The influence of water deficits on needle conductance, assimilation rate and abscisic acid concentration of seedlings of Pinus radiata D. Don

Abstract

Seedlings of Pinus radiata, 10–20 weeks old and hitherto fully watered, responded rapidly when water was withheld. Wilting occurred 9d later, at which time soil matric water potential at dawn (Ψm) was –1.06MPa and shoot water potential (Ψ) was –1.9 MPa. Small reductions in Ψm elicited large responses in assimilation rate (A) and leaf conductance to water vapour (g). Seedlings appear to be more sensitive to small water deficits than are older Plants of P. radiata. After rewatering, significant increases of A and g occurred within one day, but neither regained the values measured prior to the imposition of a single drying cycle. This residual effect of drought on A, after one or six drying cycles, was partially caused by a decrease in photosynthetic capacity. In plants wilted for the first time, the concentration of abscisic acid (ABA) in the bulk foliage increased 3.4 times as Ψ decreased to –1.77 MPa. In comparison, pretreatment with six drying cycles significantly reduced Ψ to –2.13 MPa (indicating some osmotic adjustment) and induced only a doubling of ABA concentration. However, these differences in Ψ and ABA concentration did not Persist after the plants of all pretreatments had been watered for 7 d, although g of drought‐pretreatment Plants remained approximately half that of continuously‐watered plants.

Quantitative analysis of abscisic acid in needles of Abies alba Mill. by electron capture gas chromatography

“…With 500-1000 ng/g fresh weight (FW) the amounts of c-ABA are comparable to results from the literature, when analyses are performed with GC or GC-MS (Squire et al 1988;Johnson and Ferrell 1982;Puttonen 1987;Webber et al 1979;Naumann et al 1988). In contrast the concentrations of t-ABA (400-700 ng/g FW) are much higher than those cited for conifer needles in previous papers (Johnson and Ferrell 1982;Naumann et al 1988).…”

“…Thus an unequivocal quantitative determination with a detection limit of about 0.1 ng was achieved without further purification by High-Performance Liquid Chromatography (HPLC). GC-ECD was the most frequently employed method for quantification of ABA in coniferous needles (Little et al 1978;Sandberg et al 1981;Johnson and Ferrell 1982;Oden and Dunberg 1984;Frenzel et al 1987;Puttonen 1987;Squire et al 1988;Naumann et al 1988). A chromatogram of the purified extract using optimai separation conditions is shown in Fig.…”

Effect of cold storage treatments and transplanting stress on gas exchange, chlorophyll fluorescence and survival under water limiting conditions of Pinus radiata stock-types

“…The ability of newly planted seedlings to maintain photosynthesis is related to their water status (Kozlowski et al 1991;Kubiske and Abrams 1992;Mena-Petite et al 2000). Radiata pine seedlings are very sensitive to water deficit (Squire et al 1987(Squire et al , 1988. As water deficit increased, both assimilation and stomatal conductance decreased practically in parallel (compare Figs.…”

Influence de la dur�e d'acclimatation sur l'endurcissement � la s�cheresse d'Acacia cyanophylla Lindl.

“…À partir de 3 mois, l'évolution des paramètres mesurés chez les plants témoins et stressés, atteste chez ces derniers d'une tolérance au manque d'eau croissante au cours du temps (turgescence de plus en plus élevée pour un même niveau de Ψ min, des seuils de turgescence nulle et de fermeture stomatique plus négatifs et de plus en plus bas). Des effets comparables de l'acclimatation à la sécheresse ont été observés chez certaines essences forestières telles que Cajanus cajan [16], Picea glauca et Pinus banksiana [17], Ceratonia siliqua [28], Pinus taeda [31], Pinus radiata [32], Picea mariana [12,34,41] ou divers clones de Peuplier [38]. D'autre part, le maintien, chez les plants acclimatés, de g s à des valeurs plus faibles que celles des plants témoins pour des Ψmin supérieurs à -2,2 MPa puis à des valeurs plus élevées pour des Ψ min plus bas témoigne d'une meilleure régulation stomatique chez les plants acclimatés comme cela a été signalé chez Populus deltoïdes [30], Pinus halepinsis [40] et Picea mariana [41].…”