Adaptations facilitate the invasion of Cylindropuntia rosea (DC.) Backeb. (Cactaceae) in the highlands of southwestern Saudi Arabia.

The colonization and expansion of any plant species into a novel environment depend on its structural and functional characteristics. Therefore, developing better control measures for any invasive plant species requires examining and understanding the mechanisms underlying its reproduction and adaptation to the environment it invades. Recently, a novel exotic species Cylindropuntia rosea (DC.) Backeb. has been identified in Baljurashi, Al-Baha province, in southwestern Saudi Arabia. Reports suggest that this species may become invasive with the current rate of habitat expansion in Baljurashi. Although C. rosea is an important invasive species, most of its morpho-anatomical and physiological characteristics have not been examined. Therefore, the aim of this study was to investigate the morpho-anatomical and related physiological adaptations of C. rosea in its new habitats in the southwestern highlands of Saudi Arabia. We observed that the species is well-equipped for invasion with traits to handle semi-arid conditions, including some morphological and anatomical features, CAM photosynthetic pathway, high growth rate, and highly effective defense mechanisms against herbivores and insects. These morpho-anatomical and physiological characteristics contribute to the high invasiveness of this species in Saudi Arabia.

Ecological significance of floristic composition and life forms of Riyadh region, Central Saudi Arabia.

Riyadh region is one of the hardest habitats in Saudi Arabia with a hyper-arid climate. This study was conducted to investigate floristic composition and plant life forms of Riyadh region and their ecological significance. Work aimed to determine the prevailing plant families and biological spectrum of their components that reflects the phytoclimate and adaptation to hyper-arid conditions of the region. Work involved field surveys of different locations in Riyadh region where plant specimens were collected and identified. Collected plant species were then listed according to their families and data were used to assess the contribution of different plant families to the flora of the region. Study of life forms was conducted to classify recorded floristic elements into categories that reflect environmental conditions prevailing in the region. Prevailing plant families were Asteraceae (17.4%), Poaceae (11%), Brassicaceae (9.9%), and Fabaceae (7%). These percentages reflect wide ecological ranges especially for Asteraceae and Poaceae. High presence of species belonging to Astreaceae and Poaceae can be attributed to their adaptation to harsh conditions as well as to effective wind dispersal strategies of their diaspores. While the most frequent life form classes were therophytes with 52%, and chamaephytes with 30%, phanerophytes and hemicryptophytes represented 9% and 8%, respectively. Predominance of therophytes and chamaephytes over other life forms is a response to hyper arid climate with insufficient rainfall and the nature of region of few available microhabitats that can support high percentage of perennials.

Blepharis saudensis (Acanthaceae), a new species from Saudi Arabia.

Blepharis saudensis, from small islands in the Red Sea of Jazan Provence, Saudi Arabia, is described as a new species and illustrated. This species differs from other known species in this genus by having a combination of long stems, oblong-lanceolate to linear leaves with entire margins and pubescence.

Phragmites australis (Poaceae): New addition to flora of southwestern Saudi Arabia.

Phragmites australis (Poaceae) is a cosmopolitan reed grass, so far reported only in Eastern Region of Saudi Arabia. Our recent field exploration in the South West Region of Saudi Arabia resulted in documentation of this species in Gizan City (Jazan Region). The species is reported here as a first record in Jazan Region and an addition to Jazan flora. A note on distribution, ecology, and brief description of the plant is also provided.

Coffee production in southern Saudi Arabian highlands: Current status and water conservation.

Work aimed at assessing status and introducing water conservation regimes for coffee production in southern Saudi Arabian highlands. Data on farm locations, altitudes, areas, practices, irrigation, tree density, and annual coffee production were analyzed. Field experiment using chlorophyll fluorescence and different irrigation regimes was conducted to examine effects of reducing irrigation frequency on photosynthesis. Results indicated that Coffea arabica L. is commonly grown at altitudes of 1300-1400 m. Plants grown at 4-6 Trees m-2 using 100 kg ha-1 mineral fertilizer produce an average of 3 t ha-1. High frequency 2-day-intervals irrigation regime practiced by farmers during the dry season presents ecological challenge to limited local artesian water resources. Changes in chlorophyll fluorescence under 14-day-intervals irrigation regime initiated water stress that markedly inhibited Photosystem II efficiency and quantum yield and increased non-photochemical energy dissipation. Applying a 7-day-intervals irrigation regime induced less inhibitory effects on Photosystem II. Results also indicated that shifting from 2-day-intervals irrigation regime to 7-day-intervals regime improves coffee agroecology and directs coffee production towards sustainability.

Evaluation of Cytotoxic and Genotoxic Effects of Euphorbia Triaculeata Forssk. Extract

Objective: To evaluate the cytotoxic and genotoxic activity of Euphorbia triaculeata Forssk. plant extract from Jazan region, Saudi Arabia, in an in vitro cancer model, which could be beneficial in anticancer therapy against human breast cancer cell line (MCF-7), prostate cell line (PC-3), human hepatocellular carcinoma cell line (HEPG2) and normal breast epithelial cell line (MCF-10A). The human foreskin fibroblast cell line, (Hs68), was also included in the cell panel. Doxorubicin and 5-Flurouracil, broad-spectrum anticancer drugs, were used as the positive control. Methods: Cytotoxicity of Euphorbia triaculeata plant extract was investigated by employing MTT assay and the genotoxicity was assessed by using comet assay. Results: Both toxicity tests exhibited significant toxicity results. In the comet assay, the Euphorbia triaculeata extract exhibited genotoxic effects against MCF-7 DNA and PC 3 but not on HEPG2 cell lines in a time-dependent manner by increasing the mean percentage of DNA damage. Euphorbia triaculeata extract showed significant toxicity against cancer cells. Comparison with positive control signifies that cytotoxicity exhibited by methanol extract might have moderate activity. Conclusion: The present work confirmed the cytotoxicity and genotoxicity of Euphorbia triaculeata plant. However, the observed toxicity of this plant extract needs to be confirmed by additional studies. Based on our results, further examination of the potential anticancer properties of Euphorbia triaculeata plant species and the identification of the active ingredients of these extracts is warranted.

A new species of Leptadenia (Apocynaceae) and two other new records from southwestern Saudi Arabia.

Leptadenia jazanica Y. Masrahi from the province of Jazan, southwestern Saudi Arabia is described as a new species and illustrated. The species differs from the other known nearest species of the genus, Leptadenia pyrotechnica, by decumbent to scrambling habit of stems and persistent leaves. In the same province also two new records belonging to the genera Canavalia (Fabaceae) and Craterostigma (Scrophulariaceae) were collected; they were identified as Canavalia virosa (Roxb.) Wight & Arn. and Craterostigma plantagineum Hochst.

Ecological significance of wood anatomy in two lianas from arid southwestern Saudi Arabia.

The hot and arid lowlands of southwestern Saudi Arabia are home to two common lianas, Cocculus pendulus and Leptadenia arborea. This paper attempts to relate the adaptation of these two climbing woody perennials to such a harsh environment to the anatomy and hydraulic characteristics of their wood. The stems of these lianas have wood with wide xylem vessels and high hydraulic conductivity which should enhance water flow to the upper canopy despite their severe twisting. Hydraulic conductivity is further helped by the simple perforation plates of xylem vessels. The circular thickening of xylem walls gives them strength and reduces the risk of their collapse and the ensuing embolism in the advent of high tension created by severe water deficit and high evapo-transpiration demand. Wide vessels, on the other hand, are more susceptible to embolism. This problem may be overcome by reducing the solute potential of xylem sap by hydrolysis of starch grains which were found to be abundant in the vicinity of the vessels. This should help absorb water by the deep roots from the capillary fringes of the typically shallow water table in this particular habitat. Furthermore, the abundance of ray parenchyma cells between xylem groups of both lianas provides great flexibility with minimum damage to water conduits in the stem during climbing and twisted growth. It was concluded that these wood features in both lianas are crucial for survival under the harsh conditions of arid Tihama plains of southwestern Saudi Arabia.