Photosynthetic efficiency of Pedunculate oak seedlings under simulated water stress

Abstract

Photosynthetic performance of seedlings of Quercus robur exposed to short-term water stress in the laboratory conditions was assessed through the method of induced fluorometry. The substrate for seedlings was clayey loam, with the dominant texture fraction made of silt, followed by clay and fine sand, with total porosity 68.2%. Seedlings were separated in two groups: control (C) (soil water regime in pots was maintained at the level of field water capacity) and treated (water-stressed, WS) (soil water regime was maintained in the range of wilting point and lentocapillary capacity). The photosynthetic efficiency was 0.642±0.25 and 0.522±0.024 (WS and C, respectively), which was mostly due to transplantation disturbances and sporadic leaf chlorosis. During the experiment Fv/Fm decreased in both groups (0.551±0.0100 and 0.427±0.018 in C and WS, respectively). Our results showed significant differences between stressed and control group, in regard to both observed parameters (Fv/Fm and T½). Photosynthetic efficiency of pedunculate oak seedlings was significantly affected by short-term water stress, but to a lesser extent than by sufficient watering.U radu je analizirana fotosintetička efikasnost sadnica Quercus robur, izloženih kratkotrajnom vodnom stresu u laboratorijskim uslovima, metodom indukovane fluorimetrije. Kao supstrat za gajenje sadnica korišćena je glinovita ilovača, čiju je dominantnu teksturnu frakciju činio prah, zatim glina pa sitan pesak; totalne poroznosti 68,2%. Sadnice su bile podeljene u dve grupe: S (kontrolna grupa, kod kojih je vodni režim supstrata u saksijama održavan na nivou poljskog vodnog kapaciteta) i WS (grupa izložena vodnom stresu, kod kojih je vodni režim supstrata održavan između tačke venjenja i lentokapilarnog kapaciteta). Fotosintetička efikasnost iznosila je 0,642±0,258 kod kontrolnih sadnica, odnosno 0,522±0,0243 kod izloženih vodnom stresu, što je uglavnom bilo uzrokovano poremećajima izazvanim presađivanjem kao i pojavi hloroze na listovima. Tokom eksperimenta, vrednost Fv/Fm se smanjila u obe grupe sadnica (0,551±0,0100 kod C, odnosno 0,427±0,018 kod WS). U oba merenja utvrđene su statistički značajne razlike između stresirane i kontrolne grupe sadnica u pogledu ispitivanih parametara. Izlaganje sadnica hrasta lužnjaka kratkotrajnom vodnom stresu imalo je značajan uticaj na smanjenje fotosintetičke efikasnosti sadnica, ali u manjoj meri nego izlaganje sadnica obilnom zalivanju.Projekat ministarstva br. TD2005