To better understand the long-term impact of Ophiostoma novo-ulmi Brasier on leaf physiology in 'Dodoens', a Dutch elm disease-tolerant hybrid, measurements of leaf area, leaf dry mass, petiole anatomy, petiole hydraulic conductivity, leaf and branch water potential, and branch sap flow were performed 3 years following an initial artificial inoculation. Although fungal hyphae were detected in fully expanded leaves, neither anatomical nor morphological traits were affected, indicating that there was no impact from the fungal hyphae on the leaves during leaf expansion. In contrast, however, infected trees showed both a lower transpiration rate of branches and a lower sap flow density. The long-term persistence of fungal hyphae inside vessels decreased the xylem hydraulic conductivity, but stomatal regulation of transpiration appeared to be unaffected as the leaf water potential in both infected and non-infected trees was similarly driven by the transpirational demands. Regardless of the fungal infection, leaves with a higher leaf mass per area ratio tended to have a higher leaf area-specific conductivity. Smaller leaves had an increased number of conduits with smaller diameters and thicker cell walls. Such a pattern could increase tolerance towards hydraulic dysfunction. Measurements of water potential and theoretical xylem conductivity revealed that petiole anatomy could predict the maximal transpiration rate. Three years following fungal inoculation, phenotypic expressions for the majority of the examined traits revealed a constitutive nature for their possible role in Dutch elm disease tolerance of 'Dodoens' trees.

• MeSH
• analýza hlavních komponent MeSH
• časové faktory MeSH
• hybridizace genetická MeSH
• kvantitativní znak dědičný * MeSH
• listy rostlin mikrobiologie   fyziologie   MeSH
• nemoci rostlin mikrobiologie   MeSH
• Ophiostoma fyziologie   MeSH
• stonky rostlin mikrobiologie   fyziologie   MeSH
• transpirace rostlin fyziologie   MeSH
• Ulmus mikrobiologie   fyziologie   MeSH
• voda MeSH
• xylém mikrobiologie   MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH

Spring drought is becoming a frequently occurring stress factor in temperate forests. However, the understanding of tree resistance and resilience to the spring drought remains insufficient. In this study, European beech (Fagus sylvatica L.) seedlings at the early stage of leaf development were moderately and severely drought stressed for 1 month and then subjected to a 2-week recovery period after rewatering. The study aimed to disentangle the complex relationships between leaf gas exchange, vascular anatomy, tree morphology and patterns of biomass allocation. Stomatal conductance decreased by 80 and 85% upon moderate and severe drought stress, respectively, which brought about a decline in net photosynthesis. However, drought did not affect the indices of slow chlorophyll fluorescence, indicating no permanent damage to the light part of the photosynthetic apparatus. Stem hydraulic conductivity decreased by more than 92% at both drought levels. Consequently, the cambial activity of stressed seedlings declined, which led to lower stem biomass, reduced tree ring width and a lower number of vessels in the current tree ring, these latter also with smaller dimensions. In contrast, the petiole structure was not affected, but at the cost of reduced leaf biomass. Root biomass was reduced only by severe drought. After rewatering, the recovery of gas exchange and regrowth of the current tree ring were observed, all delayed by several days and by lower magnitudes in severely stressed seedlings. The reduced stem hydraulic conductivity inhibited the recovery of gas exchange, but xylem function started to recover by regrowth and refilling of embolized vessels. Despite the damage to conductive xylem, no mortality occurred. These results suggest the low resistance but high resilience of European beech to spring drought. Nevertheless, beech resilience could be weakened if the period between drought events is short, as the recovery of severely stressed seedlings took longer than 14 days.

• MeSH
• buk (rod) * MeSH
• fotosyntéza MeSH
• listy rostlin MeSH
• období sucha * MeSH
• semenáček MeSH
• voda MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH

Marine phytomyxids represent often overlooked obligate biotrophic parasites colonizing diatoms, brown algae, and seagrasses. An illustrative example of their enigmatic nature is the phytomyxid infecting the seagrass Halophila stipulacea (a well-known Lessepsian migrant from the Indo-Pacific to the Mediterranean Sea). In the Mediterranean, the occurrence of this phytomyxid was first described in 1995 in the Strait of Messina (southern Italy) and the second time in 2017 in the Aegean coast of Turkey. Here we investigated, using scuba diving, stereomicroscopy, light and scanning electron microscopy, and molecular methods, whether the symbiosis is still present in southern Italy, its distribution in this region and its relation to the previous reports. From the total of 16 localities investigated, the symbiosis has only been found at one site. A seasonal pattern was observed with exceptionally high abundance (> 40% of the leaf petioles colonized) in September 2017, absence of the symbiosis in May/June 2018, and then again high infection rates (~ 30%) in September 2018. In terms of anatomy and morphology as well as resting spore dimensions and arrangement, the symbiosis seems to be identical to the preceding observations in the Mediterranean. According to the phylogenetic analyses of the 18S rRNA gene, the phytomyxid represents the first characterized member of the environmental clade "TAGIRI-5". Our results provide new clues about its on-site ecology (incl. possible dispersal mechanisms), hint that it is rare but established in the Mediterranean, and encourage further research into its distribution, ecophysiology, and taxonomy.

• MeSH
• Cercozoa klasifikace   genetika   fyziologie   MeSH
• fylogeneze MeSH
• Hydrocharitaceae parazitologie   MeSH
• listy rostlin parazitologie   MeSH
• RNA protozoální analýza   MeSH
• RNA ribozomální 18S analýza   MeSH
• symbióza * MeSH
• zavlečené druhy MeSH
• Publikační typ
• časopisecké články MeSH
• Geografické názvy
• Itálie MeSH
• Středozemní moře MeSH