A hydroponic experiment was conducted to evaluate the role of potassium (K) in tomato plant growth exposed to cadmium (Cd) stress. In this work, the effects of three potassium nutrition regimes (155, ...232 and 310 ppm of K) combined with Cd at different levels (0, 12 and 25 µM of CdCl
) on chlorophyll content index, root and shoot dry weights, root morphology, chlorophyll a fluorescence and translocation factor were analyzed. The results showed a negative effect of cadmium, at different concentrations, on all these parameters. However, optimization of K nutrition has shown promising results by limiting the negative effect of Cd. A positive effect of the high concentration of K (310 ppm) was observed on leaf chlorophyll content and chlorophyll a fluorescence compared to 232 and 155 ppm under Cd stress. K supply improved the electron transport at PSI side indicated by the increase in the amplitude of the I-P phase of OJIP transient. Also, K at a concentration of 310 ppm significantly reduced Cd translocation from root to shoot and improved root and shoot growth parameters in the presence of Cd. K supplementation can reduce the negative effect of Cd by improving photosynthesis and promoting chlorophyll synthesis. The optimization of nutrients composition and concentration might be a good strategy to reduce the impact of Cd on plant growth and physiology.
Water shortage and soil nutrient depletion are considered the main factors limiting crops productivity in the Mediterranean region characterized by longer and frequent drought episodes. In this ...study, we investigated the interactive effects of P fertilizer form and soil moisture conditions on chickpea photosynthetic activity, water and nutrient uptake, and their consequent effects on biomass accumulation and nutrient use efficiency. Two P fertilizer formulas based on orthophosphates (Ortho-P) and polyphosphates (Poly-P) were evaluated under three irrigation regimes (I1: 75% of field capacity, I2: 50% FC and I3: 25% FC), simulating three probable scenarios of soil water content in the Mediterranean climate (adequate water supply, medium, and severe drought stress), and compared to an unfertilized treatment. The experiment was conducted in a spilt-plot design under a drip fertigation system. The results showed significant changes in chickpea phenotypic and physiological traits in response to different P and water supply regimes. Compared with the unfertilized treatment, the stomata density and conductance, chlorophyll content, photosynthesis efficiency, biomass accumulation, and plant nutrient uptake were significantly improved under P drip fertigation. The obtained results suggested that the P fertilizer form and irrigation regime providing chickpea plants with enough P and water, at the early growth stage, increased the stomatal density and conductance, which significantly improved the photosynthetic performance index (PI
) and P use efficiency (PUE), and consequently biomass accumulation and nutrient uptake. The significant correlations established between leaf stomatal density, PI
, and PUE supported the above hypothesis. We concluded that the Poly-P fertilizers applied in well-watered conditions (I1) performed the best in terms of chickpea growth improvement, nutrient uptake and use efficiency. However, their effectiveness was greatly reduced under water stress conditions, unlike the Ortho-P form which kept stable positive effects on the studied parameters.
Cadmium (Cd) is one of the most toxic elements in soil, affecting morphological, physiological, and biochemical processes in plants. Mineral plant nutrition was tested as an effective approach to ...mitigate Cd stress in several crop species. In this regard, the present study aimed to elucidate how different phosphorus (P) fertilization regimes can improve some bio-physiological processes in tomato plants exposed to Cd stress. In a hydroponic experiment, the impact of two phosphorus fertilizer forms (Polyphosphate (poly-P): condensed P-form with 100% polymerization rate and orthophosphate (ortho-P): from orthophosphoric acid) on the photosynthetic activity, plant growth, and nutrient uptake was assessed under three levels of Cd stress (0, 12, and 25 µM of CdCl2). The obtained results confirmed the negative effects of Cd stress on the chlorophyll content and the efficiency of the photosynthesis machinery. The application of poly-P fertilizer significantly improved the chlorophyll stability index (82%) under medium Cd stress (Cd12), as compared to the ortho-P form (55%). The analysis of the chlorophyll α fluorescence transient curve revealed that the amplitude of Cd effect on the different steps of electron transfer between PSII and PSI was significantly reduced under the poly-P fertilization regime compared to ortho-P, especially under Cd12. The evaluation of the RE0/RC parameter showed that the electron flux reducing end electron acceptors at the PSI acceptor side per reaction center was significantly improved in the poly-P treatment by 42% under Cd12 compared to the ortho-P treatment. Moreover, the use of poly-P fertilizer enhanced iron uptake and its stoichiometric homeostasis in the shoot tissue which maintained an adequate absorption of iron under Cd stress conditions. Findings from this study revealed for the first time that inorganic polyphosphate fertilizers can reduce Cd toxicity in tomato plants by enhancing photosynthesis activity, nutrient uptake, plant growth, and biomass accumulation despite the high level of cadmium accumulation in shoot tissues.
•Phosphorus plant nutrition was tested as an effective approach to mitigate Cd stress in tomato plants.•Tomato plants exhibited different responses to cadmium stress under contrasting P fertilizer forms.•Polyphosphate significantly improved the photosynthetic activity and plant growth under Cd stress.•Poly-P enhanced iron uptake and its stoichiometric homeostasis in the shoot which reduce necrosis symptoms under Cd stress.
Cadmium (Cd) is considered one of the heavy metals disturbing plant biophysiological functions. The potential role of phosphorus (P) nutrition in the attenuation of Cd effects on photosynthetic ...efficiency, plant growth, and cadmium uptake has been investigated in hydroponically grown tomato. Two P nutrition regimes (P15: 15 mg l
-1
; P30: 30 mg l
-1
) were assessed in the presence or absence of Cd (Cd0: 0 μM; Cd25: 25 μM of CdCl
2
). The results showed a positive effect of P30 concentration on leaf chlorophyll content and chlorophyll a fluorescence compared to P15 treatment under Cd stress (Cd25). The disturbance of electron transfer caused by Cd at K and I-steps of OJIP transient was attenuated with sufficient P supply. P30 enhanced the performance index of photosystem II and the efficiency of electron transfer to electron acceptor at PSI acceptor side. Besides, increased P concentration improved root growth parameters and biomass accumulation in the presence of Cd. It was found that root tissues accumulated more Cd than shoots and Cd translocation was reduced with increasing P concentration. Our results reveal that Cd-P interaction induced a cascade of physiological and chemical changes in plants. An optimal P nutrition can attenuate Cd stress on plant by the promotion of nitrogen and potassium uptake, which in return improved photosynthesis efficiency, enhanced biomass accumulation and distribution, and minimized Cd accumulation and translocation in plant tissues.
The Mediterranean agricultural sector faces many challenges related to water and mineral resource use for crop production and food security for an exponentially growing population. Phosphorus drip ...fertigation has recently emerged as an efficient and sustainable technique to improve water and nutrient use efficiency under such challenging pedoclimatic conditions. The classical methods for administering standard P fertilizers to crops (broadcasting and banding) have shown their limitations in terms of P acquisition and use efficiency. More than 60 % of applied P through dry P fertilizers is rapidly transformed into recalcitrant P forms and subsequently lost by soil erosion increasing the effects of P eutrophication issues on the ecosystem's sustainability. The emergence of new advanced irrigation technologies like high-frequent drip irrigation must be accompanied by the development of new P formulations with high water solubility and greater P use efficiency. This review illustrates the state of the art for P fertilizers used in Mediterranean agriculture in the last decades. An overall description is provided for the P fertilizer formulas, their physicochemical properties, as well as their suitability for drip fertigation systems and the consequent effects of their application on photosynthesis, plant growth, and crop productivity. The key factors influencing P fertilizer transformations and use efficiency under drip fertigation systems are extensively discussed in this review with a focus on the differences between orthophosphate and polyphosphate formulations.
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Maturation and conversion of somatic embryos are two crucial steps that hamper the development of efficient somatic embryogenesis systems in olive. Herein, a simple and efficient protocol for the ...maturation and conversion of olive somatic embryos is reported. Globular somatic embryos derived from seeds of cv. Dahbia were cultured on either half-strength olive (OM) or olive cyclic embryogenesis (ECO) media, with and without plant growth regulators (PGRs). The embryos reached the cotyledonary stage in 9 weeks, but those cultured on ECO medium containing 0.1 mg·L−1 6-(dimethylallylamino)purine (2iP), 0.1 mg·L−1 6-benzyladenine (BA) and 0.05 mg·L−1 indole-3-butyric acid (IBA) exhibited the largest sizes, with an average of 4.7 mm. Somatic embryo conversion into plantlets was evaluated using different culture media (half-strength OM or one-third strength Murashige and Skoog (MS)), light conditions (light or dark) and desiccation pretreatments. The highest rate of somatic embryo conversion (45%) was observed under a 16 h photoperiod on half strength OM medium containing 0.1 mg·L−1 gibberellic acid (GA3) and 0.1 mg·L−1 1-naphthalene acetic acid (NAA). The embryos that failed to germinate showed either necrosis, cotyledon greening with no further conversion, adventitious bud formation or secondary embryogenesis. The findings of this study will be beneficial for biotechnological applications in olive.
Mineral nutrient deficiencies induce a cascade of physiological, morphological, and biochemical changes in plants which reduce vegetative growth. In this work, the impact of P and K concentration ...levels on tomato plant development grown in hydroponic culture was investigated. Root morphology, chlorophyll
a
fluorescence, phosphorus (P) and potassium (K) content, and shoot and root biomass were analyzed. Root morphology showed significant differences among the plants grown in hydroponic culture with different concentrations of P and K. Plant root/shoot dry biomass ratio decreased by 22 and 35% for P
15
K
0
and P
30
K
0,
respectively, compared to the control (P
30
K
232
). The deficiency of P and K (individually or both) reduced significantly the root mass density parameter. For example, root mass density decreased by 38% at P
15
K
0
treatment compared to control. Correlation analysis showed that the P and K content ratio in shoot and root was significantly and positively correlated with root volume. Deficiencies in K and P decreased the relative size of the PSI final electron acceptor pool and the electron flow on the acceptor side of PSI. Tomato growth response depend on the availability of P and K, however, interactions between these two nutrients could influence their uptake and utilization.
Salt stress is considered one of the major constraints limiting plant growth. Here, tomato plants were grown in hydroponic culture with two salt sodium chloride concentrations (S1 = 2.8 dS m
−1
and ...S2 = 4.8 dS m
−1
). Under salt treatment, a significant decrease in chlorophyll content index and shoot and root dry weight were observed. We found that copper (Cu) was accumulated significantly in the shoot and sodium (Na) was significantly accumulated in the root. Furthermore, a significant nutrient imbalance indicated by a decrease in phosphorus (P), and potassium (K) uptake was measured. These decreases were accompanied by an increase in Na and Cu contents. A decrease in chlorophyll fluorescence yield was also observed indicating an inhibition at photosystem I acceptor sites. It seems that the downregulation of the electron transport between photosystem II and photosystem II under salt stress could be due to an imbalance in nutrient uptake.
•Salt stress induced modifications in wheat roots at anatomical and morphological levels.•Soluble P-fertilizers increased root performance and efficiency under salinity.•Polyphosphate showed a ...positive response at lower phosphorus doses.•Orthophosphate revealed significant results within the increase in P-concentration.
Understanding the role of nutrients in the alleviation of salt stress effects and the unrevealed significance of root system architecture for plant adaptation is one of the major research areas in the current context of agriculture. Root anatomy is also a valuable parameter to be considered in understanding how the root system counters soil salinity's effect on plant growth. Although Root Phosphorus Acquisition Efficiency (RPAE) under salt stress differs depending on plant species and the severity of salinity in the rhizosphere, optimising phosphorus (P) nutrition seems to bring positive results. This study was planned to investigate the combined effect of salinity and P-availability on root morphology and anatomy as well as nutrient uptake of wheat plants. A pot experiment was performed in open-field conditions using a Moroccan variety of durum wheat. Special emphasis was placed on how orthophosphate and polyphosphate fertilizer forms and phosphorus doses alter the morphology and anatomy of the roots under salt stress. Two soluble fertilizers were used: an orthophosphate (Ortho-A) and a polyphosphate (Poly-B) were applied at four P levels (0, 30, 45 and 60 ppm of P). Our findings showed that salt stress induced, at both anatomical and morphological levels, a series of modifications in the roots of wheat plants. Compared to salt-stressed and unfertilized plants, soluble P-fertilizers significantly increased soil available P, root P- content, RPAE, root length (RL), root surface area (RSA), root volume (RV), root mass density (RMD), root tissue water content (TWC), number of root tips, vascular cylinder diameter and SD/CT ratio. Furthermore, Poly-B showed a positive response in both morphological and anatomical parameters at lower doses while Ortho-A revealed significant results within the increase in P-concentration. The increased root parameters observed under P-treatments could determine the root performance and efficiency to acquire water and P and their transport to the aboveground organs of wheat plants under salinity.
Iron (Fe) deficiency is one of the most common problems of soybean. It causes upper leaves yellowing, interveinal chlorosis, stunted growth and yield loss. Manganese (Mn) deficiency affects the ...reactions in the oxygen evolving complex (OEC) of photosystem II and increase the accumulation of reactive oxygen species (ROS). The aim of this research is to study the effect of Fe and Mn deficiencies applied separately and simultaneously on physiological, biochemical, nutritional and growth (morphological) parameters of soybean cultivars (Glycine max L.). The experiment was conducted in nutrient hydroponic solution lacking Fe or Mn or both Fe and Mn. Chlorophyll content index (CCI) and chlorophyll a fluorescence were measured through time to detect nutritional disorders at an early growth stage before the apparition of visual symptoms. The results showed that Fe and Mn deficiencies had a significant negative effect on the photosynthetic efficiency, CCI, stomatal conductance, protein content and shoot/root nutrient uptakes. Iron and manganese stress conditions were found to enhance the accumulation of secondary metabolites and increase the antioxidant activity such as total polyphenol content (TPC), malondialdehyde (MDA) and superoxide dismutase (SOD). These impacts were more accentuated when Fe and Mn stress were applied simultaneously than when any of the deficiencies was applied alone. More than that, Mn stress alone did not significantly affect the biomass accumulation. The obtained results showed that, in hydroponic conditions, iron and manganese rational fertilization can improve the studied parameters.
•A significant negative effect on the photosynthetic efficiency, CCI, stomatal conductance, protein content and shoot/root nutrient uptakes.•Enhancement of the accumulation of secondary metabolites and increase the antioxidant activity such as TPC, MDA and SOD.•These impacts were more accentuated when Fe and Mn stress were applied simultaneously than when any of the deficiencies was applied alone. More than that, Mn stress alone did not significantly affect the biomass accumulation.•In hydroponic conditions, iron and manganese rational fertilization can improve the studied parameters.
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