Urban salt contamination impact on tree health and the prevalence of fungi agent in cities of the central Lithuania

An analysis of tree health in urban greeneries exposed to winter road salt contamination was carried out in the cities of Alytus and Kaunas, Lithuania, during spring and summer 2009–2014. Trees were assessed for crown dieback, crown defoliation and foliage discolouration. In addition, the prevalence of saprotrophic pathogenic fungi that cause sooty mold disease was assessed in street and recreational plantings. Tilia cordata Mill. (small-leaved lime) was found to be the most common tree species among urban deciduous trees. Summarising the tree foliage results, saprotrophic fungi were detected on 16 species plants belonging to 13 genera. Three species of fungal pathogens belonging to two genera, two families, two classes, and two divisions, and 12 species of anamorphic fungi from nine genera were isolated and identified from Tilia cordata leaves. The most frequent sooty mold disease agents were Aspergillus brasiliensis and Cladosporium herbarum. Nonetheless, a weak correlation between salt contamination and lime tree damage by sooty mold was found.     

西瓜幼苗抗氧化系统对淹水胁迫的响应

为了研究西瓜植株在淹水情况下对淹水胁迫的响应,以蜜枚(M2x)和京牟(JM2x)2个二倍体西瓜品种为试材,在盆栽条件下研究了淹水胁迫对西瓜叶片受害指数、生理生化特性的影响。结果表明,西瓜幼苗在淹水胁迫下,真叶发黄失绿,随着淹水时间延长,茎开始腐烂,出现气生根,30d后淹水解除,植株生长无法恢复。西瓜幼苗叶片SOD活性在淹水初期下降,随着西瓜幼苗对淹水胁迫的适应,SOD开始回升,在胁迫8d后超出对照。淹水胁迫后西瓜幼苗叶片POD活性一直是上升趋势且高于对照。可溶性蛋白质含量受涝害后都比对照降低。随着淹水胁迫增加,PRO降低幅度加大。MDA含量受淹水胁迫后都比对照上升,MDA含量先降,后升高,再降低,然后大幅度升高。根据试验结果推断西瓜叶片伤害顺序为,SOD活性受抑制→活性氧增生→SOD、POD活性、PRO含量增加→清除活性氧→淹水胁迫加深→活性氧再增加→MDA积累→保护酶活性降低→质膜受损。京牟西瓜品种的耐淹水能力强于蜜枚。     

Effects of cerium on the antioxidant defence system in the petals and the contents of pigments in the calyces of Rosa chinensis Jacq. cut flower

To study the role of cerium (Ce) in regulating the vase life of Rosa chinensis Jacq. cut flowers, the effects of cerium nitrate (Ce(NO₃)₃) on the activities of antioxidant enzymes, the contents of malondialdehyde (MDA) and hydrogen peroxide (H₂O₂) in the petals, and the contents of chlorophyll a, chlorophyll b and carotenoids in the calyces were investigated. The results showed that Ce(NO₃)₃ evidently enhanced the activities of peroxidase (POD), catalase (CAT), superoxide dismutase (SOD), ascorbate peroxidase (APX), glutathione reductase (GR), glutathione S-transferase (GST) and glutathione peroxidase (GPX), and evidently decreased the contents of MDA and H₂O₂ in the petals, compared with the control. Moreover, Ce(NO₃)₃ evidently increased the contents of chlorophyll a, chlorophyll b and carotenoids in the calyces. The results also showed that Ce(NO₃)₃ evidently increased the numbers of open flowers and decreased the numbers of wilted flowers. Our results suggest that Ce(NO₃)₃ extended the vase life of R. chinensis Jacq. cut flower by improving the antioxidant defence system in the petals and the contents of pigments in the calyces.