جستجوی مقالات مرتبط با کلیدواژه "chlorophyll a" در نشریات گروه "جنگلداری"

To investigate the effect of drought stress on the vegetative, physiological, and biochemical characteristics of purple seedlings, an experiment was conducted in the form of a completely randomized design with four levels of irrigation including 75% (mild stress), 50% (medium stress) and 25% (severe stress) of the field capacity (FC) and the control (100% FC) in greenhouse conditions. The results showed that severe drought stress significantly reduced vegetative traits such as seedling height growth (86.8%), the number of leaves, and total fresh and dry biomass by 93%, 46.2%, and 44.8%, respectively, but increased root volumetric growth (1034%). Also, drought stress affected all parameters of gas exchange and photosynthetic pigments. So that at the level of 25% FC, it caused a significant decrease in the rate of photosynthesis (1/20 µmolCo2m-2s-1), transpiration (0/65 mmolm-2s-1), stomatal conductance (106/2 mmolm-2s-1) and mesophilic (0/0088 mmolm-2s-1), intracellular carbon dioxide concentration (134/2 mmolCO2 m-2s-1) and carboxylation efficiency (0/00112 µmolCO2 mol-1H2O). The amount of photosynthetic pigments (chlorophyll a, b, total chlorophyll, and carotenoids) also showed a significant decrease at 25% FC (4.07, 1.96, 6.03 and 1.23 mg g-1 FW, respectively.). Also, drought stress increased the amount of proline and soluble sugar and showed the highest values at the level of 25% FC (respectively, 1.348 µmol g-1 FW of proline and 41.51 mg g-1 FW of soluble sugar). According to the above evaluations, it seems that the purple variety can tolerate drought stress up to 75% FC without causing damage to the plant tissue, but if the amount of water is reduced to the threshold of 25% FC, its growth and performance will be severely affected.

The regeneration of trees in forests with a long dry season such as Zagros has extreme difficulties. Predicting of water deficit tolerance in the progenies based on the geographic, vegetative and physiologic characteristics such as the performance of photosystem can conducted to increasing the efficiency of plantations.

In this study, the progenies of 40 Persian oak trees derived from 8 populations located in southern Zagros forests were assessed for water deficit tolerance based on their geographic, growth and physiological characteristics such as photosystem II under greenhouse conditions. Also, the percentage of seedling establishment for each mother tree were evaluated by field trial during two years. The corresponding data obtained from these experiments in accompanied by the morphological characteristics of leaves and seeds of mother trees were used to developing of the predictive models of seedling establishment in the field. In this research, greenhouse and forest field experiment was conducted to evaluate the response of Persian oak seedlings to drought stress based on some indicators of stress resistance from photosystem II. Persian oak seedlings from different mother trees were subjected to drought stress by stopping irrigation for one month in the greenhouse conditions. Then, the seedlings were irrigated for one month again and in all stages, the photosystem II, the percentage of leaf yellowing and the percentage of survival of the seedlings were recorded. Also, the establishment of the offspring of mother trees in the forest field was evaluated based on the percentage of survival and the height of the seedlings during two years, and their relationship with the leaf and seed morphological characteristics of the mother trees was investigated.  

The results showed that there is a positive relationship between the percentage of survival, and stress resistance indicators in greenhouse conditions with the percentage of survival and the height of seedlings in the forest field. Also, seedlings from drier seed origin, lower altitudes and latitudes, had higher drought resistance in greenhouse conditions. However, none of the growth and survival parameters in the field was related to the environmental characteristics of population. The relationship between the leaf and seed morphological characteristics of mother trees with stress resistance and the establishment of seedlings showed that the seedlings grown from wider and heavier seeds had better growth characteristics and survival only in the first year. Also, some leaf morphological characteristics of mother trees, such as petiole length, tooth width and number of veins were affecting traits to seedlings successful establishment in the forest field.

The results of this research showed that collecting of larger seeds from mother trees with suitable leaf traits could be effective for reforestation success. In addition, the use of physiological traits in the control condition in greenhouse can help for selecting the resistant progenies from superior populations or mother trees.

The aim of this study was to measure the amount of dehydration stress in native trees in the middle of summer by comparing the three important enzymes response to this stress and photosynthetic pigments in the studied habitats. In order to carry out this research, four habitats in Guilan, Mazandaran and Golestan provinces were selected for sampling. From each region, 15 mother trees were selected. Peroxidase enzymes, catalase and ascorbate peroxidase and chlorophyll pigments including chlorophyll a, b, total and carotenoids were measured. The results of this study showed that Fagus populations in all regions had different antioxidant activity at the peak of drought stress in the middle of summer, so that the population of Shastkalateh with the least rainfall compared to other areas, had higher levels of peroxidase and ascorbate peroxidase enzymes. Also, all regions of the study had a different chlorophyll a content, so that the populations of Shastkalateh and then Up land kheyrood had the lowest chlorophyll content. The correlation results indicate a significant positive correlation between chlorophyll a and rainfall in the studied areas. Chlorophyll a, peroxidase enzymes and ascorbate peroxidase were also identified as effective and significant traits in response to drought stress in the studied areas.

Populous euramericana triplo is the most important wood production species in the north of Iran. According to climate change and limitation in water sources, the production of seedlings and establishment of this species has become particularly problematic in some of these sites including East of Mazandaran and Golestan regione under dryland conditions. Purpose of this study was conducted to identify drought tolerant Populous euramericana triplo seedlings under water stress. By using nanozeolite application in rhizospher soil, for the first time to different watering regimes to finding the best method and technique for production of seedling in nurseries and successful wood production. The aim of this investigation was evaluation of growth of one of poplar clone in water stress conditions.

In this study, 180 seedlings hybrid clone of Populous euramericana triplo were used so that healthy seedlings of uniform height were chosen for experiment of application nanozeolite treatment under drought stress (four watering regimes). The experiment was conducted as with two treatments (nanozeolite including, 0, 1% and 5% w/w), (0, 10, 50 g/kg soil) and different watering levels (3, 6, 9 and 12 dayes) nearly three month in growing season in Ghaemshahr Horticultural Research Station in green house so that the survival rate, growth and some morphological traits were investigated. Therefor the experiment was conducted as a factorial, using a randomized completely block design in green house condition with three replication.

The results of this study showed that triplo clone seedlings under drought treatment suffered significant water loss displayed decline in growth. So that increasing the watering period (water stress) caused to significantly decrease the survival percentages, diameter growth, height growth, morphological characteristics including, leaf number, leaf area, leaf biomass, shoot biomass, root biomass, root length, root volume and chlorophyll content. While, the mentioned growth parameters were greater in seedlings inoculated with adding 1% nanozeolite (10 g/kg soil), compared with those of non- application seedlings and it was the best effect on drought tolerance so that the seedlings in severe water stress (12 days of irrigation interval) had increased in these properties such as, height growth, leaf number, leaf area, leaf biomass, shoot biomass, root biomass were respectively increased by 50, 54, 155, 188, 40 and 47%.

In this study was demonstrated Populous euramericana triplo species was gentle derought tolerance and the addition of 1% nanozeolite for decrease of water stress on seedling and improving growth this species is suitable. Survival rate of seedlings were up to 80% in watering periods of 9 and 12 days. Thus, suggests that These irrigations interval for seedling production of hybrid clone populous in nurseries and establishment of Field. Moreover, in order to enhance of resistance of populous seedlings in drought conditions (watering regimes) for wood production and establishment of seedling hybrid clone populous nanozeolite application (1% w/w) could be used.

Among the different species of Pistacia genus, P. atlantica is more distributed in cold area than P. khinjuk. In this study, in order to illustrate the physiological mechanisms of cold tolerance under acclimation phenomenon, two experiments were established. First experiment was conducted to induction of acclimation on seedlings at two stages and each stage was done for two weeks with different photoperiods. Then chlorophyll and florescence's chlorophyll was measured. For second experiment, leaves and stems of seedlings were exposed to three levels of temperature, +4°C (control), -20°C in one hour and -20°C in two hours. For this purpose, we measure relative water content (RWC) and electrolyte leakage (EL). Results of first experiment showed that 44% electron transport rate and 46% photochemical quenching was significantly reduced. This reduction in P. atlantica was grater by 30% compared to P. khinjuk. Second experiment results revealed that leaf RWC and EL increased during cold acclimation to be 8 and 11%, respectively. In addition, stem EL increased only in P. khinjuk (44%). In fact, P. atlantica due to decreasing of RWC during acclimation was able to maintain the photosystem efficiency and showed more resistance to cold stress. According to our findings, we can identify cold-resistant species or genotypes by measuring the florescence's chlorophyll.

Physiological response of different species to drought stress can help to recognize the effective mechanisms in drought stress and choose the best species for planting in dry lands of Iran. This study investigated the physiological mechanisms of Robinia pseudoacacia L. seedlings in draught conditions. An experiment was carried out in a completely randomized block with one treatment (irrigation) at five levels (1, 3, 5, 7, and 9 -day intervals) with five replicates in one-year-old seedlings of Robinia pseudoacacia L. The effects of drought stress, chlorophyll fluorescence parameters (Fv/Fm, Fm & F0), pigments concentrate (total chlorophyle, chlorophyle ‘a’ and ‘b’), and proline content of leaves were measured with sampling from leaves of mentioned treatments. Drought stress caused a significant reduction in maximum photochemical efficiency of photosystem II (Fv/Fm), maximum fluorescence (Fm) and minimum fluorescence (F0) (p

This study was investigated the gas exchange parameters and Chlorophyll fluorescence yield in Iranian oak (Quercus macranthera F & M) seedling under drought stress in Golestan Province. For this aims, 2 years old of Iranian oak exposed (Quercus macranthera F & M) seedling from Golestan province population exposed to three soil moisture regimes (control, any drought stress (95% field capacity), medium drought stress (60% field capacity) and severe drought stress (% 25 FC) for 45 days’. The gas exchange parameters, water relations and chlorophyll fluorescence were measured. The results showed that photosynthesis, transpiration, stomatal conductance, Fv/Fm, YII and water potential of severe drought stress treatment after 15 days were significantly lesser compared to control treatment. In general Iranian Oak seeding after 15 days in order to avoid of water desiccation in severe drought treatment decreased the gas exchange parameters (photosynthesis, transpiration, stomatal conductance) chlorophyll fluorescence (Fv/Fm and YII) in compare with control treatment. Also using of tolerance water desiccation strategy by Q.macranthera led to after 30 and 45 days, the gas exchange parameters (photosynthesis, transpiration, stomatal conductance) and chlorophyll florescence fluorescence (Fv/Fm and YII) of severe drought treatment hasn’t change compare to its 15 days. According to our findings, it can be concluded Iranian Oak call successfully pass the drought stress using avoidance and tolerance strtegies.

It is of crucial importance to assess the performance of the photosystem II efficiency, as the most powerful system in light reactions of photosynthesis that is able to provide required electron of system by splitting water. Late frost occurred mostly in growing season and during night in early spring often results in weakness and even death of plants. Therefore, selecting tolerant varieties is one of the most efficient methods to deal with late frost. Due to high diversity and wide dispersal, poplars significantly contribute to the worldwide supply of cellulosic resources. In order to investigate the effect of night late frost on functional component of photosystem II and a number of related physiological traits, seedlings of three clones of black poplar (Populus nigra L.) were exposed to the minimum night temperature of 16, 4, 0 and –20 °C for three nights. To assess the revival potential, seedlings were further maintained in optimum temperature for 14 days. Data were analyzed using a factorial model with two factors of clone and minimum night temperature for each step of the stress and revival. Results revealed that maximum and quantum yield efficiency of photosystem II in different clones has different reduction patterns according to the efficiency of water splitting complex and plastoquinon pool (PQ). Thus, Iranian clone was concluded to be more sensitive than other clones. This difference was discussed in association with total soluble sugar, proline and chlorophyll concentration and electrolyte leakage rate of cytoplasmic membrane. In addition, the recovery process of the clones in revival period was discussed.

Drought stress is one of the most important environmental factors limiting plant growth and development so finding the new techniques to evaluate the drought tolerance in plants, would be valuable. The purpose of this study was the application of chlorophyll fluorescence technique as a reliable method for rapid assessment of drought stress in hackberry seedlings (Celtis caucasica L.). An experiment was designed as completely randomized block with one factor (irrigation), at five levels (1, 3, 5, 7 and 9 days) with five replicates. Chlorophyll fluorescence parameters (Fv/Fm, Fm & F0), and the proline content of leaves in one-year-old seedlings of Celtis caucasica were measured. The results indicated that maximum fluorescence (Fm) had a significant reduction in the 9 days treatment. Also maximum photochemical efficiency of photosystem II (Fv/Fm) showed a significant downward trend since the 5 days treatment, while the minimum fluorescence (F0) was not significantly affected by drought. Increasing the intensity of drought was resulted in proline accumulation in leaves from 1.7 (µmol/gfw) in the 1 day treatment to 72.95 in the 9 days treatment. In afforestations and urban green spaces, measurement of chlorophyll fluorescence is a reliable method for identification of well-adapted species to environmental stress.

Remote sensing systems especially hyperspectral remote sensing for recognizing tree species and mapping forest type requires fundamental knowledge of spectral reflectance of desired tree species. A field of remote sensing named field spectrometry dealing with determination of these spectral characteristics tries to provide the spectral libraries for different objects. The main objective of this study was to prepare the spectral signature of the most important forest tree species of the northern forests of Iran. With this respect for the first time, field Spectroradiometric measurements were carried out using a full range spectrometer with Wageningen University of the Netherlands corporation during the summer 2007. The spectral fingerprint of five tree species namely Fagus orientalis, Quercus castaneifolia, Carpinus betulus, Alnus subcordata and Parrotia persica located in the Experimental Forest of Tehran University was prepared. A total of 321 leaf pile spectral curves were acquired of 107 trees of the mentioned species in altitude gradients between 400m and 2100m under clear and cloudless sky. A total of 100 scan for each leaf pile sample have been performed and averaged. After quality control and noises remove, the spectral fingerprint of the species was prepared along 350-2500nm. In order to investigate the spectral reflectance differences, five important vegetation indices related to leaf chlorophyll content were calculated and statistically analyzed. We conclude that the Vogelmann index and Simple Ratio is more sensitive to chlorophyll content in comparison to the other indices. It shows that hornbeam is significantly different in spectral signatures compared to beech, oak, and alder as well as ironwood with alder and oak being statistically different (p<0.0001, α= 0.01). For further investigation of spectral reflectance differences, we propose to make a correlation with extracted chlorophyll content and investigate the suitable vegetation indices related to other biochemical constituents and water content.