Báo cáo lâm nghiệp: The influence of acid mist upon transpiration, shoot water potential and pressure—volume curves of red spruce seedlings

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Báo cáo lâm nghiệp: "The influence of acid mist upon transpiration, shoot water potential and pressure—volume curves of red spruce seedlings" The influence of acid mist upon transpiration, shoot water potential and pressure—volume curves of red spruce seedlings D. Fowler D. Eamus I. Leith Penicuik, EH 26 OOB, Scotland, U.K. Bush Estate, Institute of Terrestrial Ecology, 16-20°C. On 16/7/87 100 seedlings were Introduction inside each of 8 open top chambers placed (OTCs) at a site in Scotland, U.K. (55°50’N; Widespread forest decline has been docu- 2°13’W; 200 m altitude). Four different pH treat- mented in Europe and NE-U.S.A. (John- ments (pH 2.5, 3.0, 4.0 and 5.0) with simulated son, 1987; Woodman, 1987). This decline acid mist were supplied using dilutions of an equimolar solution of (NH and HN0 Q SO Z ) 4 - 3 increases with increasing altitude (Mc- Each chamber received twice weekly sprays Laughlin, 1985). One hypothesis to ex- with an equivalent of 2 mm precipitation per plain the decline and its altitude depen- spray. Spraying commenced on 24/7/87 and dence is that excessive proton input has a continued until 20112187. deleterious effect upon tree growth. Acid The following measurements were made: 1) input to the foliage and soil via wet and shoot water potential was determined at 09:00 dry deposition may be a major factor in h on 23/10/87 using a portable Scholander causing decline directly or indirectly by pressure bomb (Hellkvist et al., 1974). Eight replicate branches from pH ?-.5, 3.0, 4.0 and 5.0 predisposing the tree to additional biotic treated trees were measured. 2) Day and night and/or abiotic stress factors. transpiration rates were determined on 16/11/87 The maintenance of a favorable water for 10 entire seedlings, of pH 2.5 and pH 5.0. status is a priority for continued growth treatments and 10 attached shoots enclosed in a cuvette. 3) Eight replicate shoots (rehydrated and survival, and many of the symptoms overnight as attached branches) from pH 2.5, associated with forest decline (crown thin- 3.0 and 5.0 treated seedlings were subjected to ning, root necroses) may be expected to pressure-volume analysis (Kim and Lee-Sta- influence plant water status. This paper delmann, 1984; Stadelmann, 1984). presents some of the results of a detailed study of the influence of acid mist on the water relations of red spruce seedlings. Results Materials and Methods Fig. 1 shows that branch water potential (’Pw) decreased from !.07 to -1.2 MPa as germinated and grown Red spruce seeds were treatment pH decreased from 5.0 to ?-.5. for 16 mo in a greenhouse maintained at Day and night transpiration rates were1.19 ± 0.06 mmol (day) and ...