جستجوی مقالات مرتبط با کلیدواژه « خشکی » در نشریات گروه « جنگلداری »

The effects of ecological factors and their interaction on quantitative changes of 10 physiological, 12 anatomical and two morphological traits of leaves in six different populations of Caucasian alder (Alnus subcordata C.A.Mey.) in the west (Guilan province) and east (Golestan province) of Hyrcanian forests were examined and statistically compared in three altitudinal ranges of lowlands, midlands and highlands. Two-way analysis of variance was used to investigate the effect of ecological factors in the region (temperature and precipitation) and their interaction on the studied variables. The principal component analysis (PCA) was used for the correlation between leaf traits and the relationship between environmental factors. The activity of catalase, peroxidase enzymes and proline were significantly different between the two provinces and showed an increasing trend from west to east. In addition, the amount of phenol in the site located in Golestan province was about 1.5 times that of Guilan province. There was no significant difference between the levels of superoxide dismutase activity and the amount of soluble sugar between the two provinces. Superoxide dismutase showed an increasing trend from lowlands to highlands, but the amount of soluble sugar increased from low altitudes to midlands and decreased in the highlands. There was no significant difference in the amount of chlorophylls a and b, total chlorophyll and carotenoids between the two provinces and at different altitudes, as well as the effects of the interaction of ecological factors on them. The most important morphological and anatomical adaptations to drought included increased leaf thickness, stomata density and length, abaxial cuticle thickness, epidermal cell thickness, thickness of palisade cells, thickness of spongy cells, middle vein thickness, thickness of vein abaxial parenchyma cells and number of abaxial parenchyma layers of vein. There was a correlation between most leaf physiological as well as morphological traits and ecological factors. The results of analysis of variance and the interaction of ecological factors on some anatomical features of Caucasian alder leaves were significant. It seems that the anatomical adaptations that are formed in plants over a long period of time are more appropriate indicators for measuring drought stress in plants.

Cupressus sempervirens var. horizontalis, an ornamental tree, is suitable for wind break, soil conservation, wood production and forms a large part of seedling production in nurseries of Iran. Considering the expected limitations of water resources, the target of this investigation was to study the effect of rhizobacteria Pseudomonas fluorescens on the growth and survival of C. sempervirens seedlings under water deficit. The experiment was carried out with four irrigation periods and two rhizobacteria levels (inoculation and non-inoculation) in a randomized complete block design with three replications. To determine the amount of irrigation water, the field capacity was calculated and the water deficit was given to the plant to the desired moisture content after weighing of the pots. The seedlings in severe water deficit (irrigation period of 12 days) had a survival rate of 95% and higher. Shoot growth and diameter growth were, respectively, reduced by 52.6% and 49.6% in 12-day irrigation compared to 3-day irrigation, but inoculation increased by 14.7% and 14.3% in them, respectively. Regardless of water deficit, root biomass in inoculated seedlings increased by 23.2% compared to the non-inoculated seedlings. Shoot biomass, total biomass and seedling quality index in the period of 9 and 12 days and root volume during the 12-day period decreased, but by inoculation, these variables increased 13.9, 16.8, 20.1 and 25.3, respectively. Overall, although water deficit decreased growth characteristics of C. sempervirens seedlings but it can be concluded that root inoculation with P. fluorescens can be used as a biologic fertilizer to suit the growth and morphological quality of seedlings, even under severe water deficit conditions. This strategy can be useful for producing proper seedlings of C. sempervirens in nurseries facing water constraints.

Osage orange tree (Maclura pomifera L.) is a native of Central America and has numerous ornamental, ecological and medicinal values. In the present study, the effects of different culture media including animal manure, vermicompost and sesame residue on the growth rate and increasing tolerance of Osage orange tree under drought stress, were investigated. This experiment was conducted as a factorial experiment based on completely randomized block design, four culture media levels including (1- soil (control), 2- 70% v/v soil + 30% v/v vermicompost, 3- 70% v/v soil + 30% v/v animal manure and 4- 80% v/v soil + 20% v/v sesame residue) and three levels of drought include 1- without stress (control) (90% allowed water depletion) 2- mild stress (55% allowed water depletion) and 3- severe stress (35% allowed water depletion) with three replicates per treatments were applied on one year old seedlings in April 2017 in field of Yazd University. According to the results, drought stress significantly decreased the height, truck diameter, fresh and dry weight of leaves of seedlings and nutrient uptake, however, activity of ascorbate peroxidase increased. Application of a modified culture media under non-stress conditions significantly increased the growth characteristics and nitrogen and phosphorus uptake. Among the used culture media, animal manure and sesame residue had the highest effects on increasing plant height, fresh and dry weight of leaves and absorption of nitrogen and phosphorus. Maximum activity of ascorbate peroxidase enzyme was obtained in agronomic soil with 30% vermicompost during severe drought stress. In general, using the culture media, especially with animal manure and sesame residue, increased the resistance of this plant to drought stress and significantly increased its growth.

The effects of different irrigation regime on survival and growth of holm oak (Quercus ilex L.) plantationwas studied in a semi-arid Mediterranean climate condition located in Marzanabad region (Mazindaran province). This study was done as Randomized Complete Block design with three replicates and four treatments, including no-irrigation and irrigation with 10, 20 and 30 day periods during dry months in growing seasons (spring and summer). Climate data analysis showed that a severe frost and three to six dry months annually occurred in growing season during study years (2006-2010). Height growth and survival of saplings were measured every year and at the end of 5th year. Analysis of data showed that irrigation treatment with 10-day intervals with a 65% survival is preferred and differences are significant (p %1). No difference was seen among treatments from height growth point of view. In general, the most important restricting factor on holm oak establishment and growth in this area are alkaline soil and dry environment conditions.