Báo cáo lâm nghiệp: "Morphological and physiological micropropagation"

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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: Morphological and physiological micropropagation...

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Nội dung Text: Báo cáo lâm nghiệp: "Morphological and physiological micropropagation"

Morphological and physiological lesions induced by micropropagation C.J. Atkinson K. Oates 1 A. Harbour 1 W.J. Davies 1 1 University of Lancaster, Institute of Environmental and Biological Sciences, Lancaster, LA14YQ, and 2 Neoplants Ltd., Freckleton, Lancashire, PR4 1HU, U.K. Introduction suggested that a reduced exposure to fog- ging treatment resulted in reduced plant loss and therefore experiments were Weaning of plantlets produced in micro- conducted where the effects of different propagation often requires an extended weaning conditions on structure and phy- period of growth in a fogging facility. This siology of leaves were investigated. treatment reduces the risk of damage due to desiccation when plantlets are removed from culture. Desiccation injury is a parti- cular problem because of limited develop- Materials and Methods ment of cuticle, abnormal stomatal behav- iour and abnormal xylem development in On 3 different occasions, transfer- plants were plants raised by these techniques. While red from culture to a peat-based compost effects of culture conditions are generally contained in modular trays. These trays were well understood, much less attention has placed in the fogging house for 7 d or 21 d be- fore they were moved to the greenhouse. been directed at any morphological and Plants were: a) ’fogged’ in autumn 1987; b) physiological lesions induced by condi- ’fogged’ in early summer 1988; c) ’fogged’ in tions employed during weaning. late summer 1988. Greenhouse conditions for plants from groups a and c were generally cool Photinia fraseri Red Robin is an ever- and humid, while plants in group b were ex- green woody shrub prized for its bright red posed to hot and dry conditions. young foliage. This plant can be multiplied Samples of fresh leaf tissue were taken and successfully in culture and will root effec- frozen in slushy nitrogen prior to examination tively in compost shortly after transfer from under the scanning electron microscope (SEM). a rooting medium. Problems were ob- Material was prepared on the freezing stage of the Joel JSM 840A microscope, coated with served initially with plants that had been in gold and examined at 8 kV. a fogging house for 20 d. Older leaves of Gas exchange of single leaves was moni- well-rooted plants became flaccid, follow- tored in a system similar to that described by ed rapidly by browning and death of the Atkinson, (1986). All measurements were made whole plant. No pathological symptoms on young fully expanded leaves that had been were detected. Preliminary observations initiated and had expanded at least partly in the
nation of the abaxial surface of leaves of fog-house. Experimental conditions were: leaf temperatures 23°C, 0 21 %, PAR 1000 ymol 2 plants from group a showed that 7 d fog- M and Aw 10 mmol mol- CO assimila- , 12 , 1 S 2 - ging resulted in apparently normal leaf tion rate (A) was measured at various ambient development, white plants that had re- P and NC (intercellular C0 concentra- 2 ¡ ) 2 (C0 ceived 21 d fogging showed abnormal sto- tion) analysis was performed (Farquhar and Sharkey, 1982). Plants examined using the matal development (Fig. 1 ’Normal’ ). above techniques were of a comparable age leaves had a stomatal density of approxi- (i.e., 7 d fog + 21 d in geenhouse or 21 d fog mately 50 mm- while extended fogging , 2 and 7 d in greenhouse). resulted in the normal development of less than half this number of stomata. Pores failed to develop between the guard cells Results of the other stomata. Examination of leaves from group c plants revealed that many developing leaves also showed very There was a high mortality rate of plants restricted stom;atal development. from group a that had received 21 d fog, Extended fogging of group b plants while many plants from group c that had reduced stomatal conductance (g) and received 7 d fog also died. Plants from both assimilation rate (A) and transpiration group b showed very low mortality. Exami-
followed by cool and damp conditions in (E) (Table I). AlC analysis showed that I the greenhouse (group c) greatly restrict- extended fogging at high temperature ed stomatal conductance and gas ex- increased the stomatal limitation of photo- change and this was apparently due to synthesis (results not shown). Group c restricted stomatal development. G was plants showed very low stomatal conduc- close to the C0 compensation point and 2 tances and rates of gas exchange (Table this would be expected to enhance photo- I). Intercellular C0 concentration was 2 respiration rates with adverse effects on very low and C of these plants was a lC i the capacity for carbon gain and success- approximately 60% of that found for most ful growth and development. C plants (Wong et al., 1979). 3 of low suggested that a combination It is temperature and extended fogging allows only restricted stomatal development. This Discussion and Conclusion restricts C0 uptake such that carbon gain 2 eventually proves inadequate to sustain growth and development. Extended fogging of Photinia plants at cool temperatures resulted in high mortali- ty rates (group a). These plants showed only limited stomatal development (see References Fig. 1) which might be expected to restrict gas exchange. Plants fogged for extended higher temperatures (group b) periods at Mooney M.A. Atkinson C.J., Winner W.E. & showed restricted rates of photosynthesis (1986) A field-portable exchange system for measuring carbon dioxide and water vapour due to enhanced stomatal limitations but exchange rates of leaves during fumigation with this reduction was not substantial. Inter- S0 Plant Cell Environ. 9, 711-719 9 - 2 estingly, plants in this group showed very G.D. & Sharkey T.D. (1982) Stomatal Farquhar low mortality rates even when fogged for conductance and photosynthesis. Annu. Rev. 21 d. We have not examined leaves of Plant Physiol. 33, 317-345 these plants under the SEM but it seems Wong S.C., Cowan LR. & Farquhar G.D. (1979) likely that they have developed relatively Stomatal conductance correlates with photo- synthetic capacity. Nature 282, 424-426 normally. Fogging at lower temperatures