Báo cáo lâm nghiệp: "The effects of transplanting stress on photosynthesis, stomatal conductance and leaf water potential in Cedrus atlantica Manetti seedlings: role of root regeneration"

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Nội dung Text: Báo cáo lâm nghiệp: "The effects of transplanting stress on photosynthesis, stomatal conductance and leaf water potential in Cedrus atlantica Manetti seedlings: role of root regeneration"

The effects of transplanting stress on photosynthesis, stomatal conductance and leaf water potential in Cedrus atlantica Manetti seedlings: role of root regeneration 2 Kaushal J.M. Guehl G. Aussenac 1 1 P. 1 Laboratoire de Bioctimatologie et Ecophysiologie Foreshore, Station de Sylviculture et Production, INRA, Centre de Nancy, Champenoux, 54280 Seichamps, France, and 2 Department of Forestry and Natural Resources, Punjab Agricultural University, Ludhiana, 141 004 India Introduction El Nour, 198i3), considered separately, have been shown to be affected signifi- cantly by transplanting. However, a satis- Artificial forest stand establishment may factory rationale for studying effects of be achieved either with container-grown transplanting should also include valuable seedlings or with bareroot planting stock. information on the possible linkages be- Since growing seedlings in containers tween these processes and the inter- may lead to abnormal root development relationships with root regeneration after after transplanting (Aussenac et aL, 1988), transplanting. renewed attention should be given to bareroot planting. transplanting is accompanied Bareroot Materials and Methods by specific transplanting stress, that may a lead to substantial plant mortality or re- duced growth, due to the disturbance of One yr old seedl’ings were transplanted from a the functional continuity at the soil-root nursery to a glasshouse in polyethylene bags interface (Sands, 1984), or to mechanical (16 x 60 cm) containing sphagnum peat and were maintained well-watered. One yr later, in damage to roots caused by lifting the October 1985, half of the plants were lifted from plants from the nursery beds (Chung and the bags, stored for 20 h at 20°C, 100% relative Kramer, 1975). humidity and in darkness, and then planted again in similar bags. The other half (control Physiological processes, such as C0 2 plants) were maintained in the initial bags. The assimilation and translocation (Stupendick carbon dioxide
(Jones, 1985). In an A vs c plot, these 2 limita- days 2, 9, 16, 23 and then 30 after trans- on i tions are represented by the supply (Su) and planting. demand (D) functions, respectively (see Fig. 2). In experiment 2, seedlings were transplanted in minirhizotrons. The plants were given optimal fertilization and the root systems were main- tained at 20°C in order to promote root regen- Results eration. Assimilation rate measurements and root observations (number of growing roots and root elongation) were made just before trans- 1 Experiment planting (day 0) and then weekly from day 7 to day 49 after transplanting. In the transplanted seedlings, a marked Gas exchange measurements were made and parallel decline in both C0 assimila- 2 with a classical open system under standard tion and stomatal conductance occurred environmental conditions. In experiment 1, intercellular C0 concentration (c values were 2 ) i from day 0 to day 9 after transplanting calculated from the A and g data, which per- s (Fig. 1a and b); afterwards the decline mits assessment of the extent to which changes continued, but was less pronounced. The of A following transplanting are due to reduced control plants presented a decreasing diffusional supply of C0 to the mesophyll or to 2 trend of gas exchange, but the decline decreasing mesophyll photosynthetic capacity
less than in for the transplanted plants was accompa- significantly pronounced was nied by an almost constant c (Fig. 2), thus the transplanted plants. Predawn needle i indicating that, despite the parallel evolu- water potential (Fig. 1c) was affected tion of A and g the changes in Awere by transplanting, but significantly lower , s values than in the control plants occurred mainly due to an alteration of mesophyll only after day 9. The severe decline in A photosynthetic capacity. t-
Recovery of A was strictly concomitant Experiment 2 with root regeneration, but no evidence could be found to ascertain whether a Carbon dioxide assimilation A markedly functional linkage exists between these 2 and gradually decreased after trans- parameters, or whether they respond to a planting from day 0 to day 14 (Fig. 3a), third, still unknown, factor. and then, from day 14 to day 42, recov- ered its initial value. The start of recovery in A was concomitant to the beginning root regeneration (Fig. 3). References Aussenac G. & E:I Nour M. (1986) Evolution du potentiel hydrique et du syst6me racinaire de Discussion jeunes plants de c6dre, pin laricio de Corse et pin noir plantésA I’automne et au printemps. Ann. Sci. For. 43, 1-144 The results of this study support the pre- Aussenac G., Guehl J.M., Kaushal P., Granier vious findings of several authors showing A. & Grieu P. (-1988) Crit6res physiologiques that A (Stupendick and Shepherd, 1980), pour 1’6valuation de la qualitd des plants fores- g and WP (Sands, 1984; Aussenac and El s tiers avant plantation. Rev. For. Fr. 40, 131-139 Nour, 1986) are affected by transplanting H.H. & Kr,amer P.J. (1975) Absorption of Chung stress. water and 32 through suberized and unsuber- P ized roots of lobl,olly pine. Can. J. For. Res. 5, However, the decline of A due to trans- 229-235 not a consequence of re- planting was Jones H.G. (19Ei5) Partitioning stomatal and duced g but was primarily determined by , s non-stomatal limitations to photosynthesis. alterations of mesophyll photosynthesis. Plant Cell Environ. 8, 95-104 This, plus the parallel time course of A Kaushal P.K. (1987) Analyse 6cophysiologique and g might even suggest that reduced , s des effets de stress liés aux transplanta- g is the consequence of altered meso- s tions des arbres forestiers. Thesis, University of Nancy, France phyll photosynthesis. Sands R. (1984) Transplanting stress in radiata Leaf water status is not the factor re- pine. Aust. J. For. Res. 14, 67-72 sponsible for the initial decline of A and g, s Stupendick J.A.T. & Shepherd K.R. (1980) Root but it is likely to be a relevant physiological regeneration of root-pruned Pinus radiata seed- constraint. The (common?) signal that trig- lings. II. Effect of root pruning on photosynthe- gers the initial decline in A and g remains s sis and translocation. New Zealand J. For. Sci. unknown (nutritional, hormonal?). 148-158