Nasr Hassan Gomaa

Background: The genus Ephedra (Ephedraceae) is a dioecious gymnosperm, where female individuals produce the pharmacologically active ephedrine alkaloids. Identifying the sex of specimens without reproductive cones is challenging due to their xeromorphic and morphological similarity. The challenges in sex identification complicate conservation and propagation efforts. Methods: Sequence-Related Amplified Polymorphism (SRAP) markers were applied to distinguish genders in five Ephedra species, particularly the vegetative branches, as well as powdered and fragmented specimens. The fresh material for the five studied Ephedra species and two sexes per species (totaling 10 samples; 5 females & 5 males) was collected from Sinai, Egypt. Results: The SRAP marker results revealed an exclusively male-specific band, and this is not applicable in females in the studied species. The applied SRAP markers grouped males and females in different UPGMA clusters and proved their efficiency in distinguishing between males and females in the five studied species. The Polymorphic Information Content (PIC) values are low (0.16–0.38); this suggests moderate genetic diversity between the females of the studied species, reflecting slow evolutionary rates. Conclusions: The SRAP markers are efficient for identifying Ephedra species at the species and gender levels, even in the absence of sex organs and molecular sequences. Recommendation: This study recommends the use of SRAP markers for conserving and propagating female plants for ephedrine production and suggests sequencing a 95 bp male-specific band to determine if it corresponds to a known sex-linked gene.

The genus Ephedra Tourn. ex L. (Ephedraceae) is an important source with pharmacological and environmental potential. Conversely, Ephedra spp. still exhibit taxonomic complexity, especially for the specimens lacking reproductive cones. This complexity is attributed to its xeromorphic features, notably the reduced leaves and analogous assimilating branches, which make the species identification a real challenge. The current study provides a pioneering approach to distinguish fragments of Ephedra species at the gender level. This study was based on the stem anatomy and stem epidermal features using a light microscope for five species (E. alata Decne., E. aphylla Forssk., E. ciliata Fisch. & C.A.Mey., E. foeminea Forssk. and E. Ephedra pachyclada Boiss.) represented by ten genders collected from S. Sinai, Egypt. Anomocytic and brachyparacytic stomata, tanniniferous idioblasts, annual rings, a terete and furrowed outline, the number and width of tracheids, patches of cortical fibers, unicellular trichomes, druses, solitary crystals, and the activity of interfascicular cambium were among the distinguishing features that were found. Different statistical analyses were applied to explore the diversity at interspecific and intra-generic levels. This study revealed that the stem anatomy was not only an efficient tool for identifying the investigated five Ephedra species at the species level but also presented a differential key to distinguish between genders and species. In addition, our results indicated that the epidermal features played a critical role in differentiating the studied Ephedra species at the gender level. This study confirms the efficacy of stem anatomy as an identification approach for the Ephedra species at the gender level and recommends this approach to identify the fragmented Ephedra for taxonomical, pharmaceutical, and medical applications.

The genus Ephedra Tourn. ex L. (Ephedraceae) still exhibits taxonomic complexity that has not yet been resolved. This study aimed to determine the taxonomic identity of the Ephedra species in Egypt and identify the fatty acid profile and its diversity at the gender level as a taxonomic tool for specimens lacking reproductive cones. The current study provides a pioneering approach that distinguishes Ephedra species at the gender level. A total of 120 fresh individuals were collected from 20 locations representing different habitats where Ephedra plants grow in Egypt. In addition, herbarium specimens were deposited in Egyptian herbaria. The studied morphological traits included 30 vegetative characteristics and 72 traits of the reproductive organs of both genders. The fatty acid content was measured using gas–mass chromatography (GC-Mass). The taxonomic revision revealed that the Genus Ephedra was represented in the Egyptian flora by five species, Ephedra alata in section Alatae and E. aphylla, E. ciliata, E. foemina, and E. pachyclada in section Ephedra. South Sinai hosts these five species and represents the center of diversity for this genus in Egypt. The vegetative characteristics were subjected to principal component analysis (PCA), which revealed a distinct separation of the five studied species. Similarly, the cone traits treated by hierarchical clustering revealed intra-gender variations. The taxonomic key was developed based on the morphological traits to distinguish the studied species at the gender level. In total, 51 fatty acids were identified from the studied species and grouped as 18 saturated, 16 monounsaturated, and 17 polyunsaturated fatty acids. In the absence of reproductive cones, the lipid content and fatty acid composition of the vegetative parts displayed significant interspecific and intra-gender variations. Therefore, fatty acids can be used to efficiently identify the studied species when they lack reproductive cones. This study proved the efficacy of a multidisciplinary approach to identify Ephedra species at the gender level and recommends this trend for future studies of this genus.

The soil seed bank is an essential functional component of plant communities. In arid ecosystems, the island-like distribution of shrubs influences the spatial distribution of the soil seed bank. Very little is known about seed banks in deserts of the Middle East. The present study aimed to evaluate the facilitative effects of Haloxylon persicum shrubs on the soil seed bank of annual plants in a sandy desert region in northwestern Saudi Arabia during two consecutive growing seasons (2017–2018 and 2018–2019) with contrasting rainfall. A total of 480 soil samples at 12 stands were collected from two microhabitats, under shrubs and in open areas, soon after the two growing seasons. The germinable seed bank of annual plants was estimated by controlled seedling emergence method. Shrubs significantly facilitated the accumulation of seed bank beneath their canopies after the two growing seasons. In both microhabitats, the size and species richness of soil seed bank were significantly greater after the wet growing season (2018–2019) than following the dry season (2017–2018). The facilitative effects of shrubs were greater following the moister growing season than after the dry season. The effect of shrubs on seed bank–annual vegetation similarity varied between growing seasons, being greater in shrub interspaces than beneath shrub canopies for the dry growing season, while during the wet season, the similarity of the seed bank with standing annual vegetation was greater in sub-canopy microhabitat than in bare soil.

The phenotypic space encompasses the assemblage of trait combinations yielding well‐suited integrated phenotypes. At the population level, understanding the phenotypic space structure requires the quantification of among‐ and within‐population variations in traits and the correlation pattern among them. Here, we studied the phenotypic space of the annual plant Diplotaxis acris occurring in hyperarid deserts. Given the advance of warming and aridity in vast regions occupied by drylands, D. acris can indicate the successful evolutionary trajectory that many other annual plant species may follow in expanding drylands. To this end, we conducted a greenhouse experiment with 176 D. acris individuals from five Saudi populations to quantify the genetic component of variation in architectural and life history traits. We found low among‐population divergence but high among‐individual variation in all traits. In addition, all traits showed a high degree of genetic determination in our study experimental conditions. We did not find significant effects of recruitment and fecundity on fitness. Finally, all architectural traits exhibited a strong correlation pattern among them, whereas for life history traits, only higher seed germination implied earlier flowering. Seed weight appeared to be an important trait in D. acris as individuals with heavier seeds tended to advance flowering and have a more vigorous branching pattern, which led to higher fecundity. Population divergence in D. acris might be constrained by the severity of the hyperarid environment, but populations maintain high among‐individual genetic variation in all traits. Furthermore, D. acris showed phenotypic integration for architectural traits and, to a lesser extent, for life history traits. Overall, we hypothesize that D. acris may be fine‐tuned to its demanding extreme environments. Evolutionary speaking, annual plants facing increasing warming, aridity, and environmental seasonality might modify their phenotypic spaces toward new phenotypic configurations strongly dominated by correlated architectural traits enhancing fecundity and seed‐related traits advancing flowering time.

Haloxylon persicum is a well-known plant of sandy deserts, but yet, its allelopathic and phytochemical potential has not been explored. In the present study, we evaluated the effects of different concentrations (1, 2, 4, and 8%) of the aqueous extract of H. persicum shoots on seed germination and seedling growth of wheat crop and black mustard weed. The effects of the same extract on the biochemical parameters (chlorophyll a, chlorophyll b, carbohydrates content, and proline content) of wheat seedlings were also investigated. Low and moderate concentrations (1, 2, and 4%) of H. persicum aqueous extract nonsignificantly affected seed germination, shoot length, root length, fresh weight, and dry weight of wheat seedlings, whereas these parameters were negatively affected by the application of the highest extract concentration (8%). The results revealed a significant increase in proline content in wheat seedlings under all the applied concentrations of H. persicum extract. Low and moderate concentrations (1–4%) of H. persicum extract significantly enhanced chlorophyll a, chlorophyll b, and total chlorophyll content in wheat seedlings, whereas these parameters were significantly reduced when the highest extract concentration (8%) was applied. Only the lowest concentration (1%) of H. persicum extract reduced the carbohydrates content of wheat seedlings, while other concentrations showed nonsignificant effects. Concentrations of 4 and 8% of H. persicum extract reduced the seed germination percentage of black mustard. The root length, shoot length, and fresh weight of black mustard seedlings were significantly decreased by the application of 1 and 2% extract concentrations and completely inhibited in response to treatment with 4 and 8% concentrations. The dry weight of black mustard seedlings was not affected by 1 and 2% extract concentrations but completely inhibited at 4 and 8% concentrations. The methanol extract of H. persicum contains high contents of bioactive secondary metabolites, such as phenolics, flavonoids, flavonols, anthocyanins, tannins, saponins, as well as proved to has a very strong antioxidant activity of the 2,2-diphenyl-1-picrylhydrazyl radical scavenging activity (DPPH). Based on our results, we recommend the potential application of the aqueous extracts of H. persicum to control black mustard weed in wheat crops. Furthermore, H. persicum revealed an interesting phytochemical pattern with sound antioxidant activity that assigns this plant as a promising candidate to explore its detailed metabolomics profile along with potential bioactivities.

Perennial shrub-annual plant interactions play key roles in desert regions influencing the structure and dynamics of plant communities there. In the present study, carried out in northwestern Saudi Arabia, we examined the effect of Haloxylon salicornicum shrubs on their associated understory annual species across four consecutive growing seasons, along with a record of the seasonal rainfall patterns. We measured density and species richness of all the annual species in permanent quadrats located beneath individual shrubs, as well as in the spaces between shrubs. During wet growing season H. salicornicum shrubs significantly enhanced the density and species richness of sub-canopy species, whereas in the relatively dry seasons they exerted negative effects on the associated species. In all growing seasons, the presence of shrubs was associated with enhanced soil properties, including increased organic carbon content, silt + clay, and levels of nutrients (N, P and K). Shrubs improved soil moisture content beneath their canopies in the wet growing season, while in the dry seasons they had negative effects on water availability. Differences in effects of H. salicornicum on understory plants between growing seasons seem due to the temporal changes in the impact of shrubs on water availability. Our results suggest the facilitative effects of shrubs on sub-canopy annuals in arid ecosystems may switch to negative effects with increasing drought stress. We discuss the study in light of recent refinements of the well-known “stress-gradient hypothesis”.

Annual plants in arid regions germinate at different times within a growing season, from early in the season to late, and this may affect post-germination traits. For this study, I tested the effect of germination timing on post-germination life-history traits, including progeny seed germination in the desert annual Erodium laciniatum var. pulverulentum (Cav.) Boiss. Traits of November- and February-germinated individuals were studied in a field survey carried out in northwestern Saudi Arabia, and the germination of freshly matured and after-ripened seeds from both early- and late-germinated plants was assessed. Overall, E. laciniatum showed significant phenotypic plasticity in life-history traits arising from different germination times. Density, survivorship and reproductive success of early-germinated plants were all significantly greater than for those that germinated later. Late-germinated plants flowered earlier, bolted at smaller size and allocated more biomass to reproduction than did early-germinated individuals. Delayed germination shortened both flowering period and life span. Seeds produced by late-germinated plants had greater germination percentage than did seeds from early-germinated plants.

This study explores the effects of year and location on reproductive traits and flowering phenology in Retama raetam populations growing in a hyper-arid environment. Besides year, season, and location, variations in the soil seed bank were also evaluated. Germination percentage of seeds buried in soil at two different depths for one year was determined. I hypothesized that changes in water availability between years and locations would lead to variations in reproductive traits, flowering phenology, and the seed bank of R. raetam. The study was conducted at a midstream and an upstream location during 2013 and 2014 in Wadi Rishrash in the Eastern Desert of Egypt. Flower, fruit, and seed production were significantly higher in the midstream location than the upstream location and in 2014 than in 2013. Flowering onset and duration did not differ significantly between locations. Flowering occurred earlier in 2014 than in 2013 at both locations, and the flowering period was longer in 2014 than in 2013. The size of the seed bank was greater at the midstream than at the upstream location, and in summer than in spring season. Germination of seeds decreased with burial depth, but increased with burial duration. Larger individuals produced more seeds and flowered earlier than smaller plants. The size of plant was also positively correlated with flowering duration. The location and temporal variations in all these traits may be related to environmental differences between locations and differences in annual precipitation.

Annual sowthistle (Sonchus oleraceus) has been reported to produce allelopathic effects. Two greenhouse experiments were conducted to estimate the allelopathic potential of both plant residue and root exudates of S. oleraceus on flavonoid composition and nodulation in a leguminous crop, Trifolium alexandrinum, and in two leguminous weeds, Melilotus indicus and T. resupinatum. The results of high performance liquid chromatography-mass spectrometry (HPLC-MS/MS) showed that all three legumes contained six flavonoid aglycones: apigenin, daidzein, kaempferol, luteolin, myricetin and quercetin; and seven flavonoid glycosides: daidzin, genistin, hesperidin, hyperoside, kaempferol-7-O-glucoside, naringin and rutin. In general, both plant residue and root exudates had inhibitory effects on the flavonoid composition and nodulation of the target species. However, residue of S. oleraceus caused a significant increase in both individual and total detected flavonoids in T. alexandrinum. The results suggest that the phytotoxins released from S. oleraceus may restrain the biosynthesis of flavonoids in the target species, whereas the accumulated flavonoids in T. alexandrinum are allelopathic-induced metabolites and suggest a resistance mode in this crop.