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ABSTRACT:To evaluate the effects of nano priming on seed germination of Alnus subcordata (Caucasian alder) C.A. von Meyer under drought stress, the present research was conducted using multi-walled carbon nanotubes (MWCNTs; 0, 10, 30, 50, and 100 mg·l -1 ) at 6 levels of drought stress (0, -2, -4, -6, -8, and -10 bar) through a factorial experiment (5 priming levels with 4 replications). After priming, the seeds were placed into a germinator at 21°C. Results revealed that nano priming at the concentration of 100 mg·l -1 led to the highest germination rate and percentage at all levels of drought stress.Also, the highest values of seed vigour index and root and stem lengths and dry weights were observed at nano carbon treatment with 30 mg·l -1 . Considering the obtained results, it was concluded that nano priming could result in boosted resistance of Caucasian alder seeds against drought stress, so that the seed tolerance increased from -4 bar (without nano priming treatment, i.e. reference sample) to -8 bar upon applying 100 mg·l -1 nanotubes. Based on the results of the present research, it is suggested that the seed nano priming technique with MWCNTs can be applied in order to increase the seed and seedling tolerance of other members of the genus Alnus Miller.

Oriental beech (Fagus orientalis Lipsky) is the most important and valuable industrial wood species in the Hyrcanian forests in the north of Iran mainly used for furniture, veneer, composite, and papermaking industries. The present research was conducted in 2014 aimed at investigating the physicochemical changes of the felled oriental beech stumps over a 2–25 year period, and likewise the feasibility of using the given stumps as an alternative resource for wood pulp production. To do so, the effects of in-situ decay of beech stumps on their physical (wet and dry weights of wood, wet apparent density, and dry apparent density) and chemical (cellulose, hemicellulose, lignin, extractives, and total mass of carbohydrates) properties over a 2–25 year felling period were studied. The effects of the given decay period were also studied on the obtained Kraft pulp yield and Kappa number. The results indicate that the wet and dry apparent densities as well as the wet and dry weights of the wood samples decreased over the study period. Also, the results show that approximately 30% of the total mass of carbohydrates was degraded by the ambient fungi over the initial two years of felling, whereas the same property was reduced by 60% after 25 years. The Kraft pulp yields obtained from 2- and 25-year decayed stumps were 22.5% and 8.4%, respectively. The fungal degradation of wood chemical compounds could considerably reduce pulp yield and Kappa number by 62.8% and 74.2%, respectively. The results of a stepwise  multivariate regression model evidence that cellulose not only affects the Kappa number but also owns a greater share (vs. lignin) in modelling the Kappa number. This reveals that the intensity of cellulose degradation, due to fungal exposure, is significantly higher than that of the other components of beech stumps in the studied forest area.

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