Optimizing Cucumis sativus seedling vigor: the role of pistachio wood vinegar and date palm compost in nutrient mobilization.

BACKGROUND: The goal of this research is to enhance the quality of cucumber seedlings grown in greenhouses by experimenting with various soilless culture mediums (CMs) and the application of pistachio wood vinegar (WV). The experimental setup was designed as a factorial experiment within a randomized complete block design (RCBD), in greenhouse conditions featuring three replications to assess the effects of different culture media (CMs) and concentrations of pistachio wood vinegar (WV) on cucumber seedling growth. Cucumber seeds were planted in three CMs: coco peat-peat moss, coco peat-vermicompost, and date palm compost-vermicompost mixed in a 75:25 volume-to-volume ratio. These were then treated with pistachio WV at concentrations of 0, 0.5, and 1%, applied four times during irrigation following the emergence of the third leaf. RESULTS: The study revealed that treating seedlings with 0.5% WV in the date palm compost-vermicompost CM significantly enhanced various growth parameters. Specifically, it resulted in a 90% increase in shoot fresh mass, a 59% increase in shoot dry mass, an 11% increase in root fresh mass, a 36% increase in root dry mass, a 65% increase in shoot length, a 62% increase in leaf area, a 25% increase in stem diameter, a 41% increase in relative water content (RWC), and a 6% improvement in membrane stability index (MSI), all in comparison to untreated seedlings grown in coco peat-peat moss CM. Furthermore, chlorophyll a, b, total chlorophyll, and carotenoid levels were 2.3, 2.7, 2.6, and 2.7 times higher, respectively, in seedlings treated with 0.5% WV and grown in the date palm compost-vermicompost CM, compared to those treated with the same concentration of WV but grown in coco peat-peat moss CM. Additionally, the Fv/Fm ratio saw a 52% increase. When plant nutrition was enhanced with the date palm compost-vermicompost CM and 1% WV, auxin content rose by 130% compared to seedlings grown in coco peat-peat moss CM and treated with 0.5% WV. CONCLUSIONS: The study demonstrates that using 0.5% WV in conjunction with date palm compost-vermicompost CM significantly betters the quality of cucumber seedlings, outperforming other treatment combinations.

Rooting in the Desert: A Developmental Overview on Desert Plants.

Plants, as sessile organisms, have evolved a remarkable developmental plasticity to cope with their changing environment. When growing in hostile desert conditions, plants have to grow and thrive in heat and drought. This review discusses how desert plants have adapted their root system architecture (RSA) to cope with scarce water availability and poor nutrient availability in the desert soil. First, we describe how some species can survive by developing deep tap roots to access the groundwater while others produce shallow roots to exploit the short rain seasons and unpredictable rainfalls. Then, we discuss how desert plants have evolved unique developmental programs like having determinate meristems in the case of cacti while forming a branched and compact root system that allows efficient water uptake during wet periods. The remote germination mechanism in date palms is another example of developmental adaptation to survive in the dry and hot desert surface. Date palms have also designed non-gravitropic secondary roots, termed pneumatophores, to maximize water and nutrient uptake. Next, we highlight the distinct anatomical features developed by desert species in response to drought like narrow vessels, high tissue suberization, and air spaces within the root cortex tissue. Finally, we discuss the beneficial impact of the microbiome in promoting root growth in desert conditions and how these characteristics can be exploited to engineer resilient crops with a greater ability to deal with salinity induced by irrigation and with the increasing drought caused by global warming.

Effect of date palm (Phoenix dactylifera L.) leaves on productive performance of growing lambs.

Eighteen 4-month-old lambs, with a mean live weight (LW) of 19.47 ± 0.20 kg, were used to evaluate the nutritive value of date palm leaves (DPL) ensiled with different additives in a completely randomized design. Lambs were stratified into three groups of 6 lambs each and fed a control diet comprising 60% concentrate feed mixture (CFM) and 40% DPL silage (T1). In other treatments, the DPL silage (DPLS) of the control treatment was replaced with EM1 additive-treated DPLS (T2) or El-Mofeed additive-treated DPLS (T3). Apparent digestibility, total digestible nutrient, digestible crude protein, dry matter intake, daily weight gain (DWG), price of DWG, daily profit, and economics of feed efficiency were higher (P < 0.05) for the additives-treated DPLS relative to the control, with T2 enhancing these parameters compared with T3. With exception of ruminal pH, which was reduced, concentrations of ruminal NH3-N and total volatile fatty acids (VFA) increased 4 h post feeding. However, ruminal NH3-N and total VFA were greater (P < 0.05) for the additives-treated DPLS, with T2 producing higher values than T3. Ruminal pH and feed cost/kg LW gain were lower for T2 relative to other treatments. Blood constituents were within the normal ranges for lambs, though slightly altered by treatments. Whereas serum total protein, albumin, and globulin were affected (P < 0.05) in this rank order, T1 < T3 < T2, other serum parameters were not affected. Relative feed cost and relative daily profit were lower and higher respectively for T2 than for T3. It is concluded that additives-treated DPLS is nutritionally superior to untreated DPLS as a roughage source in total mixed rations fed to growing lambs. However, for improved performance of the lambs and economic benefits, EM1-treated DPLS is recommended.

Hyperspectral Reflectance of Light-Adapted Leaves Can Predict Both Dark- and Light-Adapted Chl Fluorescence Parameters, and the Effects of Chronic Ozone Exposure on Date Palm (Phoenix dactylifera).

High-throughput and large-scale measurements of chlorophyll a fluorescence (ChlF) are of great interest to investigate the photosynthetic performance of plants in the field. Here, we tested the capability to rapidly, precisely, and simultaneously estimate the number of pulse-amplitude-modulation ChlF parameters commonly calculated from both dark- and light-adapted leaves (an operation which usually takes tens of minutes) from the reflectance of hyperspectral data collected on light-adapted leaves of date palm seedlings chronically exposed in a FACE facility to three ozone (O3) concentrations (ambient air, AA; target 1.5 × AA O3, named as moderate O3, MO; target 2 × AA O3, named as elevated O3, EO) for 75 consecutive days. Leaf spectral measurements were paired with reference measurements of ChlF, and predictive spectral models were constructed using partial least squares regression. Most of the ChlF parameters were well predicted by spectroscopic models (average model goodness-of-fit for validation, R2: 0.53-0.82). Furthermore, comparing the full-range spectral profiles (i.e., 400-2400 nm), it was possible to distinguish with high accuracy (81% of success) plants exposed to the different O3 concentrations, especially those exposed to EO from those exposed to MO and AA. This was possible even in the absence of visible foliar injury and using a moderately O3-susceptible species like the date palm. The latter view is confirmed by the few variations of the ChlF parameters, that occurred only under EO. The results of the current study could be applied in several scientific fields, such as precision agriculture and plant phenotyping.

Silicon-mediated alleviation of combined salinity and cadmium stress in date palm (Phoenix dactylifera L.) by regulating physio-hormonal alteration.

We investigated the physio-molecular effects of separate and combined cadmium (Cd; 200 µM) and salinity (NaCl; 100 mM) stress on date palm during silicon (Si; 1.0 mM) applications. The results showed that exogenous Si led to significant improvements in plant growth, as well as physiology when compared with non-Si-treated seedling under stressed (Cd/NaCl) conditions. Interestingly, Si application led to lower metal (Cd) uptake and enhanced plant macronutrient uptake under combined stress, in turn, alleviating the combined salinity- and Cd-induced oxidative stress by lowering the lipid peroxidation rate, and peroxidase and catalase activities. Furthermore, ascorbate peroxidase level and the cytosolic Cu/Zn superoxide dismutase expression were significantly enhanced by Si application under combined stress. We further analyzed the effect of Si on modulation of stress-related hormonal crosstalk. Si markedly downregulated endogenous salicylic acid, jasmonic acid, and abscisic acid under NaCl stress and combined NaCl-Cd stress. However, during Cd toxicity alone, Si showed varying accumulation of these phytohormones. The results suggest that hindering the Cd uptake and enhancing silicon accumulation ultimately led to improvement of biomass and efficiency of the antioxidant system for alleviating combined stress. Moreover, higher transcript accumulation of PROLINE TRANSPORTER 2 and GAPDH and downregulation of ABA RECEPTOR by Si treatment under combined stress in date palm seedlings indicate the stress-ameliorative role of Si. The study provides evidence of the positive influence of Si on alleviating the combined toxicity of Cd and NaCl in date palm and can be further extended for field trials in Cd- and salinity-affected areas.

Staminodes evolution and in vitro development innovation in date palm (Phoenix dactylifera L.).

The in vitro cultivation of date palm staminodes (vestigial stamens) at different stages of female floral ontogenesis confirms the persistence at an immature state of such organs at all the floral differentiation stages. This is evidenced even in fully mature female flowers. Our study revealed the advanced developmental patterns of these rudimentary structures, which bear diverse morphogenetic potentialities. In vitro cultivation of staminodes provides new opportunities for in vitro regeneration of date palm. Such developmental processes were found to be modulated by the stage of floral differentiation, which closely reflected the level of staminode maturity. Development was also impacted by the composition and concentration in plant growth regulators (NAA, BAP and 2,4-D) of the culture media. The large morphogenetic plasticity of the staminodes disposed them to evolutionary variations of the date palm reproduction system. The practical benefits (micropropagation) and the fundamental interests (evolutionary process) of our investigation are discussed.

Overexpression of a Metallothionein 2A Gene from Date Palm Confers Abiotic Stress Tolerance to Yeast and Arabidopsis thaliana.

Although the date palm tree is an extremophile with tolerance to drought and certain levels of salinity, the damage caused by extreme salt concentrations in the soil, has created a need to explore stress-responsive traits and decode their mechanisms. Metallothioneins (MTs) are low-molecular-weight cysteine-rich proteins that are known to play a role in decreasing oxidative damage during abiotic stress conditions. Our previous study identified date palm metallothionein 2A (PdMT2A) as a salt-responsive gene, which has been functionally characterized in yeast and Arabidopsis in this study. The recombinant PdMT2A protein produced in Escherichia coli showed high reactivity against the substrate 5'-dithiobis-2-nitrobenzoic acid (DTNB), implying that the protein has the property of scavenging reactive oxygen species (ROS). Heterologous overexpression of PdMT2A in yeast (Saccharomyces cerevisiae) conferred tolerance to drought, salinity and oxidative stresses. The PdMT2A gene was also overexpressed in Arabidopsis, to assess its stress protective function in planta. Compared to the wild-type control, the transgenic plants accumulated less Na+ and maintained a high K+/Na+ ratio, which could be attributed to the regulatory role of the transgene on transporters such as HKT, as demonstrated by qPCR assay. In addition, transgenic lines exhibited higher chlorophyll content, higher superoxide dismutase (SOD) activity and improved scavenging ability for reactive oxygen species (ROS), coupled with a better survival rate during salt stress conditions. Similarly, the transgenic plants also displayed better drought and oxidative stress tolerance. Collectively, both in vitro and in planta studies revealed a role for PdMT2A in salt, drought, and oxidative stress tolerance.

Optimization of photosynthesis and stomatal conductance in the date palm Phoenix dactylifera during acclimation to heat and drought.

We studied acclimation of leaf gas exchange to differing seasonal climate and soil water availability in slow-growing date palm (Phoenix dactylifera) seedlings. We used an extended Arrhenius equation to describe instantaneous temperature responses of leaf net photosynthesis (A) and stomatal conductance (G), and derived physiological parameters suitable for characterization of acclimation (Topt , Aopt and Tequ ). Optimum temperature of A (Topt ) ranged between 20-33°C in winter and 28-45°C in summer. Growth temperature (Tgrowth ) explained c. 50% of the variation in Topt , which additionally depended on leaf water status at the time of measurement. During water stress, light-saturated rates of A at Topt (i.e. Aopt ) were reduced to 30-80% of control levels, albeit not limited by CO2 supply per se. Equilibrium temperature (Tequ ), around which A/G and substomatal [CO2 ] are constant, remained tightly coupled with Topt . Our results suggest that acclimatory shifts in Topt and Aopt reflect a balance between maximization of photosynthesis and minimization of the risk of metabolic perturbations caused by imbalances in cellular [CO2 ]. This novel perspective on acclimation of leaf gas exchange is compatible with optimization theory, and might help to elucidate other acclimation and growth strategies in species adapted to differing climates.

Emergent Protective Organogenesis in Date Palms: A Morpho-Devo-Dynamic Adaptive Strategy during Early Development.

Desert plants have developed mechanisms for adapting to hostile desert conditions, yet these mechanisms remain poorly understood. Here, we describe two unique modes used by desert date palms (Phoenix dactylifera) to protect their meristematic tissues during early organogenesis. We used x-ray micro-computed tomography combined with high-resolution tissue imaging to reveal that, after germination, development of the embryo pauses while it remains inside a dividing and growing cotyledonary petiole. Transcriptomic and hormone analyses show that this developmental arrest is associated with the low expression of development-related genes and accumulation of hormones that promote dormancy and confer resistance to stress. Furthermore, organ-specific cell-type mapping demonstrates that organogenesis occurs inside the cotyledonary petiole, with identifiable root and shoot meristems and their respective stem cells. The plant body emerges from the surrounding tissues with developed leaves and a complex root system that maximizes efficient nutrient and water uptake. We further show that, similar to its role in Arabidopsis (Arabidopsis thaliana), the SHORT-ROOT homolog from date palms functions in maintaining stem cell activity and promoting formative divisions in the root ground tissue. Our findings provide insight into developmental programs that confer adaptive advantages in desert plants that thrive in hostile habitats.

Effects of temperature on the cuticular transpiration barrier of two desert plants with water-spender and water-saver strategies.

The efficacy of the cuticular transpiration barrier and its resistance to elevated temperatures are significantly higher in a typical water-saver than in a water-spender plant growing in hot desert.

Webbing life type and behavioral response of the date palm mite, Oligonychus afrasiaticus, to webbing residues on leaves and fruits of date palm.

The present study examined the webbing life type and behavioral response of date palm mite (DPM) Oligonychus afrasiaticus (McGregor) toward its webbing residues, in presence or absence of immature individuals, on leaves and fruits of date palm. DPM exhibited a complicated web life type on both the leaves and fruits of date palm, which is characterized by the following features: complicated irregular web structure; webbing density on the leaves is medium and on the fruits extremely high; eggs are always laid on the threads of web without web cover; fecal pellets are deposited on the substrate surface (both leaf and fruit); quiescent stages are on the silken web threads; and the preferred site for feeding and walking is under the web. Behavioral observation of DPM females revealed that the midrib of leaves and the base of fruits of date palm were the preferred sites for feeding and web construction. The number and development stage of DPM affected the behavioral response of females on date palm leaves but not on the fruits. DPM spent most time feeding under the web on both the leaves and fruits of date palm.

The retrospect and prospect of the applications of biotechnology in Phoenix dactylifera L.

Date palm (Phoenix dactylifera L.) is one of the most important fruit trees that contribute a major part to the economy of Middle East and North African countries. It is quintessentially called "tree of life" owing to its resilience to adverse climatic conditions, along with manifold nutritional-cum-medicinal attributes that comes from its fruits and other plant parts. Being a tree with such immense utility, it has gained substantial attention of tree breeders for its genetic advancement via in vitro biotechnological interventions. Herein, an extensive review of biotechnological research advances in date palm has been consolidated as one of the major research achievements during the past two decades. This article compares the different biotechnological techniques used in this species such as: tissue and organ culture, bioreactor-mediated large-scale propagation, cell suspension culture, embryogenic culture, protoplast culture, conservation (for short- and long-term) of germplasms, in vitro mutagenesis, in vitro selection against biotic and abiotic stresses, secondary metabolite production in vitro, and genetic transformation. This review provides an insight on crop improvement and breeding programs for improved yield and quality fruits; besides, it would undeniably facilitate the tissue culture-based research on date palm for accelerated propagation and enhanced production of quality planting materials, along with conservation and exchange of germplasms, and genetic engineering. In addition, the unexplored research methodologies and major bottlenecks identified in this review should be contemplated on in near future.

Physiological responses of date palm (Phoenix dactylifera) seedlings to acute ozone exposure at high temperature.

Vegetation in the Arabian Peninsula is facing high and steadily rising tropospheric ozone pollution. However, little is known about the impacts of elevated ozone on date palms, one of the most important indigenous economic species. To elucidate the physiological responses of date palm to peak levels of acute ozone exposure, seedlings were fumigated with 200 ppb ozone for 8 h. Net CO2 assimilation rate, stomatal conduction, total carbon, its isotope signature and total sugar contents in leaves and roots were not significantly affected by the treatment and visible symptoms of foliar damage were not induced. Ozone exposure did not affect hydrogen peroxide and thiol contents but diminished the activities of glutathione reductase and dehydroascorbate reductase, stimulated the oxidation of ascorbate, and resulted in elevated total ascorbate contents. Total nitrogen, soluble protein and lignin contents remained unchanged upon ozone exposure, but the abundance of low molecular weight nitrogen (LMWN) compounds such as amino acids and nitrate as well as other anions were strongly diminished in leaves and roots. Other nitrogen pools did not benefit from the decline of LMWN, indicating reduced uptake and/or enhanced release of these compounds into the soil as a systemic response to aboveground ozone exposure. Several phenolic compounds, concurrent with fatty acids and stearyl alcohol, accumulated in leaves, but declined in roots, whereas total phenol contents significantly increased in the roots. Together these results indicate that local and systemic changes in both, primary and secondary metabolism contribute to the high tolerance of date palms to short-term acute ozone exposure.

Storage and Viability Assessment of Date Palm Pollen.

Pollen storage and viability are very important for pollination, breeding, biodiversity, biotechnology, conservation, and other biological and non-biological studies of the date palm. Optimizing procedures and duration of storage are important for effective and long-term date palm pollen storage and viability. Here we describe pollen storage methods, such as room temperature (25-30 °C), refrigeration (4 °C), storage at 4 °C in desiccators, deep freezer (-20 °C), and cryopreservation (-196 °C). Based on pollen viability by staining and in vitro germination methods, cryopreservation is the best method for long-term storage without any significant effect on pollen viability (75-84%); however, the percentage of pollen viability depends on the storage period.

In Vitro Conservation of Date Palm Tissue Cultures.

In vitro technology offers a potential solution for the conservation of date palm germplasm. Slow growth induced by low temperature allows storage from several months up to few years. Otherwise, cryopreservation is suitable for long-term in vitro conservation, at between -79 and -196 °C. This chapter describes a protocol for cold storage at 5 °C and cryopreservation of date palm tissue cultures. For cold storage, 70% of shoot buds remain healthy after storing for 12 months at 5 °C, and callus cultures remain fully viable after 12 months of storage. For cryopreservation of embryogenic cultures using dehydration by air, apparently, 20 min air drying is the best for cryopreservation. Among different types of sugars used as osmotic agents in pre-culture medium, 1 M sucrose is the best for the survival of cryopreserved cultures. However, exposure of embryogenic cultures to vitrification solution for 60 min at 0 °C gives the highest percentage of survival and conversion to plantlets.

Cryopreservation of Date Palm Pro-Embryonic Masses Using the D Cryo-plate Technique.

In this chapter, we describe a cryopreservation (liquid nitrogen, -196 °C) protocol developed for long-term storage of date palm pro-embryonic masses (PEMs), which uses the recently established D cryo-plate technique. Clumps of PEMs (3-5 mm in size) were dissected from PEM cultures and placed on pretreatment medium containing 171 g/L sucrose for 3 days. Clumps were placed in the wells of aluminum cryo-plates in which they were made to adhere using droplets of 3% calcium alginate. PEMs were treated for 20 min with a loading solution containing 184 g/L glycerol and 136.8 g/L sucrose. They were then dehydrated for 90-120 min in the air current of a laminar airflow cabinet and immersed directly in liquid nitrogen. For rewarming, the cryo-plates holding the PEMs were immersed for 15 min in an unloading solution containing 410.4 g/L sucrose. The PEMs were then detached from the cryo-plates, placed for 3 days in the dark on posttreatment medium containing 102.6 g/L sucrose, and transferred on recovery medium under light conditions. Using this protocol, 74.6 and 95.8% recovery were achieved with the PEMs of the two cultivars tested, Sukkari and Sultany.

In Vitro Cryopreservation of Date Palm Caulogenic Meristems.

Cryopreservation is the technology of choice not only for plant genetic resource preservation but also for virus eradication and for the efficient management of large-scale micropropagation. In this chapter, we describe three cryopreservation protocols (standard vitrification, droplet vitrification, and encapsulation vitrification) for date palm highly proliferating meristems that are initiated from vitro-cultures using plant growth regulator-free MS medium. The positive impact of sucrose preculture and cold hardening treatments on survival rates is significant. Regeneration rates obtained with standard vitrification, encapsulation-vitrification, and droplet-vitrification protocols can reach 30, 40, and 70%, respectively. All regenerated plants from non-cryopreserved or cryopreserved explants don't show morphological variation by maintaining genetic integrity without adverse effect of cryogenic treatment. Cryopreservation of date palm vitro-cultures enables commercial tissue culture laboratories to move to large-scale propagation from cryopreserved cell lines producing true-to-type plants after clonal field-testing trials. When comparing the cost of cryostorage and in-field conservation of date palm cultivars, tissue cryopreservation is the most cost-effective. Moreover, many of the risks linked to field conservation like erosion due to climatic, edaphic, and phytopathologic constraints are circumvented.

In Vitro Conservation of Date Palm Shoot-Tip Explants and Callus Cultures Under Minimal Growth Conditions.

Date palm fruit production has great economic significance for many countries. There is a fundamental necessity to conserve valuable date palm germplasm, but there are various problems with in vivo and ex situ conservation. In vitro storage has several advantages over conventional germplasm conservation methods. The in vitro technique offers a developed method of slow-growth storage, which is considered as an alternate solution for short- and medium-term storage of date palm germplasm under controlled conditions. Minimal growth conditions for germplasm conservation are generally achieved by reducing growth rate through modification of environmental growing conditions and culture, by using low temperatures, and the addition of growth retardants and osmotic agents. This chapter describes a protocol for short-term in vitro conservation of date palm shoot-tip and callus cultures under slow-growth storage conditions, using sucrose as an osmotic agent and abscisic acid (ABA) as a growth retardant at 15 °C for 12 months.

In Vitro Conservation of Date Palm Somatic Embryos Using Growth-Retardant Conditions.

In vitro conservation is carried out to maintain disease-free genetic materials, in a small area, protected against pests, insects, soil problems (alkaline, acidic, excess salinity, lack of organic matter, too dry, or too wet), climatic changes, and high-multiplication potential. A requirement of successful in vitro conservation is that the plants can be regenerated into complete plants rapidly when desired. The current work describes in vitro propagation and conservation techniques employing slow-growth conditions of date palm somatic embryo cultures. Clusters of somatic embryos resulting from an indirect micropropagation protocol are conserved in MS culture medium supplemented with an osmotic agent (sucrose at 90 g/L) combined with a growth-retardant hormone (abscisic acid) at 2 mg/L incubated at low temperature (18 °C) and low light intensity (10 µmol/m2/s). The survival and plant recovery rates are recorded after 10 months. Date palm somatic embryo clusters can be conserved for up to 10 months without subculture with high survival rates. Successfully conserved somatic embryos multiply and germinate to regenerate plants with well-developed shoots and roots, which survive acclimatization and field transfer.

Encapsulation of Date Palm Somatic Embryos: Synthetic Seeds.

Synthetic seed or encapsulated somatic embryos may be used for propagation, storage, and exchange of plant germplasm and have many diverse applications in date palm cultivation. They have advantages over conventional use of offshoot material for germplasm propagation, maintenance, exchange, and transportation. This chapter describes a protocol for date palm synthetic seed production by encapsulation of somatic embryos with sodium alginate. Among three concentrations used, 3% sodium alginate followed by dropping into 2.5% calcium chloride (CaCl2) solution shows the best concentration of gel matrix for both maintenance and recovery. In addition, storage of the encapsulated date palm somatic embryos at 5 °C improves the survival and conversion into plantlets; otherwise, 20 g/L sucrose in the culture medium enhances conversion of the recovered somatic embryos to plantlets. This protocol is promising for in vitro conservation and international exchange of date palm germplasm.