| Three putative osmolytes, betaine, proline and DMSP, increased with time and/or salinity levels. The osmolality of the combined three compounds occupy 1–8% of that of the cell sap. A strong response of betaine and proline was detected in roots and flowers and DMSP in leaves, indicating osmotic adjustment is crucial in salt sensitive tissues. The highest levels of all examined compounds occurred in the flowers, and all three substances showed a basipetal gradient in flower stalks. This is the first report of DMSP in the Iridaceae .; Salinity increased endogenous Na+ levels 2–20 folds in leaves and roots and > 2 fold in ovaries and stalks but Na+ did not accumulate in rhizomes. Overall, K, Ca, P and S decreased in leaves, roots, rhizomes, petals or ovaries while the divalent ions Mg and Mn increased. The contents of Cu, Fe, and Zn were not affected by salinity stress. Leaf pretreatment with ABA, IAA and SA affected the ion balance by reducing Na + accumulation and increasing the levels of other ions. Four different ratios (K/Na, Mg/Na, Ca/Na, and P/Na) were proposed as the criteria for iris salinity resistance.; ABA and JA generally increased, while IAA and SA declined in response to salinity. Hormone contents were delicately controlled in the flower stalks during flower development. Protein expression patterns evolved differentially in leaves, roots and rhizomes with time and/or salinity levels. Comparison of proteins induced by salinity, sorbitol and hormone (ABA, JA and SA) in iris seedlings showed that leaves were not as sensitive as roots. Some proteins were expressed by all stimuli, but each stimulus induced or enhanced certain unique proteins. Osmotic adjustment and maintaining ion homeostasis contributed to the salinity resistance of iris plants. This process is regulated by proteins and/or phytohormones. |
