Morphological and physiological responses of oak seedlings (Quercus petraea and Q. robur) to moderate drought

Abstract

To cite this version:Frank Thomas, Thomas Gausling. Morphological and physiological responses of oak seedlings (Quercus petraea and Q. robur) to moderate drought. Annals of Forest Science, Springer Verlag/EDP Sciences, 2000, 57 (4) Abstract -To study their responses to a moderate drought, seedlings of sessile (Quercus petraea [Matt.] Liebl.) and pedunculate oak (Q. robur L.) were grown in outdoor lysimeters that allowed unrestricted root growth. They were subjected to a moderate drought from mid-June to the end of August. The stomatal conductance remained almost unaffected by drought. In the drought-stressed seedlings, the relative foliar water deficits were significantly higher, and the predawn leaf water potentials were significantly lower than in the control plants. The decrease in osmotic pressures at maximum turgor and at the point of turgor loss in the drought-stressed plants indicated osmotic adjustment. The ratio of leaf to fine-root biomass was significantly diminished in the drought-stressed seedlings. In combination with previous observations, the results indicate that, in the Central-European oak species, a shift in biomass compartmentation is the predominant process in acclimation to drought since it also occurs under severe drought stress in contrast to osmotic adjustment, which was only found under conditions of a moderate drought. Quercus / drought / leaf-root biomass ratio / osmotic adjustment / pressure-volume analysisRésumé -Réponses morphologiques et physiologiques de semis de chêne (Quercus petraea et Q. robur) face à une sécheresse modérée. Afin d'étudier leur réaction face à une sécheresse modérée, des plantules de chêne sessile (Quercus petraea [Matt.] Liebl.) et de chêne pédonculé (Q. robur L.) ont été cultivées à l'extérieur, dans une cuve lysimétrique permettant un développement illimité des racines. Le régime de sécheresse modérée leur a été appliqué de mi-juin jusqu'à fin août. La conductance foliaire stomatique n'a guère été affectée par la sécheresse. Le degré du déficit hydrique foliaire relatif des plantules stressées par la sécheresse avait augmenté de façon significative alors que le potentiel hydrique foliaire mesuré avant l'aube fut plus bas que celui des plantules témoins. La diminution des pressions osmotiques en pleine turgescence et au point zéro turgor des plantules stressées indiquerait un ajustement osmotique. Les plantules stressées ont montré un ratio de la biomasse foliaire par rapport à la biomasse des racines fines qui avait baissé de manière significative. Les résultats complètent ainsi des études antérieures indiquant que pour les chênes européens le changement de la compartimentation de la biomasse serait le processus prédominant dans l'acclimatation à la sécheresse. En effet, ce phénomène surgit également lors d'une sécheresse excessive tandis que l'ajustement osmotique n'a été constaté que lors d'une séche-resse modérée.Quercus / ajustement osmotique / analyse pression-volume / rapport des biomasses feuilles-racines / sécheresse Ann. For. Sci. 57 (2000) 325-3...

Adaptive genetic variability and differentiation of Croatian and Austrian Quercus robur L. populations at a drought prone field trial

“…This argument is supported by the fact that the same populations grown in another field trial in Croatia, where it were exposed to less pronounced aridity, showed remarkably greater mean heights compared to those found in the present study (Popovic et al 2014). Reduced humidity tends to decrease the height growth of pedunculate oak (van Hees, 1997, Thomas & Gausling 2000, Arend et al 2011; thus, it can be assumed that the relatively low heights of the populations at the studied trial were at least partially a result of the water availability deficit to which the populations were exposed over the period -2012. Valkonen (2008 reported that the average survival of pedunculate oak saplings at the age of five years under different treatments at different localities of field trials in Finland was above 73%.…”

Water relations of cork oak (Quercus suber L.) seedlings in response to shading and moderate drought

“…The scarcity of rainfall during this season is generally associated with large solar radiation loads [52]. When soil water is gradually depleted, physiological mechanisms of drought tolerance, including stomatal control of water loss, osmotic adjustment [35] and development of hydraulic systems resistant to cavitation [39,47], bring into play turgor maintenance and prevention of water loss [13,25,28,49,50]. Indeed, drought tolerance in Mediterranean areas has a relevant impact on the physiological response of seedlings, even under shade conditions [53].…”

Ecophysiological and biochemical responses of saltbush subjected to salinity

“…At 45 days, mean values of 1.44 KPa, 1.34 KPa and 1.12 KPa were observed respectively for levels of 300 mM, 450 mM and 600 mM of NaCl. It has been found that the increase in VPD leaf-air , when the plant is under water/salt stress, reduces the water vapor flow in the substomatal chamber to the atmosphere, causing reduction in the stomatal conductance and transpiration (Thomas & Gausling 2000). However, in the present study, the reduction in VPD leaf-air along the time under salt stress imposition seems to have favored saltbush plants to maintain small stomatal opening and transpiration rates at levels consistent with the salinity conditions to which they were exposed.…”