Seed priming enhances germination and seedling growth of barley under conditions of P and Zn deficiency

Low-input production of barley on the predominantly calcareous soils in most countries of West Asia and North Africa is affected by drought and a low availability of P and Zn. Especially during the early growth stages, P and Zn deficiencies retard seedling growth, rendering the young plantlets particularly sensitive to the frequently encountered dry spells. Seed priming (soaking in water and drying back to storage moisture until use) has been shown to improve crop establishment and, in some instances, to increase crop yields. While increased seedling vigor will improve barley establishment, possible benefits are likely to be limited when P and Zn are deficient. A promising variation of the priming concept is the seed treatment with solutions containing the limiting nutrient. A series of experiments was conducted in a phytotron in 2003 to develop a nutrient-priming approach to foster the establishment of barley under marginal growing conditions. Seeds of the traditional barley cultivar Arabi aswad were soaked for 0-48 hours in water and for 12 hours in solutions containing 5-500 mM P, Zn, and P+Zn, and dried back to 12% moisture until further use. Seeds were incubated at 10degreesC, and germination was evaluated over a 6- to 8-day period. Additionally, growth and nutrient uptake of 4-week-old seedlings, grown at 25% and 100% field capacity in a typical Xerosol from Syria were evaluated. Water priming for 12 hours with subsequent seed storage of up to 9 weeks increased germination rate from 65% to 95%, and advanced germination by up to 3 days compared to unprimed seeds. Addition of 10 mM Zn and 50 mM P to the priming solution increased the P and Zn content of the seeds without affecting germination. It furthermore significantly stimulated growth and P and Zn uptake by 4-week-old seedlings and improved the water use efficiency of drought-stressed plants by 44% above that of unprimed seeds.