Pomology
Masud Fattahi; Shirin Pourmoghadam
Abstract
Introduction
Almond (Prunus amygdalus) is considered to be able to tolerate drought stress fairly well during all stages of growth. Water shortages are very frequent in many countries, and, together with the rising demand for the industry, the growth of the human population, climate change and ...
Read More
Introduction
Almond (Prunus amygdalus) is considered to be able to tolerate drought stress fairly well during all stages of growth. Water shortages are very frequent in many countries, and, together with the rising demand for the industry, the growth of the human population, climate change and specifically the trend towards irrigated agriculture, have led to widespread problems of water scarcity in most countries. Plant responses to water deprivation are usually monitored through selected morphological and physiological parameters which have been proven to be good indicators of drought in different studies. Chlorophyll a (Chl a) fluorescence, produced by the Chl a molecule after excitation by light, is a non-invasive and rapid biomarker for the assessment of stress (microbial and environmental) effects on PSII, as well as its structure and function. Fluorescence induction patterns and derived indices have been used as empirical diagnostic tools in stress physiology. The aim of this study was to investigate the effect of water stress on chlorophyll fluorescence parameters in two almond genotypes. It is known that the kinetics of fluorescence transients are polyphasic when plotted on a logarithmic time scale labeled as OJIP. This curve rises from an initial low-value F0 (minimal fluorescence) to FJ (fluorescence value at 2 ms) and FI (fluorescence value at about 20–30 ms) and a peak of fluorescence FP (maximal fluorescence or Fm).
Materials and Methods
The Experiment was carried out under a completely randomized design with split arrangement having three replications. Chlorophyll and carotenoid contents were determined by the method of Lichtenthaler (1986). Fresh leaves (1 g) were triturated in 80% acetone. The absorbance of the extracts was measured at 645, 663, and 470 nm using a spectrophotometer. Chlorophyll fluorescence was measured 40 days after the start of drought treatment. Full expanded leaves were selected from each plant for measurements. They were measured with a portable photosynthetic efficiency analyzer model (Hansatech, United Kingdom). Calculations were made with computer-assisted analysis using the SPSS 25 software.
Results and Discussion
The results showed that the maximum total fresh and dry mass was recorded in the Mamaei cultivar. The drought stress caused a significant reduction in a, b, total chlorophyll and carotenoids in Rabie (R) as well as Mamaei (M) cultivars but in general, M plants had higher content of pigments in comparison with R plants under drought stress. In both of cultivars, the potential efficiency of PSII photochemistry (Fv/Fm) was reduced with an increasing drought intensity. The reduction of Fv/Fm was accompanied by a decline in Fv and Fm. The VJ, relative variable fluorescence at J step (2 ms), was increased with increase in drought levels. Plants response to drought depends on PSII ability to respond to this stress. It has been reported that water limitation reduces the quantum yield of PSII electron transport, which in turn decreases the amount of light energy reaching the reaction centers. PSII plays a pivotal role in mediating oxygen evolution activity. In our study, we observed an interaction between cultivar and drought treatment, particularly evident in parameters such as Fm, Fv, Fv/Fm, and PI. Additionally, our findings revealed a robust correlation between the Pi index and total chlorophyll content (0.647), as well as the fresh (0.685) and dry (0.695) weight of plants. Furthermore, our results indicate that drought stress significantly impairs the growth of cultivars grafted on GN15 rootstock. This may be the outcome of the inhibition of water shortage on the photosynthetic apparatus. The results discovered that carotenoids were higher in M cultivar than R cultivar, carotenoids protect the photosynthetic apparatus from photooxidative damage. Protection is afforded by quenching of the triplet state of chlorophyll, thereby preventing the formation of harmful oxidative species. We also found the performance index is the parameter that better reflects the responses of the studied cultivars to progressive drought stress.
Conclusion
We applied chlorophyll fluorescence as a biomarker to assess the growth response and PSII behavior and performance of two almond cultivars to different drought levels. In conclusion, Mamaei was less affected by drought stress in terms of total Chl, Fv/Fm, PI, and total fresh and dry weight followed by Rabie. Differential responses among cultivars under drought stress treatments were observed regarding their capacity to induce PSII activity. Parameters derived from the JIP test proved effective in characterizing the degree of response to drought stress, with PI serving as a particularly responsive multi-parametric expression.
Pomology
Masud Fattahi; Abdolrahman Mohammadkhani
Abstract
Introduction
UCB-1 hybrid rootstock is propagated from the seed of a controlled cross between a P. atlantica female and a P. integerrima male. Clonal propagation of this rootstock is also necessary since it produces identical genotypes. UCB1 has recently been introduced in Iran. However, little ...
Read More
Introduction
UCB-1 hybrid rootstock is propagated from the seed of a controlled cross between a P. atlantica female and a P. integerrima male. Clonal propagation of this rootstock is also necessary since it produces identical genotypes. UCB1 has recently been introduced in Iran. However, little research has been done on this subject. Water stress is one of the most important environmental stresses and occurs for several reasons, including low rainfall, high and low temperatures, salinity, and high intensity of light, among others. Drought stress is a multidimensional stress and causes changes in the physiological, morphological, biochemical, and molecular traits in plants. Proline is also found widely in plants and accumulates in large quantities in response to environmental stresses such as drought. It is the essential amino acids that accumulate in different tissues of the plant, especially in the leaves through the effect of water stress, and that the accumulation of it has a function in the regulation of osmosis in the cell as the proline is increased in the cytoplasm to counterbalance effort osmosis cell sap. Proline is an indicator of water stress tolerance and its increase in the leaf proof that the plant suffered drought stress, also is the way the plant tolerance to drought stress.
Materials and Methods
A pot experiment was conducted, to investigate the effectiveness of foliar applied proline in mitigating the concurrent effects of drought stresses on UCB1 rootstock, at greenhouse of Faculty of Agriculture, University of Shahrekord. Experiment was carried out in a completely randomized design with split arrangement having three replications. Chl. and carotenoid contents were determined according to Lichtenthaler (1987). Leaf discs were obtained from expanded leaves of each pot in the morning. The leaf discs were weighed immediately to obtain the fresh weight (FW), and submerged in distilled water for 4 h at 4◦C in dark condition and then weighed to prepare turgor weight (TW). The leaves were dried in a forced-air oven at 70◦C for 24 h, and the dry weight (DW) was recorded. The RWC of samples was calculated using the following equation (Bastam et al., 2012): RWC = [(FW–DW)/(TW–DW)] × 100
Levels of glycine betaine were quantified as described previously by Arakawa et al. (1990). To determine the free-proline concentration, leaves were homogenized in 5 ml of ethanol at 95%. Proline concentration was calculated with a standard curve and expressed as µg g−1fresh mass (Paquin and Lechasseur, 1979).
Results and Discussion
The UCB1 proximate analysis in the present study depicted that imposition of drought stress increased the leaf and root proline content and electrolyte leakage. Exogenous application of proline as foliar spray significantly increased the moisture content of leaf and root, RWC, Chl a and total chlorophyll. Exogenous proline application upregulated leaf and root proline contents and decreased the lipid peroxidation (decrease electrolyte leakage), resulting into improvement in chlorophyll contents. 150 mg. l-1 proline application gave maximum alleviation against stress.
Numerous reports depict that the exogenous application of proline as a foliar spray can play an important role in enhancing plant tolerance against drought stress, and our results are consistent with them. This ameliorating effect of exogenously applied proline can take the form of osmoprotection, cryoprotection, or protection against reactive oxygen species.For example, in various plant species growing under stress conditions, exogenously supplied proline provided osmoprotection and facilitated plant growth. Normally, proline accumulation in plants, is in response to drought or salinity stress occurs in the cytosol where it contributes substantially to the cytoplasmic osmotic adjustment. It actively takes part in plant osmotic adjustment under stressful environmental conditions. In addition to its role as an osmolyte for osmotic adjustment, it actively takes part to stabilize subcellular structures, biological membranes, proteins, and scavenge free radicals. It also plays a vital role in buffering cellular redox potential under stressful environmental conditions.
Conclusion
In summary, our results showed that, drought induces a decrease in moisture content, RWC, T Chl and carotenoids and an increase in some osmoregulators (proline, glycine betaine, TSC). The most favorable treatment was 150 mg.l-1 proline foliar spray. 150 mg.l-1 proline application gave maximum alleviation against stress. Foliar application increased the moisture content of leaf and root, as well as increased the Chl a, total, RWC and proline content of leaf and root. It can be suggested that the foliar application of proline (150 mg L-1) used as a plants defense factor against drought stress conditions.
Masud Fattahi; Abdorahman Mohammadkhani
Abstract
Introduction: Abiotic stresses, in particular drought, not only compromise crop quality and limit yield, but also restrict the geographical range over which crop production is viable. Plant species have evolved a number of physiological and molecular means to cope with adverse environmental conditions. ...
Read More
Introduction: Abiotic stresses, in particular drought, not only compromise crop quality and limit yield, but also restrict the geographical range over which crop production is viable. Plant species have evolved a number of physiological and molecular means to cope with adverse environmental conditions. Grapevine is a perennial crop grown in various areas around the world. It is highly responsive to local environmental conditions and viticultural practices. Abiotic stresses cause extensive losses to agricultural productivity. Grapevine is no exception to the rule and faces several abiotic stresses throughout its lifespan. Drought, salinity, or heavy metals are serious problems in many parts of the world. The potential of AMF to enhance plant tolerance to abiotic stress conditions has long been known, and their use in sustainable agricultural systems will be of tremendous importance for soil quality and crop productivity under severe edapho-climatic conditions. Arbuscular mycorrhizal fungi (AMF), a kind of beneficial soil microorganism, can create a symbiotic association with plant roots forming arbuscular mycorrhizas (AMs), which play a role in the regulation of plant growth. This research was carried out in order to determine the effect of deficit irrigation on morphological characteristics of grapevine ʽAsgariʼ cultivar in greenhouse conditions in 2016.
Materials and Methods: The layout was as a factorial experiment in a completely randomized design with three replication and two factors, including Arbuscular mycorrhizal and irrigation regimes. Irrigation treatments were irrigation with 100% moisture content of field capacity (control), 70% moisture content between field capacity and permanent wilting point (MAD 30) and 40% moisture content between field capacity and permanent wilting point (MAD 60) and mycorrhizal treatments was including non-use of mycorrhizal and use of Glomus mosseae, G. intraradices, G. etunicatum and G. verciform. Some morphological traits including height, root length, root volume and root density, fresh and dry weight of leaf, stem and root, leaf area, number of leaf damage, leaf area, leaf diameter and symbiosis percent of grape roots with fungi were measured.
Results and Discussion: The results showed that mycorrhizal and 100% irrigation treatments increased the fresh and dry weight of leaf, stem and root, leaf area and the percentage of mycorrhizal symbiosis. Due to irrigation, the indices measured in the experiment such as height, fresh and dry weight of root, leaf and stem decreased, so that the decrease in without mycorrhizal plants was more than the with mycorrhizal plants. Generally, the use of mycorrhiza in this research has reduced the damaging effects of water stress on the morphological characteristics of grapevine, which in between the G. verciform and G. etunicatum were better than the G. mosseae and G. intraradices.
Conclusion: Grapevine phosphorus deficiency is usually rarely observed, not only mainly because of limited phosphorus requirement, but also because of sufficient phosphorus richness in the majority of vineyard soils and remobilization from bark, wood, and roots during periods of high P demand. Nevertheless, P deficiency have been described in vineyards in Australia, France, Germany and USA. Phosphorus deficiency symptoms correspond to stunt shoot growth, decrease in dry matter, and berry clusters.
Mycorrhizal treatments helped in alleviation of drought stresses. Enhanced uptake and storage of P, beyond what is required for immediate vegetative growth may be of particular importance for heavily pruned crops like grapes, since most of the new shoot growth is removed every year. These results were achieved in the greenhouse under almost controlled conditions and can be difficult to suggest for applying in the field conditions. Such experiments may be organized in the field conditions.
Present-day vineyard practices place several constraints on the use of functions provided by mycorrhiza. The risk of large, costly, or irreversible changes is to be reduced or averted. Future (modern) agriculture should be based on the implementation of ecological management practices that deliberately maintain resilience of ecosystem services. This means integrating the development of vineyard management strategies that optimize the impact of beneficial microbes like mycorrhizal fungi on production. Furthermore, AMF vary in their ability to provide ecological services so that suitable tools have to be defined to fully assess their contribution. Molecular tools have considerably improved the possibility to identify and monitor mycorrhizal fungi in ecosystems, but a quick and reliable test for assessing their functionality is still lacking. For producers’ expectations to be met, a novel industry encompassing soil/mycorrhiza analyses and advice to producers/managers is needed. Additional barriers to rationally exploiting beneficial soil microbes like mycorrhizal fungi as ecosystem services range from economical, technical, and cultural aspects to legislative questions. In spite of this, considerable progress has been made in the last decade for crop plants in general, but also for grapevine, towards the use of AMF.
