0» V.MPV* of**1 in Plant Science 1 OSAprl Xlt!. 0t» 10 33Bft-m?Ot5Xei1 An improved method for the visualization of conductive vessels in Arabidopsis thaliana inflorescence stems Hade* Jupa'. Vofiach tt*mmaHclwaum k*mi* ama aacn mmfc OPEN ACCESS FtaMfctsamwm. liwryr ■ Z6ff 370ma mi vacs Mi MmaaaiD ftcnnt* Dye perfusion is corrmonJy used for the identification of conductive elements mumlaut for the study of xyiem development as well as precise hydraufcc estimations. The tiny size of nflorescence stems, the smal amount of vessels n close arrangement, and htgh hydraufcc reswtrvity delimit the use of the method for quantification of the water conductivity of Arafairfqpsts thakana. one of the recently most extensively used plant models. Here, we present an extensive adjustment to the method in order to reliably identify ndnrtdual functional (conductive) vessels. Segments of inflorescence stems were sealed m silicone tjbes to prevent damage and perfused with a dye solution Our results showed that dyes often used for staining functional xyiem elements (safranin. fuchsme. tducfcne blue) fated with ArabidDpsis. In contrast. Fluorescent Bnghtener 28 dye solution perfused through segments stared secondary oefl wals of functional vessels, which were dearly cfcsbnguishable m native cross sections. When compared to identification based on the degree of development of secondary cell wals. identification with the help of dye perfusion revealed a significantly lower number of functional vessels and values of theoretical hydraulic conductivity We found that fcgnified but not yet functional vessels form a substantial portion of the xyiem in apical and basal segments of Arabidopsis and. thus, agnifcantty affect the analyzed functional parameters of xyiem The presented methodology enables ratable identification of individual functional vessels, dtowing thus estmations of hydraulc conductivities to be improved, see datrtautions and vessel dkmetera to be refined, and data variability generally to be reduced. forsutfogy OG 1-10 •093/lTMphyitpwOe „„.„no***11 -,101m"1I", 1BU Research paper Partitioning of vessel resistivity in three liana species Milan Balaz1 * Radek Xjpa1, Steven Jansen2 Alexander Cobb3 and V.t Gloser1 ^I«m4&pM L) and used elastomer *iject>on for identification of open vessels and for measurement of changing vessel inner da-meters along its a 10 The relative contribution of end wal resistivity to total vessel resistivity was 0 46 for hop, 0 55 for grapevine and 0.30 for clematis Vessel lumen resistivity calculated from our measurements was substantially higher than theoretical resistivity about 43% for hop. 58% for grapevine, and 52% tor clematis We identified variation in the vessel inner diameter as an important source of vese! ressttvity. The coefficient of variation of vessel inner diameter was a good predictor for the ncrcase of the ratio of integral nY„> to n*„ calculated from the mean value of inner vessel cfcameter We discuss the fact that we dealt with the longest vessels in a given stem sample, which may lead to the over estimation of vessel lumen resistivity, which consequently precludes decision whether the variable vessel ainer diameter expJans fully the difference between vessel lumen resistivity and we observed Keywords: Gemot-S vitofco Mumufc,s JupuAn, hydraulic conductivity resistivity variable diameter. Vits vn*ero, lytei Vessels wffh simple perforation plates are Bie pr nopal lylcm conduts m a majcrty of angosperms and are beaeved to impede sap How less than conduits weh evokibonanry older plate types (Becker el al 1999. fcVodnbb and reiki 2000, Spcrry 2000. More er 2002. Sack et al 2003. Sperry et al 2003. Brodnbbetal 2005). However, even in speoes bearing vessel* with simple perforabon plates, experimental measurements of hydraulic conductvty (K. volume Dow rale of water per pressure gradient. m*s ' MPa ') on stem segments wth-out open vesseh (i.e. vessels tadung both end wals) rypicaty yield vaajes less than haf those Prxsemle (HP) equatK- (Gaydano et a 1978. Tyree and Ei Ewers 1992. Hargrave et al 1994. Mai Tyiee and Zimmermann 2002. Sperry etal 2011). Ths discrepancy a I least fading adaptive pressures on xytemstrui oency and safety against emboasm. sin. k^ngth, density, and Viree-dimeni oonduts (Wheeler el al 2005. Hacke el 2006. Owe etal. 2009). Conventionsly, two main contrbutior 10.1 Ul/ppU 3*35 ECOPHY5IOLOGY. STRESS AND ADAPTATION Do angiosperm tree species adjust intervessel lateral contact in response to soil drought? Radek Jupa12 | Dita Krabičková1 | Roman Plichta2 | Stefan Mayr3 | Vít Gloser1 'OlMrtmertt of EiqjřfimcnW Bijlocv F* Brno. Cied RepuH* 'Department of Forest Botany Dendrology mo CeobwJCCfiologv fteuty ol Forr-ttrv »nd Wood Tethnotafv. Mni*l U««rW» m Bmo Brno. CtKh ReeuUk Radci Jucu Departmnv of f KperUncinaJ BlotOfV Fatuity «* Soenf e M auryi Unnr*rvt> Kamenice S, 62500 Brno. Cmh Iptfe Email tjuo**nuá.ituni ti fundng i plan o( the MendH University In Bmtv Grant'Award Number pott-doc protect 7 3. kHotrw! Grant Agency MENDEIU. Grant/ Award Humtwr UDF KV 2018003. Mmlrv of Education Youth and Soort> of the Ciecti Republic Cnm'Award Niimber ITT20017 Edttcd by J M Torm-ftuu Abstract During soil drought fi.e limited soil water availability to plants), woody species may adjust the structure of their vessel network to improve their resistance against future soil drought stress Impacts of soil drought on intervessel lateral contact remain poorly understood despite of its significance to xyfem transport efficiency and safety. Here, we analysed drought-induced modifications in xylem structures of temperate angiosperm trees with a focus on intervessel lateral contact. Anatomical analyses were performed both in stems of seedlings cultivated under different substrate water availability and annual rings of mature individuals developed during years of low and high sol drought intensities. In response to limited water availability, a decrease in vessel diameter (up to 20%) and simultaneous increase in vessel density (up to -60%) were observed both in seedlings and mature trees. Conversely, there were only small and inconsistent drought-induced changes in intervessel contact frequency and intervessel contact fraction (typicaly up to t1S%] observed across species, indicating that intervessel lateral contact is a conservative trait. The small adjustments in intervessel lateral contacts were primarily driven by changes in the contact frequencies between neighbouring vessels (i.e. vessel grouping) rather than by changes in proportions of shared cell walls. Our results demonstrate that angiosperm tree species, despite remarkable adjustments in vessel dimensions and densities upon soil drought, exhibit surprisingly invariant inlervessel lateral contact architecture. INTRODUCTION Soil drought (i.e. j penod of iiroted soil water availability to plants) <* a phenomenon with adverse effects on plant growth, development, and health (Upier. et al 2013: Mrttlcr, 2006) In the last decades, increasing frequency and extent of soil droughts combined with intensive heat nave* affected the health of forest stands and contributed to their decline in various regions of the earth (Allen et »1- 2010. 2015: Hartmann et at. 2018} Severe soil droughts can affect the species convpowOon and structure of forests, after ecosystem lurv: and may have enormous consequences for carbon cycling (AJten et al. 2015: MBlar & Stephenson, global and regional climate models predict tl to become even more frequent underslanding of tree responses to water shortage is urgently needed for assessing and reducing the impacts of ongoing ctimatk change on forests (Coll et aU 2018. Sousa-SJva et at. 2018). Tree resistance to soil drought is tightly inked with lions (ChoM lytai chekW. ree resistance to sou arougnt is ugiiuy omca w gfjfc* / (Choat et 2012. 2018: McDowell et^h/^RĚ^^^^^^^L / i provides long-distance transport q^^H •ds leaves in a system of capilljry^^^H PŘÍROD DOVĚDECKAFAKOLTA Zvyšování odolnosti zemědělských plodin vůči suchu využitím vlastností p\aně rostoucích příbuzných óruhů \e douch Bakalářská práce ŠIMON JÁGER . RNDr. Radek Jupa 'álni k^iogie Ph.D. t\ D P°l i Tree Physiology, 2023. 1-12 https://doi.or9/lO.l093yireaplivs/tpadl32 Research paper Bark wounding triggers gradual embolism spreading in two diffuse-porous tree species Radek Jupa" and Kamila Pokorná Department of Experimental Biology, Faculty of Science, Masaryk University, Kamenice 5, Brno CZ-62500, Czech Republic "Corresponding author inupairmail mum c:i Handling Edrtor Teemu Holtta Xylem transpon ts essential for the growth, development and survival of vascular plants Bark wounding may increase the risk of xylem transport failure by tension-driven embolism However, the consequences of bark wounding for xylem transport are poorly understood. Here, we examined the impacts of the bark wounding on embolism formation, leaf water potential and gas exchange in the terminal branches of two diffuse-porous tree species lAcer platanoides L and Prunus avium L) The effects of bark removal were examined on field-grown mature trees exposed to increased evaporative demands on a short-term and longer-term basis (6 h vs 6 days after bark wounding) Bark removal of 30% of branch circumference had a limited effect on the xylem hydraulic conductivity when embohzed vessels were typically restricted to the last annual ring near the bark wound Over the 6-day exposure, the non-conductive xylem area had significantly increased in the xylem tissue underneath the bark wound (from 22-29% to 51-52% of the last annual ring area in the bark wound zone), pointing to gradual yet relatively limited embolism spreading to deeper xylem layers over time In both species, the bark removal tended to result in a small but non-signrficant increase in the percent loss of hydraulic conductrvrty compared with control intact branches 6 days after bark wounding (from 6 to 8-10% in both species) The bark wounding had no significant effects on midday leaf water potential, C02 assimilation rates, stomatal conductance and water-use efficiency of the leaves of the current-year shoot, possibly due to limited impacts on xylem transpon The results of this study demonstrate that bark wounding induces limited but gradual embolism spreading. However, the impacts of bark wounding may not significantly limit water delivery to distal organs and leaf gas exchange at the scale of several days Keywords: drought gas exchange, hydraulic conductrvrty. tree injury, water potential, xylem Introduction Long-distance xylem transport of water and solutes represents a process or viral importance tor all vascular plants (Tyrcc and Zimmermann 2002, Choat ct al. 2018). Xylem transport is carried out under a negative pressure gradient in a system of non-living xylem conduits (vessels or tracheids; Stroock ct al. 2014). Under these physiological conditions, the water column in the xylem conduits is under permanent tension, and the transport is prone to failure by embolism (Zwicniecki and Sccchi 2015, Choat et al. 2018). Extensive formation of rension-driven embolism is typically associated with drought stress exposure when increased tension in the xylem accelerates embolism spreading in the network of xylem conduits. During embolism spreading, air expands from one xylem conduit to a neighboring one through pits, resulting in an inability of such a conduit to transport water (Zwicniecki and Sccchi 2015). Extensive spreading of embolism finally results in the critical loss of xylem conductivity and, consequently, limirs watc^*-livery to distal organs. The impaired water ■•"Pply^^^^^^^'' suppress carbon uptake iN.in.lmi and ' al. 2020) and, in extreme CMfll conduits at a given tension. In particular, the mutual connectivity of xylem conduits leg., vessel grouping and intervessel pitfield fraction | and pit ultra structure (e.g.. tonis-to-apcrturc overlap, intervessel pit membrane dimensions and size of pore constrictions in intervessel pit membranes) belong to the prominent determinants of embolism spread within xylem (Wheeler et al. 2005, Bouchc ct al. 2014, Li ct al. 2016, Kaack et al. 2021, Levionnois et al. 2021). By contrast, very little is currently known about the functional significance of bark for undisturbed xylem transport. However, several lines of evidence suggest that bark integrity and its functional properties may mitigate uncontrolled increases in xylem tension and, together with xylem structural traits, affect xylem vulnerability to embolism. The bark is a multifunctional structure of complex ontogenetic origin, which refers to a collection of all tissues outside the secondary xylem (Angyalossy ct al. 2016). In the bark, the inner and outer hark regions are distinguished i their **-^__^^^k.^L^^ Inferences (Rosell 2J|' • irmcd In a t