Effect of water on photosynthetic parameters and osmotic solute of sprouting and its intact plants of Caragna korshinskii

Water treatments were carried out to the sprouting plants (damaged plants) and its undamaged plants of Caragana korshinskii in growing period in summer. The aim was to investigate photosynthetic parameters and osmotic solutes of sprouting plants and its undamaged plants before and after watering. Before watering, the sprouting plants had higher water potential (LWP), higher photosynthetic rate (A), higher stomatal conductance (G), higher transpiration rate (E), higher photochemical efficiency of photosystem II (PSII) (△F/Fm) and the maximum quantum efficiency of PSII photochemistry (Fv/Fm), whereas undamaged shrubs had lower corresponding indexes, and had higher nonphotochemical quenching of chlorophyll fluorescence (NPQ), higher proline (Pro) and higher malondialdehyde (MDA) content. After watering, parameters were different between sprouting and undamaged shrubs. Parameters including LWP, A, G, E, Fv/Fm, △F/Fm of undamaged shrubs were all increased, while the values of NPQ and the contents of Pro as well as MDA were decreased. The content of chlorophyll a and b within sprouting plants was higher than that of it within its undamaged plants before and after watering between treatments, but did not vary significantly with water available. It was concluded that the sprouting plants had less drought stress at growing season and had higher photosynthetic efficiency by use of solar energy in photosynthesis, which resulted in a quick growth. Undamaged shrubs had lower photosynthetic efficiency under stressful conditions, which dissipated much solar energy to space by means of heat, and as a result, the growth decreased.