جستجوی مقالات مرتبط با کلیدواژه « water stress » در نشریات گروه « جنگلداری »

The mechanical characteristics of roots can serve as a significant factor for selecting trees in the plantation of arid regions for soil bioengineering. This research aims to evaluate the mechanical characteristics of Tehran pine roots at various vegetative ages (one-year-old, three-year-old, and five-year-old seedlings) and under different water stress levels (light, medium, and severe) in Robat Karim. The mechanical properties of the roots were studied after estimating the water requirement of the studied seedlings at different ages for one year and based on the water stress levels. Then, five seedlings from each treatment (equal to 9 treatments) were selected and coded completely randomly to evaluate the water stress on the mechanical characteristics of the roots of Tehran pine. Initially, some root parameters such as root diameter, length of the whole root, length of thin roots, and length of the longest root were measured. Then the tensile force, tensile strength, and Young's modulus of the roots were measured and recorded using a standard Centam device. The results showed that with the increase in root diameter, the tensile force of the root changes based on the positive power relationship, and the tensile strength and Young's modulus of the root changes based on the negative power relationship. Furthermore, laboratory examinations showed that at any age, the length of the whole root and the root length densities are higher with the increase in water stress. The use of covariance analysis showed that the results of the average comparison between one-year-old age and mild drought stress, three-year-old age and moderate stress, and five-year-old age and severe stress are significant with a probability of 95%. The results of this research show that the mechanical characteristics of the root can be used as an important factor for the selection of pine seedlings in the afforestation of arid areas for soil bioengineering purposes. Therefore, it is recommended that these properties be considered in soil reinforcement modeling.

The use of biofertilizers such as plant growth-promoting bacteria to reduce damage caused by water-deficit stress in plants and improve physiological factors and thus increase plant growth in arid and semi-arid regions is an essential management to control water-deficit stress. Therefore, this study was conducted to investigate the simultaneous effect of different levels of water-deficit stress and inoculation of plant growth-promoting bacteria on some physiological traits of Brant's Oak )Quercus brantii L.) seedlings.

In order to investigate the effect of plant growth-promoting bacteria and different levels of irrigation on some physiological traits of oak) Quercus brantii L.) seedlings, an experiment was conducted in a complete randomized design with five replications in the research greenhouse of Yazd University. The main factor was three irrigation levels (80 % of full irrigation as control, 60 and 40 % of full irrigation) and the sub-factor was six levels of plant growth promoting bacteria (no inoculation as control and seed inoculation with Bacillus anthracis, B. licheniformis, Stenotrophomonas maltophilia, B. cereus and BMix (combination of 4 strains().

The results of analysis of variance showed a significant effect of water deficit stress levels, bacterial treatments and their interaction on all studied traits. The results of comparison of means showed that the amount of chlorophyll a, b and total chlorophyll decreases with increasing levels of water-deficit. In contrast, the amount of proline, total phenol and percentage of free radical scavenging in oak seedlings under stress increased significantly compared to the control sample. The accumulation of malondialdehyde (MDA) that shows the rate of degradation and peroxidation of membrane lipids were significantly increased by water-deficit treatments, while application of PGPRs caused reduction in malondialdehyde content. These results showed that PGPRs can reduce negative effects on lipids peroxidation and thus increases the resistance of seedlings to water-deficit stress conditions.

In general, among the bacterial treatments, (BMix) bacterial treatment increased chlorophyll a and b, total chlorophyll and decreased malondialdehyde and Bacillus anthracis bacterial treatment increased proline, total phenol and percentage of free radical scavenging under water-deficit severe stress.

Judas tree (Cercis siliquastrum L.) is a suitable species for improving the soil nitrogen fixation and creating the natural landscape in parks and roadsides. This study was aimed to investigate the growth, development and drought resistance of Cercis seedlings by applying different irrigation periods. First, the seeds of Cercis were treated to germinate and reach to seedling phase (30 cm in height) for 90 days. Then, the seedlings were examined in a completely randomized design with four irrigation periods (4, 8, 12, and 16 days) and three replicates for 70 days. Irrigation significantly affected all morphological characters whereas stem length, root length, specific leaf area, shoot dry mass, leaf dry mass (p≤ 5%) and other characters (p≤ 1%) were different among the irrigation periods. The highest stem length, collar diameter, leaf number, leaf area, shoot dry mass, leaf dry mass, collar diameter growth, height growth and survival rate were observed in 4-day irrigation period. Seedlings with 8-day irrigation period had the greatest root volume, root dry mass and plant dry mass. This is while that, the 8-day irrigation period induced the greatest root length, specific leaf area and root/shoot ratio. The results revealed that the 4-day irrigation period was suitable for raising the Cercis seedlings; however, due to the satisfactory survival and growth, as well as the low cost and easy maintenance of seedlings, the 8-day irrigation period can be a good alternative for seedling production of this species.

The investigation was conducted at two trials. At the first trial, genotypes number one (G1) and two (G2) of the cultivated almond (Prunus dulcis var. amara) with seed origin from Esfahan-Najafabad and one ecotype (E1) of the natural almond (Amygdalus scoparia) with seed origin from Esfahan-Semirom) were tested under the Statistical Design of Split Plots, with three replicates. The main treatments were five soil water contents (7, 10, 13, 16 and 20 percent) and the second treatments were the almond ecotype and genotypes. The second trial was similar to the first one at the main treatments but different at the second treatments. The second treatments were as follows:  - Three almond cultivated genotypes: G4, G5, and G6 - One almond native ecotype (E2) with seed origin from Kurdestan-Paveh. The measured seedlings quantitative and physiological characteristics were as follows: stem height (SH), stem collar diameter (SCD), leaves dry weight (LDW), stem dry weight (SDW), root dry weight (RDW), leaf thickness, leaf total number (LTN) and branch numbers (BN), leaf proline rate (LPR), and leaf stomata (LS). The first trial showed that although there was significant difference between E1, and G1, G2, through the seedlings SH, LDW, SDW, RDW, SCD and LN characteristics, but the G1 was the most resistant Almond to water stress. The almond genotype resistance was due to its high root volume, which resulted in high shoot volume as well. The second trial showed that there were significant difference between E2 and G4, G5, G6 through the seedlings SH, RDW and LN characteristics. G6 had the highest and E2 and G5 had the lowest root volume. Overall, there were greater differences between the Almond species and genotypes in root dry weight than in shoot dry weight. G6 and G4 were the most resistant to water stress, respectively.