Problem statement: Water stress due to drought and salinity is probably the most significant abiotic factor limiting plant and also crop growth and development. Salinity and drought stresses are physiologically related, because both induce osmotic stress and most of the metabolic responses of the affected plants are similar to some extent. Water deficit affects the germination of seed and the growth of seedlings negatively. Temperature is an exceedingly important factor in seed germination. It directly affects whether a plant can sprout and, if so, how long it will take to emerge from the ground. Approach: The objective of this investigation was to determine the effect of four alternating temperature regime, drought and salt stress on germination characteristics of Pennisetum divisum. Seeds were germinated at four alternating temperatures (10/20, 15/25, 20/35 and 25/40°C at 12 h light). Seeds were also germinated with the iso-osmotic concentrations of sodium chloride (NaCl) or in polyethylene glycol PEG8000 (0, -0.2, -0.4, -0.6 and -0.8 MPa) for 14 days. Concentrations were applied to determine their effects on seed germination and seedling growth under laboratory conditions. The effects of different osmotic concentrations of NaCl and PEG were compared to distilled water (control). Results: Optimum germination was attained at 15/25°C which corresponds to temperatures prevailing during spring time. The highest values of germination parameters were obtained with no osmotic potential (0 MPa) under 15/25°C. The final germination percentage and rate of germination in the Pennisetum divisum treated seeds were decreased with the increase of the osmotic potential. At treatment by PEG, the germination was severely decreased at -0.6 MPa. While, no germination occurred at-0.8 MPa by NaCl. The results of the effects of the different osmotic potential of NaCl and PEG on the Radicle Length (RL) and the Hypocotyl Length (HL) mm of the tested P. divisum seeds were retarded when compared to the control. Conclusion: Results indicated germination sensitive to both the stresses. However, seedling growth was more sensitive to NaCl than was germination. However, seedling growth was more sensitive to NaCl than was germination responses to water stress induced by PEG and NaCl. Results also indicated that seed germination of P. divisum is less sensitive to osmotic potential indicating that the seeds of the species are efficient in osmotically adjusting to soluble salts. This suggests the possibility of revegtating moderately salt affected soils.

Geophytes are plants with underground storage organs including bulbs, corms, tubers, and rhizomes, often physiologically active and able to survive during harsh environmental conditions. This study is conducted to assess the nutritive value, mineral composition, bioactive metabolites, and antioxidant activity of five wild geophytes (Cyperus capitatus, C. conglomeratus, Elymus farctus, Lasiurus scindicus, and Panicum turgidum) collected from the Nile Delta coast and inland desert. The proximate composition including dry matter, moisture content, ash content, fiber, fat, protein, sucrose, and glucose were determined. Also, total carbohydrates, total digestible nutrients (TDN), and nutritive values were calculated. Macro- and micro-minerals were also determined in the studied geophytes. Total phenolics, total flavonoids, alkaloids, saponins, and tannins were determined. Antioxidant activity was evaluated based on 2,2-diphenyl-1-picrylhydrazyl (DPPH) radicle scavenging. Based on the nutritive value, the studied geophytes are ranked as follows: E. farctus > C. conglomeratus > L. scindicus > P. turgidum > C. capitatus. The mineral analysis reveals a sufficient amount of macro- and micro-elements in the studied geophytes while the microelements levels in the studied wild plants exist as Fe > Mn > Zn > Cu. Cyperus conglomeratus attained the highest concentrations of all determined secondary metabolites. On the other hand, C. conglomeratus, C. capitatus, and P. turgidum extracts showed strong scavenging activity (EC50 < 1 mg mL−1), while extracts of E. farctus and L. scindicus exhibited moderate scavenging activity (1 ≤ EC50 ≤ 2 mg mL−1). The present data reveal that geophytes under investigation could be used as good forage plants, especially in arid habitats. In addition, C. conglomeratus could be a potentially important candidate for natural antioxidants as it attained high contents of the bioactive constituents.

Invasive species are considered as one of the major threats to ecosystems worldwide. Although invasive plants are regarded as a foe, they could be considered as natural resources for valuable bioactive compounds. The present study aimed to characterize the chemical composition of the essential oil (EO) from the invasive plant Argemone ochroleuca Sweet, collected from Saudi Arabia, as well as to evaluate its phytotoxic activity. Seventy-four compounds were characterized via GC-MS analysis of EO representing 98.75% of the overall mass. The oxygenated constituents (79.01%) were found as the main constituents, including mono- (43.27%), sesqui- (17.67%), and di-terpenes (0.53%), as well as hydrocarbons (16.81%) and carotenoids (0.73%). Additionally, 19.69% from the overall mass was characterized as non-oxygenated compounds with mono- (1.77%), sesquiterpenes (17.41%), and hydrocarbons (0.56%) as minors. From all identified constituents, trans-chrysanthenyl acetate (25.71%), γ-cadinene (11.70%), oleic acid, methyl ester (7.37%), terpinene-4-ol (4.77%), dihydromyrcenol (2.90%), α-muurolene (1.77%), and γ-himachalene (1.56%) were found as abundant. The EO of A. ochroleuca showed significant phytotoxic activity against the test plant Lactuca sativa and the noxious weed Peganum harmala. The EO attained IC50 values of 92.1, 128.6, and 131.6 µL L−1 for seedling root growth, germination, and shoot growth of L. sativa, respectively, while it had IC50 values of 134.8, 145.7, and 147.9 µL L−1, respectively, for P. harmala. Therefore, this EO could be used as a bioherbicide against weeds, while further study is recommended for the characterization of the authentic materials of the main compounds in the EO as well as for the evaluation of potency of this oil on a field scale and the determination of its biosafety.

Ephedra alata Decne is a perennial shrub and it is a very effective sand-binder. In Saudi Arabia, the species is associated with sand dunes formation, especially the mobile, non-saline and low moisture content ones. Its geographical distribution in Saudi Arabia includes the Northern, Eastern and Central regions. The aims of this study were to determine the effects of temperature, water potential and Sodium Chloride on germination of E. alata. Seeds were collected from King Khalid Centre of Wildlife Research and Development at Thumama (80 km north east of Riyadh), Saudi Arabia. Seeds were germinated at four alternating temperature regimes (8/22; 9/23; 13/27 and 18/35 °C). Seeds were also germinated under stress of aqueous Polyethylene Glycol (PEG) solutions mixed to create water potentials of 0; -0.3; -0.6; -1.2 and -1.5 MPa. Seed were also germinated in Sodium Chloride solutions of 0, 0.05, 0.1, 0.2 and 0.3 mol l(-1). Optimum germination was attained at 13/28 °C that corresponds to temperatures prevailing during spring time. Seeds germinated in Polyethylene Glycol solutions exhibited significantly lower germination than control especially when water potential fell below -0.3 MPa. Germination was also negatively affected by 0.1 mol l(-1) Sodium Chloride solution or above. Results indicated that the germination temperature responses of the nondormant seeds synchronize the event of germination with the season when environmental conditions are more favorable for subsequent growth and seedling establishment. Germination was also sensitive to both water potential and salinity.

Mangrove forests are of special interest because of their metal accumulation potenials as they occur in environments characterized by an excess of toxic ions. In this current study, we investigated the accumulation capacity of (Avicennia marina), a dominant mangrove plant inhabiting Tarut Bay in Eastern Saudi Arabia. Samples comprising mangroves, water and soil from 10 locations of Tarut Bay were analyzed for 8 heavy metals including Boron, Iron, Manganese, Zink, Lead, Nickel, Cadimum and Cupper. In water samples, B (5.5 PPM) was the highest while Cd was absent, also soil samples contained higher B (27.2 PPM), while Cd was lacking in these samples too. Overall, the concentrations of heavy metals were higher in plant shoot as compared to water and soil samples. In plant shoot Cu level was highest (107.22 PPM), while Cd was the lowest in. Our results demonstrate that grey mangrove absorb and accumulate higher quantities of heavy metals and thus play a vital role via cleansing the coastal environment from such harmful heavy metals. Our findings asserted that grey mangrove is a promising candidate for the purpose of Phytostabilization of industrially polluted coastal shores.

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In this review, we discuss the relationship between environmental crop management and adaptation to warming climates of legume plants and plant breeding, for drought tolerance. The benefits connected to the impact of the expansion of appropriate legumes-based agriculture for arid zones are analyzed. We need to two aims to develop programs of breeding and management guided to drought tolerance. The first one is enhancing productivity. The second one is to improve the drought tolerance by mechanisms of water conservation.

Problem Statement: Many soils of different areas of the world are subjected to heavy metal pollution due to human activities especially the industry. These metals are hazardous to human health and could affect ecosystems. Toxic metal pollution in water and soil is a major environmental problem and most conventional remediation approaches do not provide acceptable solution, hence the studies of reducing such effects were launched. Phytoremediation, popularly known as green clean is an ecologically recommended strategy for the removal of toxic contaminations from the environment by using plants. Approach: The present study is an attempt to assess the suitability of using two species namely: Phragmites australis and Ttamarix aphylla as vegetation filterers in an industrial area to reduce the danger of contamination of heavy metals in the environment. The studied species viz. Phragmites australis and Tamarix aphylla were collected at four different locations (A, B, C and D) around a petrochemical and detergents factory in the industrial areas of Eastern Region, Dammam city, Saudi Arabia. The concentrations of seven heavy metals (Fe, Mn, Zn, Pb, Ni, Cd and Cu) were evaluated in different organs of Phragmites australis and Tamarix aphylla. Also, Soil samples were collected from each location for the chemical and mechanical analyses. Results: The results showed that the concentrations of heavy metals in Phragmites australis and Tamarix aphllya exhibited the same trend. In shoots of the studied species, Zn accumulated less heavy metals than the under ground parts, creeping rhizome and roots. The highest bioaccumulation factor (BAF) for Cd and Zn was noted in location B. In general, Zn was the most absorbed element followed by Fe, Mn while Ni as well as Pb and Cd were accumulated in lower quantities. In chemical and physical analyses of soil samples, location C showed the highest concentration of all of the investigated elements and it is the most alkaline with more clay and organic carbon. Conclusion/Recommendation: The present results demonstrated that both species are significant as vegetation filter and for cleaning the soils from contamination with heavy metals by phytoextraction. There is a great need to use the advantages of these plants in phytoremediation of environment. In the same time continuous harvesting of their shoots could be suitable way to recycling heavy metals