Respostas fisiológicas e bioquímicas ao estresse de alumínio e fósforo em genótipos de batata (Solanum tuberosum)

Abstract

Aluminum (Al) toxicity and phosphorus (P) deficiency often coexist in acid soils that severely limit crop growth and production, including potato (Solanum tuberosum). Understanding the physiological mechanisms relating to plant Al and P interactions should facilitate the development of more Al-tolerant and/or P-efficient crops. The objective of this study was to investigate if P- efficiency were related to Al-tolerance and if P- efficiency was related to acid phosphatase activity. Eight potato genotypes (SMIC148-A, Dakota Rose, S. microdontum, SMINIA793101-3, SMIB106-7, SMIF212-3, SMIG145-1 and SMIJ319-7) showing different responses and/or efficiency to P were grown in a nutrient solution (pH 4.0) with 0 and 200 mg Al L−1 and P-starvation. Based on shoot length, nutrient solution consumption, and total fresh and dry weight, the potato genotypes were classified as Al-tolerant (SMIF212-3 (more tolerant), SMIC148-A and S. microdontum), Al-intermediate (SMINIA793101-3 and SMIB106-7) and Al-sensitive (Dakota Rose, SMIJ319-7 (more sensitive) and SMIG145-1). The Al-tolerance in potato genotypes appears to be related to the increase in P concentration in the tissues. The Al tolerance in genotypes (SMIC148-A and S. microdontum) might be associated with higher tissue Al immobilization due to the higher tissue P content, mainly in the leaves. The Al sensitivity in the potato genotypes under P-starvation condition was associated with decreasing P utilization and translocation efficiencies. Furthermore, the increase of Al accumulation affected the rate of uptake and distribution of nutrients in the different plant parts (roots, stem, leaf, stolon and tuber) of potato genotypes. The Al-tolerance in the SMIC148-A, S. microdontum and SMIF212-3 genotypes may be connected with highest levels of nutrients in the roots and leaves. Among the eight previously analyzed genotypes, four genotypes with contrasting Al-tolerance and P-efficiency/or responsive (Al-tolerant: SMIC148-A [NER] and SMIF212-3 [ENR]; Al-sensitive: Dakota Rose [ER] and SMIG145-1 [NENR]) were utilized to investigate the effects of Al-P interactions. Potato genotypes were grown in a nutrient solution (pH 4.0) with 0, 25 and 125 μM P and 0 or 200 mg Al L−1. In this second experiment the P supply did not influence on Al tolerance response. In both experiments, it was not observed a straight relationship between tissues APase activities and P utilization efficiency (PUE). With the objective of checking whether Al oxidative stress differs in potato genotypes, Dakota Rose (Al-sensitive) and SMIC148-A (Al-tolerant), which present distinct degrees of Al- avoidance, were cultivated in a split root system for seven days with five treatments of varying concentrations and locations of Al. In general, the Al exposure caused a reduction in growth parameters in both Al-tolerant and Al-sensitive genotypes. Furthermore, it was observed an increase in Al concentration in both Al-treated and Al-untreated root half. In both genotypes was observed decrease in the P concentration in the Al-treated root half, however, in the Al-untreated root half was observed an increased in the P concentration, mainly in the Al-tolerant genotype. In both genotypes was observed an increase in the P concentration in stem in all Al treatments, however, only in the Al-tolerant genotype was observed an increased in the leaf P concentration. In addition, in the Al-tolerant genotype the biochemistry parameters were lower affected than Al-sensitive genotype. In Al-tolerant genotype was observed an increase in the total chlorophyll and carotenoids concentration whereas in the Al-sensitive genotype was observed a decrease with Al exposure. In Al-sensitive genotype was observed an increased in the leaf and root lipid peroxidation in plants exposed at higher Al treatments. On the other hand, in the Al-tolerant genotype was not observed increase in the plants exposed at higher Al treatments. However, this difference between potato genotypes can be not related to antioxidant enzymes activities. In both genotypes, in general, the Al exposure caused a decreased in the root APX activity, an increased in the GPX activity and a slight increased in CAT activity. On the other hand, the Al-tolerance in the SMIC148-A can be associated to lower Al translocation for leaf mainly in the plants only one root half was exposed at Al and the higher ability this genotype in the remobilization P from Al-treated to Al-untreated root half.