Báo cáo lâm nghiệp: development of winter hardiness of pine and spruce seedlings in a simulated acid rain experimen

Tuyển tập các báo cáo nghiên cứu về lâm nghiệp được đăng trên tạp chí lâm nghiệp Original article đề tài:development of winter hardiness of pine and spruce seedlings in a simulated acid rain experiment...
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Báo cáo lâm nghiệp: "development of winter hardiness of pine and spruce seedlings in a simulated acid rain experimen" development of winter hardiness of pine and spruceTheseedlings in a simulated acid rain experiment S. HuttunenJ. ReinikainenDepartment of Botany, University of Oulu, SF-90570 Oulu, FinlandIntroduction ResultsThe effects of acidified rainwater on the had alrea- of the The hardening seedlingshardiness level perceivable in the ultra- dy begun in mid-August, with decreasingstructure of needles of conifer seedlings numbers of starch grains and chloroplastswere examined during autumn and winter moving towards cell corners (Fig. 1The1986-87. needles of the northernmost provenances of spruce seedlings lost their starch grainsMaterials and MethodsOne and 2 yr old Scots pine (Pinus sylvestris)and Norway spruce (Picea abies) seedlingsfrom several provenances had been irrigatedwith artificially acidified rain (H 2:1) , 3 :HN0 4 S0 2for 7 wk during the hardening time in the pre-vious autumn. In the experiment performed atthe University of Oulu, the seedlings investigat-ed comprised samples treated with pH 3, pH 4and clean (pH about 7) water, in addition to adry control, with samples of each group from 2different provenances. The development of thehardiness level was followed by making lightand electron microscope observations of themesophyll tissue of the current year’s needles.Sampling was done about once a month fromAugust until April. The 0.5 mm thick needle cut-tings were fixed with glutaraldehyde and O 4 0 Sin 0.05 or 0.1 M phosphate buffer and, afterfixation, the needle sections were dehydrated inan alcohol series and embedded in Ladd’sepon. significantly affect the ultrastructure of the needles during the first winter. Discussion and Conclusion The deleterious effects of air pollutants on the cold tolerance of conifers have been reported quite recently by several authors (e.g., Davison and Barnes, 1986; Freer- Smith and Mansfield, 1987). However, the effects of acid rain on conifer seedlings could not be seen in the hardening pro- cess after 2 months’ exposure. Our results clarify the development of cold hardiness at the ultrastructural level. The hardening began in mid--August and the maximumearlier than the southernmost seedlings,whereas in pine seedlings no great differ-ences could be seen in this respect. InSeptember, the cytoplasm became net-like upon the increase of the endoplasmicreticulum (Fig. 2). During August-October,many small vacuoles containing granularmaterial developed in the cytoplasm. Myelin-like membranous formations inthe cytoplasm became abundant duringthe winter period (Fig. 3). As of Septem-ber, small, single-membrane fragments in the membrane-free areas ofwere seenthe chloroplasts. The highest incidence ofthese was noted in March-April, whenalso large, whorl-like membranous struc-tures were seen in abundance in chloro-plast stromata. Chloroplast division wasgreatest in September-October, butthroughout the winter some dividing chlo-roplasts could be seen. The mesophyllcells started to revert from the hardened tothe unhardened state in March-April,when the starch grains again appeared(Fig. 4). The exposure to acid rain did not to accumulate in chloroplasts. The devel- opment of freezing injury in the acid a rain-treated co ...