Premium
The phosphorus requirement of N 2 ‐fixing and urea‐fed Acacia mangium
Author(s) -
RIBET JÉRǑME,
DREVON JEANJACQUES
Publication year - 1996
Publication title -
new phytologist
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.742
H-Index - 244
eISSN - 1469-8137
pISSN - 0028-646X
DOI - 10.1111/j.1469-8137.1996.tb01858.x
Subject(s) - acacia mangium , nitrogenase , phosphorus , urea , shoot , biology , phosphorus deficiency , nitrogen fixation , acacia , zoology , nodule (geology) , botany , horticulture , nitrogen , chemistry , biochemistry , paleontology , organic chemistry
summary The fast‐growing leguminous tree Acacia mangium Willd, was grown for at least 22 wk in aerated solution culture either under N 2 ‐fixing conditions or with 2 mmol urea per plant per wk. Inorganic phosphorus was supplied at between 1 and 100 μmol P 1 per plant per wk: the latter was determined to be the optimum P supply for growth. The external P requirement for growth and the efficiency of utilization of internal P were similar for both N sources. However, shoot growth and the concentrations of N and P in leaves were decreased by P deficiency to a slightly higher extent in N 2 ‐fixing plants than in urea‐fed plants. Even though P deficiency limited nodule growth more drastically than it did shoot growth, the fraction of P allocated to both nodules and nodule nitrogenase activity (acetylene reduction) increased with P deficiency. It is concluded that this increase in nitrogenase activity reflects a higher N requirement per unit nodule mass in P‐deficient plants and that, once nodules are fully functional the efficiency of utilization of internal P in N 2 ‐fixing A. mangium is high compared with that of other N 2 ‐fixing legumes.