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Báo cáo lâm nghiệp: "of stem cuttings of Populus x euramericana under different water potentials"

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Tuyển tập các báo cáo nghiên cứu về lâm nghiệp được đăng trên tạp chí lâm nghiệp Original article đề tài: of stem cuttings of Populus x euramericana under different water potentials...

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of stem cuttings of Populus x euramericana Rooting under different water potentials 1 S. Puri 2 Thompson F.B. 1 Department of Forestry, Haryana Agriculture University, Hisar125 004, India, and 2 Forestry Institute, South Parks Road, Oxford OX1 3RB, U.K. Oxford at 70% and illumi- growth chamber at 25°C, RH Introduction nation of 1000 foot candles for 16 h. The cut- tings were assessed for shoot and root de- The rooting of stem cuttings is affected by velopment, moisture content, water and osmotic potentials, stomatal diffusion resistance, relative many environmental factors (Haissig, conductivity and starch content. 1974; Puri and Shamet, 1988). The main- Water potentials of shoots ( shoot) were V tenance of water balance is one of the measured with a pressure chamber (Scholan- important factors. The water balance of der et al., 1964) and those of bark (qJ bark) cuttings is affected by high transpirational according to the Shardakov method. Osmotic water losses coupled with either low water potential (’P solute) was measured with a Wes- cor C52 chamber hygrometer connected to a absorption or slow water transport through Wescor HR-33 T microvolt meter. The relative the conducting tissues. However, little is conductivity of the root system and base of known about maintenance and control of each cutting was estimated according to the plant water potential during the rooting of procedures of Ikeda and Suzaki (1984). Starch was extracted from the stem following the cuttings. The present studies were under- method of Dekker and Richards (1971) and was taken to examine rooting as influenced by estimated after hydrolysis to glucose by the initial plant water potential. method of Kilburn and Taylor (1969). Results were subjected to a standard analysis of vari- procedure using a split plot design. ance Materials and Methods Results and Discussion Variation in the initial plant water potential (4!P) of Populus x euramericana was obtained by 3 pretreatments, viz., fresh, soaked (5 d in water) Root initiation per se in poplar is not an and dried (7 d old cuttings kept in the open). Ini- obstacle to propagation, but moisture sup- tial W were -1.45, - 0.1 and -2.1 MPa, respec- p tively. Cuttings were planted in a mixture of peat ply has a major effect on successful root- and grit sand (1:1, v/v), maintained at -0.006 ing. The water stressed cuttings had fewer and -0.06 MPa by weighing the pots daily and roots and these grew slowly (both in num- adding water to restore these soil moisture ber and length) as shown in Table I. Pre- potentials. Tensiometers were also used as a soaking stimulated rooting and enabled check. The pots with cuttings were kept in a
cuttings to absorb water for initial root soaked cuttings it decreased. This result development, even under the drier soil may be due to the high initial 7 of soaked 1 conditions (-0.06 MPa). The stem mois- cuttings. Once well-developed roots were ture of fresh and dried cuttings increased formed, the v!of shoot and bark stabilized, with time. The moisture content of soaked irrespective of pretreatment. cuttings decreased initially, presumably The turgor pressure more or less fol- due to high initial moisture, and later lowed the pattern of y solute but exag- ’ increased. The root moisture content gerated any rise of potential, due to the increased initially and then decreased in fall in ’P bark ofl:en associated with rises in all the treatments. This is attributed to the osmotic potential of the expressed sap. observation that, during early develop- The relative conductivity decreased initial- ment of roots, only cell elongation and cell ly and then increased gradually. This division occur, and later on cell differentia- decrease may be due to decreased water tion, lignification and hardening begin absorption by the cuttings until the func- (Esau, 1960). tional roots were formed. Grange and Changes in shoot water potential, rela- Loach (1983) opined that the decrease in tive conductivity and starch are given in water absorption of cuttings with time may Table I. The water potential of fresh and be due to increased resistance to water dried cuttings increased with time but for influx through the cut surface.
Esau K. (1960) In: Anatomy of Seed Plants. as the prime carbohydrate Starch acts John Wiley & Sons, New York pp. 569 for root initiation and development source Grange R.I.& Loach K. (1983) The water econ- (Haissig, 1974). In the present studies, it omy of unrooted leafy cuttings. J. Hortic. Sci. decreased with time irrespective of treat- 58, 9-17 ment (Table I). This decrease may be at- Haissig B.E. (1974) Metabolism during adventi- tributable to the export of starch to devel- tious root primordium initiation and develop- ment. New Zealand J. For. Sci. 4, 324-337 oping roots and leaves. Ikeda T. & Suzaki T (1984) Distribution of xylem Although our observations were limited resistance to water flow in stems and branches single species and few treatments, to a of hardwood species. J. Jpn. For. Soc. 66, 229- they suggest that the levels of water 236 stress imposed on the cuttings significant- Kilburn D.M. & Taylor P.M. (1969) Effect of sulf- hydryl reagents on glucose determination by ly influenced rooting. the glucose oxidase method. Anaf. Biochem. 27, 555-558 Puri S. & Shamet G.S. (1988) Rooting of stem cuttings of some social forestry species. Int. Tree Crops J. (U.K.) 5, 63-70 References Scholander P.F., Hammel H.T., Hemmingsen E.A. & Bradstreet E.D. (1964) Hydrostatic pres- sure and osmotic potentials in leaves of man- Dekker R.F.H. & Richards G.N. (1971) Determi- groves and some other plants. Proc. Natl. nation of starch in plant material. J. Sci. Food Acad. Sci. USA 51, 119-125 Agric. 22, 441-451

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