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Distribution of copper and zinc in subterranean clover in relation to deficiency diagnosis

Reuter, D.J. (1980) Distribution of copper and zinc in subterranean clover in relation to deficiency diagnosis. PhD thesis, Murdoch University.

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Glasshouse experiments were conducted to determine the effects of copper and zinc deficiencies on the growth, development, and the pattern of distribution of both elements in Seaton Park subterranean clover. Criteria for diagnosing copper and zinc deficiencies by plant analysis were developed. The effects of phosphorus supply on the distribution of copper and zinc within plant tops and on the diagnostic criteria were examined in separate experiments.

Symptoms of severe and moderate zinc deficiencies were characteristic and easily recognised, but those of severe copper deficiency and of marginal zinc deficiency were much less distinctive. Severe deficiencies of both elements delayed phasic development, depressed top growth more than root growth, depressed the yield of plant tops by reducing the number, yield and rate of appearance of individual plant parts, decreased the size and proliferation of root nodules, reduced the transport of both nutrients from the roots to the tops, increased the yield of the combined leaf blades relative to the yield of the combined stems plus petioles and decreased the proportion of copper and zinc accumulated by the plant top and located in the combined leaf blades. Copper deficiency also depressed seed yield by reducing the number of burrs and seeds formed.

The redistribution during growth of both copper and zinc from the older trifoliate leaf blades of deficient plants was markedly restricted. As a result, early deficiency symptoms of both elements were observed in young trifoliate leaves. Nett losses of zinc also did not occur from older blades of plants of high zinc status even when they began to senesce. In contrast, copper was redistributed from senescing blades of copper adequate plants, but at full senescence these blades still contained quantities and concentrations of copper, which reflected the level of copper supply.

In all experiments, the concentrations of copper and zinc in young leaf blades provided reliable indices of the copper and zinc status of plants. The critical concentrations were for copper, 3 µg/g in the youngest open trifoliate leaf blades, (YOL) and for zinc 13 µg/g Inthe same organ. These critical levels remained constant during vegetative growth and were similar at early flowering for copper. Critical concentrations for copper in new emerging blades were slightly higher and were substantially higher for zinc. In addition, concentrations in leaf blades of copper and zinc sufficient plants were always greater than those in the petioles, but in deficient plants these differences were much smaller.

Difficulties were encountered in interpreting the analysis of copper in whole plant tops. Critical concentrations decreased with increasing plant age, and "Piper-Steenbjerg" curvature developed in the relationship between yield and concentration at late stages of vegetative development. This curvature was caused primarily by unusually high copper concentrations in the older stems and petioles of severely deficient plants.

Most interactions between phosphorus and copper and between phosphorus and zinc were positive and indirect. As a consequence, the estimated critical concentrations of copper and zinc in young leaf blades were the same for plants moderately deficient or adequately supplied with phosphorus. Unreliable values of copper only occurred in leaves of severely phosphorus deficient plants grown at low copper supply: although their growth was not limited by copper, their organs had concentrations below critical values established for plants moderately deficient or adequately supplied with phosphorus.

Item Type: Thesis (PhD)
Murdoch Affiliation(s): School of Environmental and Life Sciences
Notes: Note to the author: If you would like to make your thesis openly available on Murdoch University Library's Research Repository, please contact: Thank you.
Supervisor(s): Loneragan, Jack and Robson, A.D.
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