of their uncontrolled usage. In this study, hairy roots from Gentiana cruciata L. stem and leaf explants belonging to three different clones were induced by inoculation with four different Agrobacterium rhizogenes wild strains namely A4, 15834, 8196 and R1000. Induction of the root transformation was significantly dependent on the explant type used. On the other hand, the genotype and bacterial strain had no significant effect on hairy root formation. Hairy root formation percentages of the explants varied between 5.6–33.3% in the stem explants, and between 0.0–6.7% in the leaf explants. Transformations of the hairy roots were confirmed by PCR using rolC specific primers, and revealed the absence of contaminating A. rhizogenes with virC primers. Total of twelve hairy root clones were obtained, and their secondary metabolite content was also analyzed by HPLC. Quantitative results exhibited that gentiopicroside was the most abundant compound in all root samples. Furthermore, metabolites such as loganic acid, swertiamarin, and sweroside were also identified and quantified in the samples.

Reddening of Cotton (Gossypium Hirsutum L.) Leaves

Reddening of leaves is a physiological disorder in cotton induced by different abiotic stresses. Dramatic biochemical changes occurred in reddening leaves: strong accumulation of anthocyanins and drop of chlorophyll content, important increase of proline content and peroxidase activity. The lipid peroxide content indicative of membrane fragmentation was decreased. In this way a multicomponent system encompassing anthocyanins, proline, and peroxidase may act coordinately to overcome abiotic stress in cotton.

Effects of Reddening of Cotton (Gossypium hirsutum L.) Leaves on Functional Activity of Photosynthetic Apparatus

Strong inhibition of rates of CO2 assimilation and transpiration, stomatal conductance, and water use efficiency as well as photosystem 2 (PS2) photochemical activity were related to the severity of reddening. The inhibition of photosynthesis in red cotton leaves was due to both decreased photochemical activity and stomatal limitation. Lowered photosynthetic capacity could be one of the main factors of reduced yield in reddening cotton.

Direct plant regeneration from different explants through micropropagation and determination of secondary metabolites in the critically endangered endemic Rhaponticoides mykalea

Direct plant regeneration from different explants, micropropagation and determination of secondary metabolites were studied in the critically endangered endemic Rhaponticoides mykalea (Hub.-Mor.) M.V. Agab & Greuter. Seed germination was achieved by damaging the seed coat and cultivating the embryos on Woody Plant Medium (WPM), of which 40% germinated. The epicotyls and cotyledonary petioles of seedlings were used as initial explants and direct shoot regeneration was obtained on WPM containing 2.22 μM 6-benzyladenine (BA). WPM medium supplemented with 2.22 μM BA and 4.92 μM indole-3-butyric acid (IBA) significantly improved the production of multiple shoots, resulting in an average of 5.6 shoots per explants. The highest rooting of shoots (35.6%) was observed with WPM medium containing 19.68 μM IBA with 990 μM putrescine. Plantlets with well-developed roots were transferred to soil and acclimatised within a plant growth chamber. Acclimatised plants showed 100% survival rate and remained healthy. As a part of our study, the content of secondary metabolites in three tissue culture regenerated lines were determined by HPLC analysis. Chlorogenic acid, Quercetin and scutellarin were confirmed secondary metabolites of R. mykalea.

Rubia tinctorum L. Hücre Kültürlerinde Tuz Stresi ve Inokülasyon Oranlarının Etkileri

Bu calismada, Rubia tinctorum L. callus ve hucre suspansiyon kulturlerine 100 mM ve 200 mM konsantrasyonlarda tuz stresi uygulanarak elde edilen biyokutlelerdeki yas ve kuru agirliklar (g), bagil kuru agirlik oranlari (mg/g kuru agirlik) ve alizarin ve purpurin icerikleri uzerine etkileri belirlenmistir. Tuz consantrasyonundaki artisa bagli olarak, callus ve hucre suspansiyon kulturlerinden elde edilen biyokutle azalmistir. Kallus kulturlerindeki hucrelerde dusuk canlilik ve cogalma oranina ragmen, biyokutle belirgin bir dusus gostermemistir. Kallus kulturlerinde tuz konsantrasyonu arttikca alizarin ve purpurin icerigi azalmistir, ancak bu bilesiklerin miktari hucre suspansiyon kulturlerinde artmistir. Yapilan denemelerde inokulasyon oranlarinin yas ve kuru agirlik miktari ve alizarin ve purpurin icerigi uzerine etkili oldugu tespit edilmistir. Hucre suspansiyon kulturlerinde 1:2 inokulasyon orani daha yuksek alizarin ve purpurin icerigi saglarken, 1:4 inokusyon oraninda biyokutle miktari daha fazladir. En yuksek alizarin ( 3.183 mg/g) ve purpurin ( 1.153 mg/g) icerikleri 1:2 inokulasyon oraninda ve 200 mM NaCl iceren besin ortamindan tespit edilmistir.

Effect of reddening of cotton (Gossypium hirsutum L.) leaves on the ultrastructure of mesophyll cells

The ultrastructure of cotton leaves, exhibiting reddening as symptom of physiological disorder, was examined by means of transmission electron microscopy. Osmiophilisation of the membrane compartment was established. Massive agglomerations on the tonoplast in the vacuole of cells under the adaxial epidermis were observed, and were referred to as electron-dense osmiophilic substance, most probably of anthocyanin nature. In chloroplast stroma a zone of low electron density enclosing numerous osmiophilic aggregations of unclear chemical character was differentiated. Fragmentation and severe destruction of thylakoids in chloroplasts of reddening cotton leaves was not detected.