Response of barley seedlings to water deficit and enhanced UV-B irradiation acting alone and in combination

Abstract

Responses of barley seedlings to water deficit (WD) induced by polyethylene glycol (PEG 6000) and ultraviolet (UV-B; 280-320 nm) radiation and their interaction (UV-B ? WD) were examined. A decrease in dry matter yield and water content of leaves and roots was observed following application of WD and UV-B ? WD, while no changes were found after treating barley plants with UV-B. Proline content was increased in leaves under WD conditions and UV-B ? WD. In contrast, UV-B treatment had no effect on the accumulation of proline in leaves of barley plants. Changes in root proline content showed a varied response: WD induced an increase in the level of this amino acid, while UV-B as well as UV-B ? WD suppressed root proline content. The lipid peroxidation product malondialdehyde (MDA) was increased in leaves under WD and UV-B ? WD stresses. Root MDA content increased in WD-stressed plants, but it decreased in the case of combined application of both stresses. The applied stress factors operated in a variable manner on phenylpropanoid metabolism. Phenylalanine ammonialyase (PAL) activity in leaves and roots was stimulated after exposure to WD and application of UV-B ? WD stresses, while UV-B stress did not affect its activity. On the other hand, UV-B treatment enhanced the activity of 4:coumarate-CoA ligase (4CL) in leaves and this enhancement was positively correlated with the accumulation of anthocyanins and flavonols. However, the combined application of WD and UV-B reduced the positive effect of UV-B on the accumulation of these compounds and the activity of 4CL. Surprisingly, anthocyanins and flavonols were not detected in roots of examined barley seedlings despite increased 4CL activity. The results suggest that UV-B-induced activation of 4CL as well as accumulation of anthocyanin and flavonols in leaves is beneficial for the response to this stress factor. On the other hand, WD-induced reduction of the effect of UV-B on 4CL activity and the contents of anthocyanin and flavonol might be a cause of membrane damage in UV-B-and WDstressed plants. In addition, conversely to what could be expected, the UV-B effect was perceived by the waterstressed roots, which exhibited reduced lipid peroxidation (MDA) and proline accumulation in WD-stressed plants exposed to UV-B.

UV-B radiation increases anthocyanin levels in cotyledons and inhibits the growth of common buckwheat seedlings

“…These general principles were confirmed in our study which demonstrated that the concentrations of cyanidin-3-O-galactosyl-rhamnoside and cyanidin-3-O-glucosyl-rhamnoside in the cotyledons of all tested buckwheat cultivars increased significantly under exposure to UV-B radiation. Similar results were previously noted in common buckwheat [7,25,28], Tartary buckwheat [31] and other plants [2,19,21].…”

“…Their presence in the walls of epidermal cells is generally associated with UV protection, whereas the presence of mesophyll cells in vacuoles and chloroplasts is linked with reactive oxygen species scavenging [1]. According to many reports, UV-B radiation increases flavonoid levels in young plants [2,19,21,25]. In this study, the concentrations of individual flavones indicate that the effect of UV-B is genetically determined ( Table 2).…”

Seasonal variability of phenolic compounds and antioxidant activity in prickly pear cladodes of Opuntia and Nopalea genres

“…However, the availability of water increases the phenolic compounds in tomato cultivars (Barbagallo et al, 2008) and barley (Bandurska et al, 2012). The mechanisms that regulate this influence are not completely clear, and there is variability in responses between species and cultivars.…”

“…This variation was 29.4% (IPA-20) to 271.4% (F-21) (Figure 2). Generally the reduction in water addition increases the content of phenolic compounds and anthocyanins in plants, since these molecules act against water stress (Bandurska et al, 2012).…”

Exogenous adenosine 5′-phosphoramidate behaves as a signal molecule in plants; it augments metabolism of phenylpropanoids and salicylic acid in Arabidopsis thaliana seedlings

“…Degradation of cAMP and cGMP is catalyzed by more or less specific 3 0 ,5 0 -cyclic nucleotide phosphodiesterases (EC 3.1.4.17) (Pietrowska-Borek et al, 2014a). (4) Plant cells respond to stress by intensifying production of various phenylpropanoic compounds (Lawton et al, 1983;Dixon and Paiva, 1995;Liu and McClure, 1995), such as flavonoids (Winkel-Shirley, 2001;Olsen et al, 2008), lignins (Moura et al, 2010), anthocyanins (Steyn et al, 2002;Bandurska et al, 2012) and salicylic acid (Hayat Abbreviations: PAL, phenylalanine:ammonia lyase; 4CL, 4-coumarate:coenzyme A ligase; C4H, cinnamate-4-hydroxylase; CHS, chalcone synthase; CCR, cinnamoylcoenzyme A:NADP oxidoreductase; ICS, isochorismate synthase; NH 2 -pA, adenosine 5 0 -phosphoramidate; F-pA, adenosine 5 0 -monophosphofluoride; SA, salicylic acid; HIT proteins, superfamily of proteins that contain histidine-triad sequence motif. Bandurska and Cie slak, 2013).…”