Evaluation of phosphorus efficiency and its genotypic variations in cucumber

Through hydroponic culture，P efficiencies of 18 cucumber genotypes from different origins were evaluated，and the physiological mechanisms of genotypic variations underlying the cucumber P efficiency were primarily studied. Results showed that cucumber shoot growth was significantly inhibited，while root growth was stimulated after two-week low P treatment，as mainly indicated by decreased leaf number，leaf surface area，shoot height and stem diameter；increased ratio of root to shoot，specific root length，total root length and root surface area； as well as finer roots with reduced root diameter. Compared with cucumber seedlings at high P treatment，P contents of cucumbers under low P conditions decreased less than half of those at high P treatment，about 62.66% to 93.96%， while P use efficiencies increased by 2 to 7 times. Most root parameters（including tap root length，total root length and root surface area）were significantly related with cucumber P uptake efficiency. Cucumber P efficiency was significantly related with P uptake efficiency，but not related with P use efficiency. Low P stress changed cucumber shoot and root morphologies，significantly decreased total P efficiency and P uptake efficiency of cucumber，but increased P use efficiency，there were significant genotypic variations. Cucumber total P efficiency was mainly determined by P uptake efficiency. Among tested cucumbers，genotype 3，10，13 and 17 belonged to type I（low P efficiency and low P responsiveness），while genotype 1，14，15 and 18 belonged to type III（high P efficiency and high P responsiveness），which can be used for cultivating P-efficient cucumber varieties.