Effect of temporary drought on the photosynthetic characteristics, the photosynthetic nutrient-use efficiency (PNUE, PPUE), the water-use efficiency (WUE), acetylene reduction nodule activity (ARA) and the solute accumulation has been examined in nodulated alfalfa plants. The plants were subjected to moderate or severe cycles of drought (drought-recovery). Growth decreased markedly imder the water deficit, but no significant differences were found between either level of drought. As stress progressed, the plants developed higher root/shoot ratios than Controls. ARA declined progressively during water deficit treatments and upon rewatering no recovery was observed. PNUE and PPUE markedly decreased, whereas WUE increaseď in drought treated plants. Proline and inorganic cations (K, Ca, Mg) concentrations were always higher in drought-stressed plants, but sugar (TSS) content increased only in roots and nodules. Hence, imder cyclic drought nodulated alfalfa plants adjusted osmotically and achieved an improved WUE, which suggested an enhanced drought tolerance.
Let G be a group and H an abelian group. Let J ∗ (G, H) be the set of solutions f : G → H of the Jensen functional equation f(xy) + f(xy−1 ) = 2f(x) satisfying the condition f(xyz) − f(xzy) = f(yz) − f(zy) for all x, y,z ∈ G. Let Q ∗ (G, H) be the set of solutions f : G → H of the quadratic equation f(xy) + f(xy−1 ) = 2f(x) + 2f(y) satisfying the Kannappan condition f(xyz) = f(xzy) for all x,y, z ∈ G. In this paper we determine solutions of the Whitehead equation on groups. We show that every solution f : G → H of the Whitehead equation is of the form 4f = 2ϕ + 2ψ, where 2ϕ ∈ J ∗ (G, H) and 2ψ ∈ Q ∗ (G, H). Moreover, if H has the additional property that 2h = 0 implies h = 0 for all h ∈ H, then every solution f : G → H of the Whitehead equation is of the form 2f = ϕ+ψ, where ϕ ∈ J ∗ (G, H) and 2ψ(x) = B(x,x) for some symmetric bihomomorphism B : G × G → H.