The Research Of Physiological Mechanism About Increasing Lateral Root Of Phaseolus Coccineus L. Under P Deficiency

Phosphorus (P) is a indispensably vital element in the life of plant which play importantroles in many physiological and energy metabolic process. But plants always suffer with Pdeficiency due to its low-availability in many soils. To resist P deficient, many pieces of planthave evolved some physiological and morphological adaptions. Among these changes, anotable one is the changes of root-system morphology.In this paper, we researched and analyzed the correlations between the roots morphologychanges under P deficiency and IAA synthesis and metabolisim by solution culture method.And here are the results:1. The increasing lateral roots were triggered by indole-3-acetic acid (IAA) under Pdeficiency. Exogenous IAA significantly increased lateral roots (contained secondary andtertiary roots) formation, but it was not able to perfectly mimic the effects of P starvationsignal on phaseolus coccineus L. root architecture. The application of IAA polar transportinhibitor TIBA caused the suppression of roots growing. All these data demonstrated that IAAwas the necessary condition for the formation of lateral root, and in a certain range, it couldincrease the number of lateral roots.2. P deficiency and exogenous IAA both could up-regulate the activities of IAAO andPOD. And TIBA suppressed the activities of IAAO and POD which should be increased underP deficiency. These result confirmed that intensify of IAA metabolisim could be regulated butits own concentration. In addition, IAAO and POD activities showed significant regularity inthe process of lateral roots.3. The increasing IAA concentration were not only from IAA polar transport,but alsofrom IAA synthesis. The increasing total Zn content of whole plant under P deficiencydemonstrated that P insufficiency could enhance the Zn absorption of phaseolus coccineus L.seedlings. The proportion of Zn distribution in roots were rose by P deficiency while theconcentration of Zn in stalk down. This change of Zn distribution demonstrated that Pdeficiency transfer more Zn to root from other organ in order to supply for IAA synthesis.And concentraton of trp were significantly affected by the P level in the solution. Trp concentration of phaseolus coccineus L. seedlings growing under P deficiency significantlydecreased by P deficiency demonstrated that IAA synthesis present in root as well as in shoottip.In conclusion, under P deficiency, phaseolus coccineus L. regulated the IAAconcentration in roots by strengthening its synthesis and metabolisim, in order to achieve thepurpose of root morphology changes.