Issues regarding the chloroplast ultrastructure and assimilating pigments content in normal and hyperhydrice sugar beet (Beta vulgaris L. var. Saccharifera) vitroplantlet leaflets

Authors: Dorina CACHIŢĂ-COSMA¹, Adriana PETRUŞ-VANCEA²*, Constantin CRĂCIUN³

Affiliatin: ¹ Faculty of Natural Science, “Vasile Goldiş” Western University, Arad, Romania; ² Biology Department, Faculty of Science, University of Oradea, Romania; ³ Electron Microscopy Centre, „Babeş-Bolyai” University, Cluj-Napoca, Romania

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ABSTRACT. Sugar beet plantlet leaflets aged 30 days, obtained from seeds germinated and grown in a greenhouse, or from vitroplantlets, were subjected to ultrastructural and biochemical analysis. In terms of cytology, the foliar mesophyll cells from in vitro cultivated plantlets had an increased chloroplasts number than assimilating parenchyma cells of vitroleaflets. More, the vitroplantlet chloroplasts were smaller, had a flatted form, granale and tylacoidale system was poorly represented, but their stroma was rich in starch. Hyperhydrice vitroplantlet leaflets were the most chloroplasts poorest. They were either fusiform or hypertrophies. In some cells they were in a disorganization process, and occasionally, they had not an integrity membrane. In such cells, the chloroplasts are scattered in the myxoplasma, which was formed after the tonoplast disintegration and the cytoplasm was mixed with vacuolar juice. Compared with sugar beet plantlet leaflets, grown in the greenhouse, the hyperhydrice vitroleaflets had 72% less chlorophyll a; in non-hyperhydrice vitroplantlets, the chlorophyll a from leaflets decreased with only 45%; the chlorophyll b content in hyperhydrice vitroplantlets decreased with 50 %, compared to similar parameter that was obtain in greenhouse plantlets; in contrast, at those non-hyperhydrice, the chlorophyll b decreased with only 29.6%. At sugar beet vitrocultivated plantlets, but those non-hyperhydrice, the total green pigments was decreased with 37.2%, compared to that marked in the leaves of plants grown in greenhouse for 30 days, while in hyperhydrice vitroplantlets, the values of this parameter were reduced with 63.3%. Opposite to the carotenoid pigments content recorded of sugar beet plantlets from greenhouse, to normal vitroleaflets the level has decreased with 7%; in contrast, to hyperhydrice vitroplantlets, this parameter decreased with 55%. The experiment has highlighted the profound transformation suffered by sugar beet hyperhydrice vitroplantlets, both in altering terms of the chloroplasts structure and in a fast decrease of the assimilating pigments contents, especially in chlorophyll a.

Keywords: chloroplast, ultrastructure, hyperhydricity, assimilating pigments