Abstract:

One-year-old potting apple saplings were used to study effects of soil drought stress and oligo-chitosan on the osmotic adjustment ability. The saplings were treated with different soil drought degrees and drying speed. The results showed that apple sapling had remarkable osmotic adjustment ability under drought stress, and the ability was influenced by the soil drought degree and drying speed. Under slowly soil drying, ψ_w, 100 of the apple leaves descended obviously. The 100 value under slowly drying was 35 times greater compared with the value under rapidly drying. With slowly drying, the osmotic adjustment increased from mild to moderate drought, while it did not any more from moderate to severe drought stress. Contents of Pro, amino acids and sugars increased under the mild and moderate drought, and the relative contribution of the three osmotica to osmotic adjustment was in such an order: sugars Pro amino acids.

Key words: one-year-old apple saplings, drought stress, oligo-chitosan, osmotic adjustment ability