Phosphorus And Potassium Deficiency Physiological Characteristics Of Tomato

The tomato (Lycopersicon esculentum Mill zaofeng) plants are used to study their physiological and biochemical responses to phosphorus deficiency and potassium deficiency. The results are as follows;1.Compared to normal phosphorus concentration([Pi]=lmM), MDA content and O2-producing rate were increased, but H202 content was almost not affected, soluble protein content was decreased in tomato leaves under phosphorus deficiency([Pi]=0.01mM). Compared to normal potassium treatment ([K+]=6mM), MDA content,O2- producing rate and H2O2 content were increased while soluble protein was decreased in tomato leaves under potassium deficiency ([K+]=0.05mM).2.Under deficiency of phosphorus and potassium, SOD activities were enhanced. Especially under phosphorus deficiency, the increasing extent of SOD activity was greater than that of potassium deficiency. POD activities were increased with extension of treatment time while CAT activities were decreased during the same time. Under potassium deficiency, the activities of ascorbate-dependent H2O2 scavenging enzyme system were increased with extension of treatment time, but under phosphorus deficiency, the activities were not affected.3.Under saturation light intensities, net photosynthetic rates (Pn) under deficiencies of phosphorus and potassium were significantly decreased. Pns were 67.4% and 36.4% of their respective controls'. Under saturation CO2 concentrations, Pns were drastically decreased too, which were 58.1% and51.6% of their respective controls'. Studies on the chlorophyll fluorescence showed that Fo were increased while Fv and Fm were both decreased under both deficiencies. Fv/Fm, Fv/Fo, Fv'/Fm, PS II, qP, qNP, NPQ and ETR were all decreased to different extent under potassium deficiency. Under phosphorus deficiency, except the enhancement of qNP and NPQ, all other parameters were decreased and the decreasing extents of the parameters were greater than the same parameters under potassium deficiency. Thus, it indicated that apparent photoinhibition happened under both deficiencies, but the extent of the inhibition under phosphorus deficiency was severer than that under potassium deficiency. Because of the enhancement of qNP and NPQ under phosphorus deficiency, radiationless energy dissipation was enhanced to decrease the excessive energy to produce active oxygen species to ameliorate photoinhibition to some extent.4.After 25 days of treatment, the shoot/root ratio under phosphorus deficiency decreased, and increased under potassium deficiency and Correspondingly, concentrations of sucrose, reducing sugars and total soluble sugars were also differently affected by low nutrition supply. Under K deficiency, the concentrations of sucrose, reducing sugars and total soluble sugars were much higher than those in control and P-deficient plants. In contrast, the lowest concentrations of sucrose, reducing sugars and total soluble sugars were found in roots of K-deficient plants, whereas the concentrations of sucrose, reducing sugars and total soluble sugars were particular high in roots of P-deficient plants. Of the total amounts of soluble sugars per plant, the following proportions were partitioned to the roots,11.30% in K-deficient, 46.65% in P-deficient,31.19% and 33.38% in their respective control plants. The results indicated a distinct role of K andP in the translocation of photosynthates. Dry matter distribution between shoots and roots of plants were different suffering from different mineral nutrient deficiencies.