The number of vascular plant species recorded in the present study is 161, related to 128 genera and 43 family. Asteraceae (22 species), Poaceae (21 species), Chenopodiaceae (20 species) comprise 39.1% of the total number of the recorded species. This finding agreed with Boulos, (2009), who mentioned that the highest represented families in the Egyptian flora are Asteraceae, followed by Poaceae then Chenopodiaceae, which together form about 34% of the Egyptian flora. In additions Zygophyllaceae (11 species), Caryophyllaceae (9 species), Fabaceae (9 species) and Cruciferae (8 species) together comprise 23% of the total number of species recorded in the present study. The previous seven families are considered leading taxa and constitute the main bulk of the flora of Wadi Degla Protected area. Hassan (2002) reported 75 species from area studys during (1999–2001) belonging to 28 families. According to Hussein et al., (2021), the overall floristic analysis of the Wadi Degla showed that the majority (48.2%) of the recorded flora belonged to five plant families: Asteraceae, Chenopodiaceae, Fabaceae, Zygophyllaceae, and Poaceae. El-Gamal (2008), recorded 75 species belonging to 31 families from Wadi Degla. The floristic comparison of Wadi Degla revealed an increase from 17 species (Tadros, 1936) to 88 species (El-Adawy, 2011). On the national scale, the flora of Egypt as indicated by Boulos (2009) comprises 2145 species, related to 755 genera and 129 families. This means that the flora of the Wadi Degla contributes 7.5% of the total species, 17% of the total genera and 33.3% of the total families.
Therophytes (68 species) are the most frequent life form, followed by chamaephytes (44 species). This had been confirmed by Hassan, (2002); Salama et al., (2013); Abd El-Ghani et al., (2014); Abd El-Aal et al., (2015) and Mashaly et al., (2016). The dominance of therophytes over the other life forms seems to be a response to the hot-dry climate, topographic variation and biotic influence (Heneidy and Bidak, 2001). The short life cycles of field weeds, the adverse climatic conditions, moisture deficiency and substrate instability probably led to the frequent occurrence of therophytes during the favorable season (Ayyad, 1983).
In angiosperms, sex form is considered a quantitative character which can be measured on a continuous scale between strictly male and strictly female extremes (Ahmed, 2009). In the present study, the dioecious species (4.4%) were as low as the monoecious (3.1%), but both are much rare than hermaphrodites (90.7%). Ahmed (2009) found that the percentage of dioecious angiosperm species had been reported to be low. Queenborough et al., (2009) reported that the low number of dieocious speciesmay due to that these species suffer a reproductive handicap because populations of dieocious species contain fewer seed-producing individuals. The preponderance of the hermaphroditic species (i.e. bisexual species) is a common character in the world floras e.g. 92% of the British flora are hermaphrodites (Bedair et al., 2020).
The ecological and evolution importance of bisexuality was emphasized by Bedair et al., (2020) who suggested that the coevolution of hermaphroditic flowers in addition to animal pollination might be an important improvement by early angiosperms since pollen-producing and pollen-receiving organs present in the same flower allowed for efficient simultaneous deposition and removal of pollen. Ahmed (2009) have proposed that bisexual flowers sometimes represent the optimal use of energetic resources available for reproduction, since the fixed costs associated with male and female functions would be shared.
Croteau (2010) reported that passive dispersal aids plants in the dispersion and reproduction and use dispersal units called disseminules. Many disseminules were adapted for movement by some specific dispersal agents found in the environment, such as wind, water and animal has the ability of active dispersal or species may have a motile larval stage, which include seeds, spores, and fruits. In the present study, the predominance of the sarcochores (soft and fleshy diaspores) indicated that the principal mode of dissemination was the sarcochory (zoochory). The wide distribution of ballochoric species (diaspore forcibly ejected from parent plant) may be due to the explosive nature of their fruits, which is often related to rapid desiccation and hence efficient local seed dispersal (Bedair et al., 2020). The commonness of pogonochoric (diaspore has long hairs), microsclerochoric (diaspores of very light weight) and pterochoric species (diaspore with scarious wing like appendages) and rarity of barochoric (very heavy diaspores), cyclochoric (voluminous diaspores) and desmochoric species (diaspores adhere to rough surfaces) reflect the suitability for wind dispersal in Egypt. In the present study is Ipomoea cairica that grows along banks of water bodies only auxochoric species with no disarticulating from parent plant before diaspore is deposited at a site of further development.
In general, the period from March to May (i.e., spring season) was characterized by the highest number of flowered trees and shrubs, while the period from August to January had the lowest number. In Egypt, the highest humid period of the year extended from November to April which was associated with low temperatures and evaporation; therefore, much favorable soil moisture. During this period, the plants start their growth activity reaching to the flowering and fruiting stages in March, April and May (Bedair et al., 2020). Neverthless, phanerophytes (e.g. Calotropis procera, Ficus Benjamina and Eucalyptus camaldulensis) flower from May to August. This agrees with the study of El-Khalafy (2018) who reported that most species flowered from March to May, except phanerophytes from May to August.
There are many ways in which a species can be rare; a theoretical framework of an eight celled table is proposed by (Ahmed, 2009) for the different types of rarity depending on range, habitat specificity and local abundance. In the present study, 67 plants (41.6% of the total wild species) belonged to SNN cell (small geographic, narrow habitat and non-abundant gradient), followed by LNA (large geographic, narrow habitat and abundant gradient 37 plants = 22.9%), and LWA (large geographic, wide habitat 29 plants = 18.1%) this is probably the most ignored category of inconspicuous and unspectacular plants, with large ranges, several habitats, but of consistently low populations. Taxa that belonged to SNA (small geographic, narrow habitat and abundant gradient) and SNN were the classic rarities in the sense of restricted endemics, often endangered or threatened. Both internal and external factors cause plants to become rare. Internal factors refer to the plant biological characteristics, including failures in heritability, reproduction, viability and adaptability. External factors include both natural and human factors. Natural factors refer to the ecological environment, including climate, topography, soil, and other biological factors (Chen, 2014). Taxa which have large ranges, but are associated with particular habitats were generally quite predictable in their occurrence (LNA and LNN), these taxa tend to be precarious as a result of habitat destruction (Ahmed, 2009); this may be due to human disturbances, roads and land use types.
The current flora mainly regarded as a mixture of the chorotypes belonging to Saharo-Sindian (81 species) followed by the Mediterranean (51 species) region. The effect of these phytogeographical zones was highly reflected in the flora of the study area. The Preponderance of Saharo-Sindian chorotype could be attributed to the location of Egypt in the center of Saharo-Sindian region (Barakat et al., 2014). Other floristic elements such as Euro-Siberian, Sudano-Zambezian, Cosmopolitans, Palaeotropical, Neotropical, Australian and Pantropical were in a varying miniature representation reflecting their differential capability to penetrate the region (Shaltout et al., 2015).
At a national scales, the Mediterranean (105 plants) and Sinai region (98 plants) have the highest number of wild plants in the study area. The Mediterranean vegetation was dominated by evergreen sclerophyllous shrubs that form maquis (over 2 m in height), garrigue and jaral (0.6-2m), phrygana or batha (< 0.6m) plant communities (Bedair et al., 2020). Sinai Peninsula that has rock and soil types that make existence of plants possible. In addition to the landscape that is characterized by a variety of landforms (plains, wadis, springs, salt marshes and sand dunes) (Ahmed, 2009). There was in fact a great deal of water draining down the wadis, sometimes as violent and destructive flash floods, but under normal circumstances, most of the water was underground, occasionally surfacing to produce short sections of freely flowing permanent water, thus making the area rich in plants. Desert region comes in the third order (90 plants), were plants show a number of morphphysiological features that allow them to adapt with the high aridity and low nutrient availability such as deep root systems, tolerance to high radiation levels and capacity for clonal spread, presence of thorns and spines and small leaves (Bedair et al., 2020).
One hundred and fifty species in Wadi Degla (93.2% of the total species) have at least one aspect of the potential or actual goods, of which 111 taxa that had medicinal uses. For example, leaf and root decoction of Chenopodium ambrosioides is used for diuretic bladder. Edible of leaves and fruits of Capparis spinosa are used for coughs, Urtica urens are used as an expectorant, purgative, diuretic, haemostatic, vermifuge and for treatment of eczema, rheumatism, hemorrhoids, hyperthyroidism and cancer (Kavalali et al., 2003; Hattab et al., 2020 and Elshanawany, 2017), Leaves of Hyoscyamus muticus are used for fever treatment, leaf decoction of Pluchea dioscoridis are used for infantine ailments and rheumatic pains (Ayyad, 1998; Hassan and Abdelmohsen, 2018). Rubbing young flowering branches of Achillea santolina reduces toothache and rheumatic pains, while the entire plant of Fumaria parviflora was recommended to keep vitality of children (Bolous, 1983 and Omar et al., 2018). Leaf dedoction of Anchusa hispida is diuretic and is used in the treatment of rheum atism. Leaves and flowers of Peganum harmala are used for rheumatism and stomach problems, but seeds are used as an anthelmintic and as anarcotic. Capparis spinosa is used in rheumatism, enlarged spleen and tubercular glands (Batanouny, 1999; Bidak et al., 2020 and Shams et al., 2017). Phragmites australis is a folk remedy for abscesses, arthritis, bronchitis, cancer, cholera, cough, diabetes, dropsy, dysuria, fever, flux, gout, hematuria, hemorrhage, hiccup, jaundice, leukemia, lung, nausea, rheumatism, sores, stomach, thirst and typhoid (Eid, 2009 and Eid, and Shaltout, 2020).
Eighty nine taxa (55.3% of the total species) can be grazed and browsed by the domestic and wild animals (e.g. Melilotus indicus, Trigonella stellata, Fagonia arabica, Malva parviflora, Deverra tortuosa and Sarcocornia fruticosa). There are some examples of selective use of different plant organs at different seasons. Small branches of Tamarix nilotica were apparently good for camels and goats, while sheep prefer its flowers only (Shaltout et al., 2010). Twenty nine taxa are subjected to cutting for fuel (8.0%) such as Lycium.shawii, Sarcocornia fruticosa, Nitraria retusa and Tamarix nilotica (Bedair et al., 2020). Hassan et al., (2015) and Al- Sodany et al., (2019) reported that the biomass of Calotropis procera was used in biofuel and bioenergy production.
The timber plants were limited allover Egypt, only 8 species suitable as timber (5.0%) such as Phoenix dactylifera, Tamarix aphylla and Tamarix nilotica (Shaltout and Ahmed, 2012). Fruits, flowers, vegetative and ground parts of 42 taxa (= 26.1% of the total taxa) were eaten by local inhabitants. For example, Deverra tortuosa was eaten as a salad and dates of Phoenix dactylifera were eaten (Shaltout and Ahmed, 2012). Thirty six species (22.3% of the total species) are of several traditional uses such as an ornamental value (e.g. Chrysanthemum coronarium), others are used in tanning, detergent and in making handicrafts such as Phoenix dactylifera and Luffa aegyptiaca) (Shaltout and Al-Sodany, 2002). Deverra tortuosa may be used as a natural herbicide as well as a good source for yeast control (Guetat, 2018). The wood of Phoenix dactylifera was used as a tooth brush (Shaltout and Ahmed, 2012). A recent study on Pluchea dioscoridis proved that the ethanolic leaf extract has antifungal activity (Metwally et al., 2020).
One hundred and thirty two species in Wadi Degla (82.0% of the total species) have at least one aspect of the environmental services. Sand controllers, such as sand accumulation and windbreaks, are the species which have been seen to deal effectively with drift sand such as Ammophila arenaria, Nitraria retusa and Panicum turgidum; sand controllers that make efficient wind breaks (e.g. Ricinus communis and Tamarix trees), propagate themselves when once established, either by seed or by their creeping root system. Some other species are especially useful indealing with sand in salt marsh area such as Atriplex portulacoides, and Zygophyllum album (Ahmed, 2009). Sand accumulation had the maximum contribution to the flora of Wadi degla due to the predominance of sandy soils that characterize this region (Zahran and Willis, 2009). Sand accumulators (such as Nitraria retusa, Ricinus communis and Tamarix trees) play a role in preventing soil erosion, increasing soil deposition and improving drainage of low lands (Seif El-Nasr and Bidak, 2005a). Sometimes they make efficient windbreaks that propagate themselves either by seeds or by creeping root systems such as Ricinus communis and Tamarix trees (Shaltout and Ahmed, 2012).
Threats to the world’s plants continue to increase as a result of human activities (IUCN, 2003, 2010). From the well-documented threats are solid wastes, habitat loss, poor land management, over collection, over-grazing, and climate change. Most studies suggest that the rate at which plant species are being lost, or at least reduced in numbers, is faster than the speed at which scientists; land managers, policy-makers, and others can or will respond (IUCN, 2003, 2010). One hundred and sixty one taxa in the present study are damaged during solid wastes. The human-induced threats, such as over-collection, over-grazing, solid wastes, mining, rock crusher machines, industrialization, air pollution, military activities, and urbanization (e.g., new settlements, infrastructure, water and petroleum pipelines, power station, digging new wells, and highways) give rise to alterations in habitat conditions with consequent alteration in vegetation structure and the destruction of macro- and micro-vegetation elements (Hussein et al., 2021 and Nakahama et al., 2015).
One hundred and fifty-eight species, in the study area are exposed to habitat loss due to urbanization, tourism, clearance for agriculture and construction processes is one of the major threats which impact many species in the Egyptian flora especially in the Mediterranean region. This has not only led to the complete destruction of the habitats, but also its degradation of vast areas of habitat surrounding them. Consequently, this threatens plants in these habitats e.g., Lycium shwii (Shaltout and Ahmed, 2012).
One hundred forty one species, in the study area are exposed to over-collecting and over-cutting. Most wild plants species were subjected to over-collecting and over-cutting by local inhabitants, herbalists and scientific researchers. The collection of wild native medicinal plants for commercial trade had no regulation. The most serious aspect was that it usually targets rare and localized flora leading to damage them further (Seif El-Nasr and Bidak, 2005a). Heneidy (1991) ; Heneidy and El-Darier (1995) and Ahmed et al., (2020) recorded that the human activities in Omayed area (e.g. clearing and wood cutting of natural vegetation) are more severe effective on the vegetation than the over grazing by livestock. There was an increasing demand by lo al Bedouin populations for fuel woods, targeting larger woody perennials (especially woody branches and roots). The elimination of large woody perennials (which take many years to reach mature sizes) severely reduces the structural complexity of an already highly exposed environment, rapidly accelerating soil movement and erosion, reducing water retention potential and the chances of germination of annuals and smaller plants to become established The removal of woody perennials initiates the first steps in a process of complete transformation of the natural landscape (Seif El-Nasr and Bidak, 2005a). One hundred and twenty nine species, in the study area are exposed to climate that was still somewhat theoretical until 2005, is becoming more evident and the mitigation of its effects on much localized species represents an important challenge. Due to climate change, the wild population of species could be in extreme danger in a relatively near future.
The effects of man on desert vegetation may be direct on the vegetation cover itself or indirect through their influence on the other components of the ecosystem. Human activities affecting the plant cover directly, resulting in the deterioration of desert vegetation; includes intensive collection of medicinal plants and removal of plants during the construction of roads and building of new cities (Hassan, 2002).
Some plants have defensive parts that reduce or avoid consumption by herbivores (Heneidy and Bidak, 1999). In the present study, 5 groups of physical defense were recognized in 80 taxa. The first group includes 41 plants with that have hairy leathery leaves and hairy stems; sometimes the hairs become stiff or rough and irritating (e.g. Arenaria serpyllifolia, Chenopodium ambrosioides and Diplotaxis harra). Grime and Blyth (1968) reported that epidermal hairs reduce the palatability of range species or inhibit the passage of food through the gut of animals. Diaz and Cabido (2009) reported that hairy plants may be drought-tolerance adaptations, while Perkins (2010) reported that the hairy plants could help in reflecting more sunlight, reducing detrimental heating of the plant.
The second group includes 18 plants with modified parts such as spines or spinescent branches and may be considered as grazing-resistant species (e.g. Zilla spinosa, and Cenchrus pennisetiformis) or has defensive parts in the form of densely woody pointed terminates or short spinelike branches (e.g. Lycium shawii). The defensive parts of this group (mostly shrubs or sub-shrubs) are acquired as a result of herbivores attack or are already formed in the early stages of the plant life cycle (Shaltout and Ahmed, 2012). The third group includes 17 plants that have sticky latex with unpleasant taste and odour (e.g. Hyoscyamus muticus, Haplophyllum tuberculatum and Chenopodium ambrosioides). They seem to be toxic for livestock (Shaltout and Ahmed, 2012). The fourth group includes 8 plants that are covered with scales, dots or spots such as Deverra triradiata, Deverra tortuosa and Sarcocornia fruticosa. A scale or peltate hair is a type of trichome that has a plate or shield-shaped cluster of cells attached directly to the surface or borne on a stalk of some kind and had a role in physical defense against insect herbivores (Cardoso, 2008). The fifth group includes 4 species that do not appear to have any form of defense, but they are weak plants that occur under woody plants or rocks and hence are out of reach by grazing animals.