The effect of high pH and P on the development of lime-chlorosis in two seedling populations ofEucalyptus obliqua L'Hérit |
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Authors: | C A Anderson |
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Institution: | (1) Botany Department, Monash University, 3168 Clayton, Victoria, Australia |
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Abstract: | Summary Glasshouse experiments have shown that the application of an acidulating agent to a calcareous soil can increase growth and
alleviate severe chlorosis in an acidic population ofE. obliqua. In contrast, a calcareous population showed only a slight response to this treatment and maintained adequate growth and
a low frequency of chlorosis on both control and treated calcareous soils. Foliar analyses of seedlings of the acidic population
showed that alleviation of chlorosis was concomitant with a reduction in the levels of P, Ca and K, and an increase in uptake
of Fe. However, the total Fe content of foliage was poorly correlated with the occurrence of severe chlorosis. Although this
evidence suggested that the differential susceptibility ofE. obliqua to lime-chlorosis can be reduced by increasing the availability of Fe, the greater concentration of Fe in chlorotic seedlings
indicated that lime-chlorosis may also be due to an inactivation of Fe within the plant (i.e. by P).
This hypothesis was partly confirmed by a water culture experiment which showed that a combination of relatively high pH and
high external levels of P could induce severe chlorosis in seedlings of the acidic population. In contrast, it appears that
the calcareous population has a more efficient mechanism for absorbing Fe and holding it in an available form, even when external
concentrations of P are high. It is suggested that plants which have an efficient mechanism for the uptake of Fe at relatively
high pH and are less susceptible to the detrimental effects of P have been selected for on these alkaline calcareous soils. |
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Keywords: | Calcareous Eucalyptus obliqua Iron availability pH Phosphorus Soil acidulation |
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