Root morphology and physiological characteristics in Carya cathayensis seedlings with low phosphorus stress.

Phosphorus（P） deficiency is one of the limiting factors to plant growth. However，scarce information is available about the effect of P deficiency on the growth of Carya cathayensis. To study root morphology，leaf photosynthesis characteristics，leaf acid phosphatase，and root secreted acid phosphatase of Carya cathayensis seedlings，a hydroponic culture experiment with treatments of sufficient P（0.1 mmolL－1） or deficient P（0.02 mmolL－1） was conducted. Results showed that compared to sufficient P，the low P treatment significantly decreased（P＜0.05） plant dry weight，plant P concentration，plant P accumulation，root length，root surface area，root volume leaf photosynthetic rate，and stomatal conductance； however，there were no significant differences for intercellular CO2 concentration. Additionally，the low P treatment significantly increased （P＜0.05） leaf acid phosphatase （by 135%） and root secreted acid phosphatase （by 159%）. Thus，the low P treatments with decreases in leaf photosynthetic rate and stomatal conductance，but no differences for intercellular CO2 concentration，showed that leaf photosynthetic rate was not due to stomatal limitation. Also，for C. cathayensis an increase in acid phosphatase activity induced by a P deficiency could be an adaptive mechanism to low P stress.［Ch，4 fig. 1 tab. 28 ref.］