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Phosphorus regulates osmotic potential and growth of African violet under in vitro-induced water deficit

Sawwan, J., Shibli, R.A., Swaidat, I., Tahat, M.
Journal of plant nutrition 2000 v.23 no.6 pp. 759-771
height, plant characteristics, Saintpaulia ionantha, phosphorus, osmotic pressure, water stress, sorbitol, mannitol, sap, shoots, roots, length, plant physiology, culture media, mortality
Interactive effects of phosphorus (P) with in vitro-induced water deficit (using sorbitol and mannitol) were studied on African violet (Saintpaulia ionantha) whole-plant microculture. Sorbitol and mannitol significantly reduced (more negative) the cell sap osmotic potential. Increased P was very effective in increasing (less negative) the osmotic potential of cell sap under the imposed water deficit treatments. On the other hand, induced water deficit significantly reduced shoot growth (shoot height and dry mass), and root number and length, whereas P mitigated these adverse effects and improved shoot and root growth. Cultures exposed to water deficit at 150 mM sorbitol and mannitol experienced some physiological disorders (about 10% shoot tip browning, 15% stem basal-end browning) and 20% chlorosis. Physiological disorders and chlorosis were totally mitigated with increased P to 1.0 or 2.0 mM. Phosphorus concentration in shoot tissues was decreased with water deficit in the medium and enhanced by elevated P in the medium. Ex vitro survival percentages increased in plantlets that experienced in vitro water deficit with sorbitol and mannitol at 50 to 100 mM and P at 1.0 to 2.0 mM. We conclude that P is a key factor to regulate cell osmotic potential and growth under in vitro induced water deficit. On the other hand, microculture level is a very effective alternative for the study of plant response and tolerance to water deficit and its interaction with nutrient availability in the root zone.