engleski

Chloroplast ultrastructure, chlorophyll levels and photosystem II efficiency in horseradish (Armoracia lapathifolia Gilib.) tissue culture

In vitro grown horseradish (Armoracia lapathifolia Gilib.) plantlets, tumour and teratoma tissues were compared with regard to chloroplast ultrastructure, chlorophyll level and efficiency of photosystem II (PSII). Crown-gall tumours were induced on the leaf fragments with a wild octopine strain B6S3 of A. tumefaciens. From the same primary crown-gall tumour two tissue lines were established: unorganised tumour without any morphogenic capacity (TN) and teratoma composed of malformed shoots (TMsh) and unorganised tissue (TMn). For electron microscopy tissue was fixed with glutaraldehyde, postfixed with OsO4, dehydrated and embedded in Spurr's resin. Ultrathin sections were stained with uranyl acetate and lead citrate. Photosynthetic pigments were extracted with acetone and quantified spectrophotometrically. The maximum PSII efficiency was measured in dark-adapted samples. Relative electron transport rate (rel. ETR), photochemical (qP) and nonphotochemical quenching (qN) were investigated under low and high light conditions (30 and 100 μ mol photons/m2 s) by measurements of chlorophyll a fluorescence. In comparison to organised tissues (leaf and TMsh), unorganised tissues (TMn and TN) had lower content of total chlorophyll pigments, less developed thylakoid system, dysfunctional PSII and significantly lower rel. ETR and qP at both irradiance levels. On the contrary, qN values were higher at both light levels for unorganised tissues. In the leaf and TMsh rel. ETR was significantly different at both irradiance levels but qP values were not. The obtained results showed that cell transformation and tissue developmental stage influence chloroplast ultrastructure, chlorophyll level and photosystem II efficiency.

horseradish; chloroplast ultrastructure; chlorophyll levels; PSII efficiency

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