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Speci_c primers and dual!labelled~uorogenic probes were designed for polymerase chain reaction "PCR#! based detection of both\ mycorrhizal and pathogen DNA[ Based on the on!line connection with an auto! mated ABI Prism 6699 sequence detector\ amplicon quanti_cation was directly performed during the PCR[ The starting copy numbers of target sequences present in each reaction were calculated by comparing the Ct!values of unknown samples to the Ct!values of standards with known amounts of DNA[ The Ct!value depends on the input of starting copies and is de_ned as that cycle num! ber at which a statistically signi_cant increase in the reporter~uorescence can _rst be detected[ DNA was extracted from 00 as well as 099 spores of the mycorrhizal fungus Glomus mosseae and quanti_ed by using the~u! orescent PCR technology[ Furthermore\ DNA of Phy! tophthora infestans\ causal agent of late blight of potatoes\ was quanti_ed after extraction from arti_cially infected potato tubers and naturally infected _eld plants[ Phytophthora citricola DNA\ causing root!rot diseases\ was quanti_ed after isolation from arti_cially inoculated seedling roots of beech and oak [ The results demonstrate that novel real!time PCR techniques are a powerful uni! versal tool in modern phytopathological research[ Zusammenfassung Real!time quantitative PCR] DNA!Bestimmung in isolierten Sporen des Mykorrhizapilzes Glomus mosseae und Nachweis von Phytophthora infestans sowie Phytophthora citricola in ihren Wirtsp~anzen Es wurden spezi_sche Primer und Fluoreszenzproben zum Nachweis von Mykorrhizapilz! sowie Pathogen! U[ S[ Copyright Clearance Center Code Statement] 9820Ð0674:88:3697Ð9398 , 03[99:9 DNA entwickelt[ Der Anstieg der im Verlauf der PCR gebildeten Produkte wurde wa Ãhrend der Reaktion unter Verwendung des ABI Prism 6699!Gera Ãtes direkt gemes! sen[ Die automatische Quanti_zierung der Amplicons fand anhand der Ct!Wertbestimmung statt\ wobei ein Vergleich mit den Ct!Werten von Standardproben bekannter DNA!Konzentration erfolgte[ Der Ct!Wert ist abha Ãngig von der DNA!Menge und repra Ãsentiert den Schritt im PCR!Zyklus\ bei dem erstmalig ein Fluoreszenz! signal gemessen werden kann[ DNA wurde aus 00 bzw[ 099 Sporen des Mykorrhizapilzes Glomus mosseae extrahiert und mit Hilfe der beschriebenen PCR!Technik quanti_ziert[ Daru à ber hinaus ist die Vermehrung von Phytophthora infestans!DNA\ dem Erreger der Kraut! und Knollenfa Ãule bei der Karto}el\ in ku à nstlich in_zier! ten Karto}elknollen sowie natu à rlich in_zierten Feldp~anzen bestimmt worden[ Au)erdem wurde die DNA des Wurzelfa Ãule!Erregers Phytophthora citricola in Wurzelproben von ku à nstlich in_zierten Keimlingen der Buche und Eiche quanti_ziert[ Die Ergebnisse zeigen\ da) sich die neuen~uoreszenzgestu à tzten Techniken zur direkten Quanti_zierung von PCR!Produkten universell und leistungsfa Ãhig in der modernen phytopathologischen Forschung einsetzen lassen[

We used local microclimatic conditions and twig sap flow rates to interpret midday stomatal closure in the canopies of two 250-year-old Norway spruce (Picea abies (L.) Karst.) trees at a subalpine site in the Swiss Alps (1,650 m a.s.l.). Both trees showed midday stomatal closure on most clear summer days, despite the permanently wet soil. We used a modified Penman-Monteith formula to simulate potential transpiration of single twigs (ET(T)) based on high-resolution temporal and spatial microclimate data obtained both inside and outside the crowns. Comparison of calculated ET(T) values and measured twig sap flow rates enabled us to pinpoint the occurrence of midday stomatal closure and the microclimatic conditions present at that time. We found that vapor pressure deficit (and for upper-crown twigs, ET(T)) largely explained the timing of initial midday stomatal closure but gave no explanation for the different patterns of stomatal behavior after initial closure in upper- and lower-crown twigs. After the initial stomatal closure, upper-crown twigs maintained high transpiration rates by continuously regulating stomatal aperture, whereas stomatal aperture decreased rapidly in lower-crown twigs and did not increase later in the day. Midday stomatal closure in lower-crown twigs occurred on average 1 h later than in upper-crown twigs. However, the microclimate at the time of initial stomatal closure was similar at both crown locations except that lower-crown twigs received significantly less solar radiation than upper-crown twigs both at the time of initial stomatal closure and afterwards. High rates of sap flow in twigs did not always lead to stomatal closure and therefore could not explain the phenomenon. We conclude that stomatal conductance can be modeled accurately only when both local microclimatic conditions and tree water status are known. Further, we hypothesize that both the quantity and quality of light play an important role in the reopening of closed stomata during the day.

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