Absorção, eficiência de uso e partição do fósforo em plantas cítricas / Uptake, use and partitioning of phosphorous in citrus plants

AUTOR(ES)
DATA DE PUBLICAÇÃO

2010

RESUMO

The low phosphorus (P) availability is often a growth-limiting to a number of crops growing in Brazil, including citrus plants. Therefore, we expected that studies about P citrus nutrition could be useful to improve the management of these plants at low-P soils. Therefore, four experiments were carried out under greenhouse conditions. As strategy, acid phosphatase activity, P fractions in the leaves, the rate of P uptake and remobilization using 32P isotopic technique, growth parameters and P use efficiency as well as phosphite (a reduced form of P, Phi) as source of P were evaluated. For these studies, citrus rookstocks varieties (CRV, Cleopatra` mandarin, Rangpur` lime, Sunki` mandarin, Swingle` citrumelo, Carrizo` citrange and Smooth Flat Seville`) and scion/rootstocks combinations ( Pêra` sweet Orange on Cleopatra` mandarin or Rangpur` lime) were seleted and combined with P supply and/or source. There were differences on plant growth and P nutrition of citrus rootstocks. But all of them responded positively to phosphorus supply. The Rangpur` lime rootstock showed the highest phosphorus uptake and utilization efficiency. Acid phosphate activity in the leaves was negatively related with P concentration and it comproved severe P deficiency of CRV. Differences in APA in the roots might contribute to variation on phosphorus uptake efficiency among CRV. The maximum values of P fractions in the leaves of CRV corresponded to: 1,25-1,32; 0,29-0,50; 0,68-0,83 and 2,5-3,2 g kg-1, for Pi, Péster, P-acid nucleic and P-total, respectively. More homogenous P fertilizer placement in the soil favored nutrient uptake and growth responses of Pêra` on Cleopatra` and Rangpur`. Pêra`/ Rangpur` plants growth more (including root system) and were more efficient in P uptake and meeting P requirements than Pêra`/ Cleopatra`. This latter scion/rootstock combination showed higher P remobilization and dependence of stored P pools to meet plant s demand. This result is in agreement with the higher APA in the mature leaves of Pêra`/ Cleopatra` than in Pêra`/ Rangpur`. The rate and phosphorus uptake efficiency were stimulated by P deficiency, while relative remobilization was reduced after P ressuply. Regardless of P avaibility in the nutrient solution, there was elevated contribution of remobilized P (average 92%) in the new shoot growth. Although the total P foliar concentration of Carrizo` citrange and Smooth Flat Seville` was increased by phosphite, this did not translate into plant growth. Phosphite use was harmful to plant growth, nutrient utilization efficiency and net gás Exchange. So, the use of phosphite did not meet the P requirements by citrus

ASSUNTO(S)

fósforo citros porta-enxertos nutrição mineral fosfitos phosphorus citrus roodstock mineral nutrition phosphites

ACESSO AO ARTIGO

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