20.500.12556/RUL-173122 Odziv listnih rež sadik doba (Quercus robur) in gradna (Q. petraea) na spremembe vlažnosti zraka Stomatal response of pedunculate oak (Quercus robur) and sessile oak (Q. petraea) seedlings to changes in air humidity S spreminjajočim se podnebjem pridobiva na pomembnosti odpornost vrst na sušo, ki ni vedno le posledica pomanjkanja vode v tleh. Kot problem se vedno bolj kaže sušenje ozračja, tj. višanje deficita tlaka vodne pare zraka (VPD), ki pospešuje evaporacijo in transpiracijo. Rastline se na zaostrene razmere navadno odzovejo z zapiranjem listnih rež, s čimer zmanjšajo izgube vode ter ohranjajo turgor in hidravlično prevodnost, a na račun manjšega sprejema ogljikovega dioksida in fotosinteze. Da bi preučili odzivanje hrastov doba (Quercus robur) in gradna (Q. petraea) na tovrstne zahtevne razmere, smo postavili lončni poskus s 30 sadikami. V juliju 2024 smo izbrali dva dneva z izrazitim porastom VPD-ja v opoldanskem času in izmerili prevodnost listnih rež, transpiracijo, VPDlist in fotokemično učinkovitost. Majhna prevodnost, visok VPDlist in nizka fotokemična učinkovitost še posebej v opoldanskih in zgodnjih popoldanskih urah so nakazovali, da so bile rastline v zahtevnih razmerah izpostavljene stresu. Statistično značilnih razlik v opoldanski prevodnosti listnih rež med dobom in gradnom nismo zaznali. Za primerjavo z nekoliko običajnejšimi vrednostmi smo meritve v opoldanskem času ponovili še en dan v avgustu leto kasneje, ko so bile razmere občutno milejše. Slednje se je odražalo na opazovanih parametrih, vendar razlik med vrstama spet ni bilo zaznati. Če bi želeli ugotoviti, ali med vrstama prihaja do odstopanj pri odzivu na atmosfersko sušo, bi bile potrebne nadaljnje študije. Plant drought tolerance has a significant impact on survival in a changing environment. Atmospheric drying, i.e. raising vapour pressure deficit, has become an important driver of plant-water relations, as it increases both evaporation and transpiration. Plants respond to higher evaporative demand by closing their stomata, thereby lowering water loss by transpiration and maintaining turgor levels and hydraulic conductivity, but at the cost of a decreased carbon dioxide uptake and photosynthetic rate. To study the response of two oak species, pedunculate (Quercus robur) and sessile oak (Q. petraea), to harsh environmental conditions, an experiment with 30 seedlings was carried out. We focused on hot dry days with a significant increase of midday VPD values. Stomatal conductance, transpiration, VPDleaf and photochemical efficiency were measured on two days in July 2024. These stressful conditions led to low stomatal conductance, high VPDleaf and low photosynthetic efficiency, which indicated the stress the seedlings were under. No statistically significant differences in midday stomatal conductance between the species were found. To compare the results with values in milder conditions, another series of measurements was made on a less extreme day in August 2025. While the conditions were notably milder, no differences between the species were found that day either. To determine whether the two oak species differ in their responses to atmospheric drought, further studies would be needed. hrast deficit tlaka vodne pare (VPD) prevodnost listnih rež sušenje ozračja oak vapour pressure deficit (VPD) stomatal conductance atmospheric drying true false false [T. Pepelnjak] Slovenski jezik Angleški jezik Diplomsko delo/naloga 2025-09-13 08:15:56 2025-09-13 08:16:00 2025-11-04 04:06:45 0000-00-00 00:00:00 2025 0 0 0000-00-00 NiDoloceno NiDoloceno NiDoloceno 0000-00-00 0000-00-00 0000-00-00 630*18:630*17(043.2)=163.6 264008 249121027 51086.pdf 51086.pdf 1 A1EA06B432C59EDFBF20BCFD754B8C2D de39cb8483f7d8ce15db00a0396fa12a07dbb850b6bcb5bd9cfde97c4d7bb1cf f3ae1e33-9068-11f0-9328-0050569b8976 https://repozitorij.uni-lj.si/Dokument.php?lang=slv&id=217291 Biotehniška fakulteta 0 0 0