Component growth efficiencies of mycorrhizal and nonmycorrhizal plants

Two mycotrophic species (Lactuca sativa and Abutilon theophrasti) and one n onmycotrophic species (Beta vulgaris) were grown in a P-deficient soil, and the effects of mycorrhizal inoculation on three variables that determine g rowth rate were assessed for each. The phosphorus-use efficiency (PUE, dW/d P) is the ratio of d. wt increase to P content increase. Plant P is the amo unt of P (the limiting resource) controlled by the plant, which can be allo cated to various purposes. The phosphorus efficiency index (PEI, dP/Pdt) is the efficiency with which plant P is used to acquire P from the soil. Inoc ulated and control plants of a given species initially contained the same a mount of P because all plants were grown from seed. Mycorrhizal colonizatio n significantly increased the PEI of Lactuca and Abutilon (by 23 and 32% re spectively). As expected, mycorrhizal inoculation did not significantly inc rease the PEI of Beta. As a result, mycorrhizal inoculation significantly i ncreased the P content of Lactuca and Abutilon, but not Beta. Mycorrhizal c olonization decreased the PUE of lettuce, but did not significantly affect that of Abutilon or Beta. Mycorrhizal inoculation therefore slightly increa sed the growth rate of Lactuca, greatly increased the growth rate of Abutil on, and ultimately had no significant effect on the growth rate of Beta.