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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. [ABSTRACT FROM AUTHOR]

The Mexican yew (Taxus globosa) is important for the production of taxol, which is used to treat several types of cancer and its seeds undergo a latent period. The objectives of this research were to study the causes of seed dormancy in this species, the types of dormancy mechanisms it undergoes and how to break such dormancy. Seeds from two regions of Mexico (northern and central region) were evaluated using 12 pre-germination treatments. The treatments consisted of warm and cold stratification, applying 500 ppm of gibberellic acid (GA4/7) at different intervals, or using alternative seed scarification methods. In addition, embryo growth was studied and a protocol for in vitro embryo culture was also tested. Seeds from the central region did not germinate, probably because of inbreeding depression in seeds that came from small fragmented populations. In contrast, seeds from the northern region of Mexico subjected to warm plus cold stratification, warm plus cold stratification plus GA4/7 application, and warm stratification plus stratification with N2 plus GA4/7 application exhibited the highest germination rates (12-14 %). In vitro embryo culture indicated that only 30% of the embryos germinated. Thus, dormancy in the Mexican Yew seems to be caused by several factors, including both morphological and physiological factors. [ABSTRACT FROM AUTHOR]

Abscisic acid (ABA) inhibits seed germination and the regulation of ABA biosynthesis has a role in maintenance of seed dormancy. The key rate-limiting step in ABA biosynthesis is catalyzed by 9-cis-epoxycarotenoid dioxygenase (NCED). Two hydroxamic acid inhibitors of carotenoid cleavage dioxygenase (CCD), D4 and D7, previously found to inhibit CCD and NCED in vitro, are shown to have the novel property of decreasing mean germination time of tomato (SolanumlycopersicumL.) seeds constitutively overexpressing LeNCED1. Post-germination, D4 exhibited no negative effects on tomato seedling growth in terms of height, dry weight, and fresh weight. Tobacco (Nicotiana tabacum L.) seeds containing a tetracycline-inducible LeNCED1 transgene were used to show that germination could be negatively and positively controlled through the chemical induction of gene expression and the chemical inhibition of the NCED protein: application of tetracycline increased mean germination time and delayed hypocotyl emergence in a similar manner to that observed when exogenous ABA was applied and this was reversed by D4 when NCED expression was induced at intermediate levels. D4 also improved germination in lettuce (Lactuca sativa L.) seeds under thermoinhibitory temperatures and in tomato seeds imbibed in high osmolarity solutions of polyethylene glycol. D4 reduced ABA and dihydrophaseic acid accumulation in tomato seeds overexpressing LeNCED1 and reduced ABA accumulation in wild type tomato seeds imbibed on polyethylene glycol. The evidence supports amode of action of D4 through NCED inhibition, and thismolecule provides a lead compound for the design of NCED inhibitors with greater specificity and potency. [ABSTRACT FROM AUTHOR]

In vitro and in vivo A. ligtu hybrid seed germination tests were conducted at different treatments: soaking in gibberellic acid (GA3) or salicylic acid (SA) (0, 100, 200 and 400 mg.l-1) and Potassium nitrate (KNO3) (0.1, 0.2, 0.4 and 0.8%) with and without stratification in 5±1 °C. Stratification had a significant effect on seed germination (p < 0.05). Maximum germination (86.67%, 96.50% after 16.44, 15.05 days under in vivo and in vitro conditions, respectively) was found in 100 mg.l-1 GA3 + 21 days of stratification and was followed by 0.8% KNO3 and 100 mg.l-1 SA along with 21 days of stratification. Mean germination time (MGT) decreased with duration of stratification and GA3, SA and KNO3 application, respectively. The present results indicated that, GA3, SA and KNO3 stimulated various growth aspects of Alstroemeria seedlings growth in both under in vitro and in vivo, but seeds treated in 100 mg.l-1 GA3 soulation was more effective. Seeds treated with SA and KNO3 without stratification and control had no germination. A.ligtu hybrid species probably exhibits a combination of physiological dormancy. Stratification at 5±1 °C for 21 days or GA3 + 21 days of stratification overcame seed dormancy and increased the germination percentage of A.ligtu hybrid seeds. Seedlings growth in vivo conditions was higher as compared with in vitro conditions. [ABSTRACT FROM AUTHOR]

Bromelia serra Griseb. (Bromeliaceae) is a terrestrial herb that grows in the understory of Chaco and Cerrado woodlands. In this study, the effects of temperature, light environment and scarification on seed germination were analyzed. Two temperature regimes (15/20 °C and 20/30 °C), three light environments (Light, Filter and Darkness; 100% light and 0.65 R:FR, 100% light and 0.09 R:FR, and without light, respectively) and two scarification treatments (Scarification for 1 min. with H2SO4 at 30% and Control without scarification). Temperature was a key factor because germination was only recorded (a small fraction of seeds and very slowly) at the 20/30 °C treatment. Seeds were indifferent to light intensity, germinating at full light, as well as at darkness. Light quality affected seed germination, with higher germination percentage at high R:FR. No effect of scarification on seed germination was recorded. The results of this work provide basic information about seed germination that could be useful for the management of this species. [ABSTRACT FROM AUTHOR]

The coastline of South Africa is characterized by extensive dune fields which are threatened by development, and thus the demand of stabilization of drift sand will increase. The non-invasive alien grass species Ammophila arenaria is at present the dominant sand stabilizer. Due to its foreign origin and invasiveness in North America its use was criticized and indigenous sand-binding species would be preferred. The germination requirements of the native Arctotheca populifolia, Ipomoea pes-caprae, Myrica cordifolia and Scaevola plumieri were investigated. The results showed that for all four species the total germination time and germination phase could be shortened and germination success (number of germinated seeds) improved. The different scarification and stratification treatments broke the dormancy of I. pes-caprae, M. cordifolia and S.plumieri, whereas the seeds of A.populifolia were not dormant. Seeds of I. pes-caprae and M.cordifolia had induced an innate dormancy, respectively, whereas the type of dormancy in seeds of S. plumieri dormancy processes remained unknown. [ABSTRACT FROM AUTHOR]