Mechanizmy rezistencie k suchu v rastlinách špenátu (Spinacia oleracea L.) a štvorbôčiku rozložitého (Tetragonia expansa Murr.) počas dehydratácie pôdy

Abstract

In the pot experiments with commercial genotypes of common spinach (Spinacia oleracea L.) and New Zealand spinach (Tetragonia tetragonoides (Pall.) Kuntze) genotypic differences were studied in the capacity for osmotic adjustment occurred under progressive drought. The degree of plant drought tolerance was characterized through quantification of stomatal conductance, free proline and pigment contents. Water stress negatively affected the water regime of plants of all studied genotypes. Under the well-hydrated conditions, a non-significant genotypic difference was observed in the relative water content (RWC) (P=0.545) and osmotic potential (ψS) (P=0.637), respectively. The significant genotypic differences were observed in stomatal conductance (P<0.001). In the terminal phase of dehydration cycle, the statistically significant genotype differences (P<0.01) in RWC and ψS, as well as in the capacity for osmotic adjustment (P=0.032) was recorded. Moreover, a significant correlation between the osmotic adjustment and concentration of proline was measured in all genotypes (rP=0.74, P=0.009). The results showed that proline is an important osmolyte in spinach during the progressive dehydration. It was also observed that the stomata of New Zealand spinach were very sensitive to dehydration. The concentration of chlorophyll pigments, especially Chl b, decreased and Chl a/ Chl b ratio increased under dehydration in all genotypes. Finally, drought resistance of spinach genotypes (especially 'Neptun') can be characterized by the mechanism of dehydration tolerance and plants of New Zealand spinach by the mechanism of dehydration avoidance.