Dodonaea viscosa (Sapindaceae) is widespread in the mountainous highlands of the southwestern part of Kingdom of Saudi Arabia, where it is a medicinally important species for the people in Saudi Arabia. Seeds of this species were collected from Mount Atharb in Al-Baha region, at an altitude of 2100 m. The aims of this study were to determine if the seeds of D. viscosa have physical dormancy (i.e. a water-impermeable seed coat) and, if so, what treatments would break dormancy, and what conditions promote germination after dormancy has been broken. The dormancy-breaking treatments included: soaking of seeds in concentrated sulfuric acid (H 2 SO 4 ) for 10 min, immersion in boiling water for 10 min and exposure to 50 °C for 1 min. After seeds had been pre-treated with H 2 SO 4 , to break dormancy, they were incubated at constant temperatures from 5 to 35 °C, under 12-h photoperiods or in continuous darkness, and germination recorded. Salinity tolerance was investigated by incubating acid-scarified seeds in different concentrations of mM NaCl in the light at 25 °C. Untreated seeds had low final germination 30%. Seeds that had been acid-scarified, immersed in boiling water or exposed to 50 °C all achieved 91% subsequently when incubated at 25 °C. Thus, seeds of this species in Saudi Arabia have physical dormancy, which can be broken by all three treatments designed to increase the permeability of the testa. After pre-treatment, there was a broad optimum constant temperature for germination that ranged between 5 and 25 °C but germination was inhibited by higher temperatures (30 and 35 °C). Light had little effect on this germination response. Scarified seeds were also sensitive to salinity, with the highest germination in distilled water and complete inhibition in 400 mM NaCl. Seeds that failed to germinate in saline treatments were mostly able to germinate on transfer to distilled water, suggesting osmotic inhibition.
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.
Our objective was to evaluate the usefulness of the germination vs. the X-ray test in determining the initial viability of seeds of five wild species (, ,, and) from Saudi Arabia. Usually several days were required to determine the viability of all five species via germination tests. However, X-ray test will give immediate results on filled/viable seeds. Seeds of all species, except and showed high viability in both germination (96-72% at 25/15 °C, 94-70% at 35/25 °C) and X-ray (100-80%) test. Furthermore, there was a general agreement between the germination (19%, 14% at 25/15 °C and 17% and 12% at 35/25 °C) and X-ray (8%, 4%) tests in which seed viability of and was very low due to insect damaged embryo as shown in X-ray analysis. Seeds of have physical dormancy, which was broken by scarification in concentrated sulfuric acid (10 min), and they exhibited high viability in both the germination (83% at 25/15 °C and 81% at 35/25 °C) and X-ray (96%) tests. Most of the nongerminated seeds of the five species except those of and , were alive as judged by the tetrazolium test (TZ). Thus, for the five species examined, the X-ray test was proved to be a good and rapid predictor of seed viability.
Wheat ( Triticum L.) is one of the major food crops of the world, and an important component of food security. The aim of this study was to collect and preserve seeds of wheat growing in eight regions of the Kingdom of Saudi Arabia (Al-Qassim, Asir, Al-Taif, Najran, AL-Baha, Jazan, Al-Madinah and Wadi Al-Dawasir) where wheat has been cultivated since ancient times. Sixty-one accessions/samples of wheat ( Triticum aestivum ) were collected and placed in dry storage ( ex-situ conservation) at −18 °C (i.e. permanent storage). The accessions of local wheat have the ability to grow under harsh environmental conditions such as (high temperature, drought and salinity). Most of these samples were collected directly from farms, but a few were collected from markets. The most important criteria for ex-situ conservation is that seeds need to have a low moisture content (MC) and a high percentage viability. Seed MC was measured for all 61 accessions by the oven-drying method and seed viability was tested in three ways: percentage of germination, tetrazolium chloride testing, and X-ray radiography. The seed MC of the 61 accessions was uniformly very low (0.10–0.12%), and 97 to 100% of the seeds were viable. Thus, all 61 wheat accessions collected in this study have the initial requirements to remain viable for long periods of time in ex-situ conservation in the gene seed bank.
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.
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