Water stress preconditioning of black spruce seedlings from lowland and upland sites

Abstract

1994. Water stress preconditioning of black spruce seedlings from lowland and upland sites. Can. J. Bot. 72: 1511 -1518.One-year-old seedlings from two pairs of upland-lowland populations were subjected to three cycles of drought preconditioning. During a subsequent fourth cycle, preconditioned seedlings and seedlings that had been maintained under wellwatered conditions were subjected to a final soil drought. During the drought periods, small but significant differences in gas exchanges and water relations were observed between upland and lowland seedlings but the differences were not consistent either within each lowland-upland pair or over the four cycles. During the final drought period, preconditioned seedlings maintained significantly higher net photosynthesis rate, stomata1 conductance, and transpiration rate than unconditioned seedlings. In contrast, no significant differences were found in midday water potential, total sugar content, or water relations parameters between preconditioned and unconditioned seedlings. The results suggest an absence of ecotypic variation with respect to drought tolerance in black spruce. They also suggest that preconditioning in black spruce seedlings occurs mostly through the acclimation of stomata1 and photosynthetic mechanisms to drought, without active osmotic adjustment. . 1994. Water stress preconditioning of black spruce seedlings from lowland and upland sites. Can. J. Bot. 72 : 15 11 -15 18. Nous avons soumis des semis d'un an de quatre populations originant de milieux humides et secs pairCes deux a deux par sites contrastants a trois cycles d'asskchement. Au cours d'un quatrikme cycle, les semis ainsi prCconditionnCs et d'autres semis jusque la bien irriguCs ont Ct C soumis a une dernikre pCriode d'asskchement. Au cours des pCriodes d'asskchement, nous avons observC des diffCrences faibles mais significatives dans les Cchanges gazeux et les relations hydriques entre les semis des milieux humide et sec, mais ces diffkrences n'Ctaient pas consistentes dans les paires de sites contrastants, ou entre les pCriodes d'asskchement. Au cours de la dernikre pCriode d'asskchement, les semis prCconditionnCs au stress hydrique ont maintenus des niveaux de photosynthkse, de conductance stomatique et de transpiration supirieurs a ceux non prCcondition-nCs. Par contre, aucune diffkrence n'a pu Ctre observCe dans les mesures de potentiel hydrique du xylkme de midi, de contenu en sucres totaux ou de paramktres des relations hydriques. Les rCsultats suggkrent l'absence de variabiliti Ccotypique en ce qui a trait a la tolCrance au stress hydrique chez 1'Cpinette noire. I1 semble aussi que l'acclimatation au stress hydrique se produit principalement par l'acclimatation des mCcanismes stomatique et photosynthCtique, sans qu'il n'y ait d'ajustement osmotique actif.

The dependence of water potential in shoots of <i>Picea abies</i> on air and soil water status

“…Of course, other physiological mechanisms may be involved in the trees' acclimation to drought as well. Zine E1 Abidine et al (1994) found that drought preconditioning enabled seedlings of Picea mariana (Mill.) BSP to maintain a substantially higher level of stomatal conductance and photosynthesis during a severe water stress as compared to unconditioned seedlings, but this eect was not accompanied by any changes in the concentration of osmotically active solutes.…”

Ectomycorrhizal fungal communities of black spruce differ between wetland and upland forests

“…Drier upland soils often exhibit a root-restricting clay horizon near the surface that perches the water table during wet periods of the year, leading to seasonal cycles of moisture surplus and deficit (Krestov et al 2000). Upland trees often appear more robust than their wetland counterparts; however, improved edaphic conditions do not seem to result in ecotypic variation in black spruce morphological features or water relations (Parker et al 1983;Zine El Abidine et al 1994). Results from greenhouse and field experiments with Norway spruce (Picea abies (L.) Karst.)…”

Changes inEucalyptus camaldulensisessential oil composition as response to drought preconditioning

“…Different irrigation regimes at nursery stage are commonly used to modify eucalypt seedlings quality through short-and long-term physiological and morphological changes that might allow plants to overcome stress conditions during establishment (Zine El Abidine et al 1994;Guarnaschelli et al 2003). Manipulation of nursery environment can also alter plant chemical composition, particularly its essential oil.…”