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Responses to UV-B exposure by saplings of the relict species Davidia involucrata Bill are modified by soil nitrogen availability

Li Y., Gao J., Zhang L., Su Z.

Polish Journal of Ecology

2014

Vol. 62, nr 1

101--110

Climate change scenarios suggest that plants will be exposed to increasing levels of ultraviolet radiation in the future. The dove tree, Davidia involucrata Bill (Davidiaceae) is a rare and endangered tree species in China. Its distribution is predicted to become more montane as the climate warms, exposing it to higher levels of UV-B and different soil conditions. We compared the effects of glasshouse ambient (7.08 uW cm-2) and increased (13.93 uW cm-2) UV-B on survivorship, secondary metabolites indicative of radiation damage, and putative defensive responses of Davidia involucrata saplings growing under current and increased nitrogen conditions (5 and 25 g m-2 a-1 N). Mortalities were higher among plants exposed to increased UV-B, but only in soils with high supplementary nitrogen. Increases in compounds associated with defense against radiation were more frequently recorded under high supplementary nitrogen conditions. This rare and localised plant is highly sensitive to elevated UV-B when growing in high nitrogen soils, a combination that is likely to increase in the summer.

Free proline content in leaves of Salix viminalis as an indicator of their resistance to substrate salinity

Stolarska A., Wróbel J., Przybulewska K.

Ecological Chemistry and Engineering. A

2008

Vol. 15, nr 1-2

139-146

In the own research, an attempt was undertaken to evaluate resistance of three basket willow clones - Bjor, Jorr and Tora - to the stress induced by substrate salinity and to determine the content of free amino acid, ie of proline, in leaves as a sensitive bioindicator in differentiation of stress agent intensity as well as to measure selected physiological indices. Hydroponic experiment was carried out in 2004-2005. In this two-factor experiment, the first factor was three basket willow clones, Bjor, Jorr and Tora, whereas tour levels of substrate salinity: 0.00 (control), 0.034,0.068 and 0.102 mol. dm-3, represented the second factor. During the vegetation period, the intensity of gaseous exchange, ie E-transpiration (mmol m-2 . s-1) and A-assimUation of CO2 ([mu]mol m-2 s-1), as well as water saturation deficit in leaves (WSD) were measured. Basing on the results of gaseous exchange, water consumption efficiency in photosynthesis WF [mmol mol-1] was calculated. In the plant material (leaves), proline content [mg g-1 d.m.] was determined 7 days after salination of substrate with the method of Bates et al. (1973), as well as sodium and potassium contents [mg kg-1] with AAS method and their quantitative proportions (K/Na ratio) and fresh and dry matters [g]. As a result of the conducted experiment, significant differences were found in the content of free proline in the leaves of examined clones and between the levels of solution salinity. The leaves of Tora clone were characterized by significantly smaller concentration of free proline than those of Bjor and Jorr clones. While referring to salinity level, proline was accumulated by willow leaves most when substrate salinity was the largest; there was over two times more proline in Bjor and Jorr clones than under control conditions. The synthesis of that amino acid also significantly depended on the content of Na+ and K+ ions in leaves, but differently. In Bjor i Jorr clones, it rose together with the increase in the number of Na+ ions, whereas together with the increase of K+ ions in Tora clone. In Bjor clone, significant negative relationships were also found between the content of that amino acid and the volume of fresh and dry matter in the over ground part of basket willow and positive relations between proline and (WSD).

W badaniach własnych podjęto próbę oceny odporności trzech klonów wierzby wiciowej: Bjor, Jorr i Tora na stres wywołany zasoleniem pożywki (0.0; 0.034; 0.068; 0.1 02 mol, dm-3) oraz oznaczenie zawartości wolnego aminokwasu, tj. proliny w liściach jako czułego bioindykatora w różnicowaniu natężenia czynnika stresowego, a także pomiary wybranych wskaźników fizjologicznych. Dwuczynnikowe doświadczenie hydroponiczne przeprowadzono w latach 2004-2005. W czasie wegetacji mierzono intensywność wymiany gazowej, tj. E-transpiracji (mmol m-2. s-1) i A-asymilacji CO2 ([mu]mol m-z.2 s-1) oraz deficyt wysycenia liści wodą (WSD). Z wyników wymiany gazowej obliczono WF - fektywność wykorzystania wody w fotosyntezie [mmol mol-1]. W materiale roślinnym (liście), 7 dni po zasoleniu pożywki oznaczono zawartość proliny metodą Batesa i wspł. (1973) w [mg g-1 s.m.], a także zawartość sodu i potasu [mg kg-1] (metodą MS) i ich ilościowe proporcje (K/Na) oraz świeżą i suchą masę [g]. W wyniku przeprowadzonego eksperymentu stwierdzono statystycznie istotne różnice w zawartości wolnej proliny w liściach badanych klonów oraz między poziomami zasolenia roztworów. Liście klonu TORA charakteryzowały się mniejszą koncentracją wolnej proliny niż liście klonów BJOR i JORR, najwięcej proliny zgromadziły liście wierzby w warunkach największego zasolenia pożywki, u Bjor i Jorr było ponad dwukrotnie więcej proliny niż w warunkach kontrolnych. Synteza proliny zależała od zawartości jonów Na+ i K+ w liściach, ale nie jednakowo, u Bjor i Jorr rosła wraz ze wzrostem ilości jonów Na" a u Tora wraz ze wzrostem jonów K+. U klonu Bjor wykazano również ujemnie zależność pomiędzy zawartością aminokwasu a ilością świeżej i suchej masy części nadziemnej oraz dodatnią ze wskaźnikiem WSD.