6. CONCLUSÕES: O presente estudo propiciou as seguintes conclusões: 6.1. Determinação da tolerância ao alumínio - As cultivares estudadas se distribuem em pelo menos 4 grupos de tolerância ao alumínio (tolerância diminui de 1 para 4). Grupo 1 – IAS 20, IAS 54, IAS 55, IAS 60, IAS 63, CNT₁, PF 70354, PF 70546, Horto, Coxilha e PAT 19; Grupo 2 – IAS 57, IAS 61, C 33, Frontana, CNT₂, Nobre, Maringá, Londrina e PAT 24; Grupo 3 – Yecora, LA 1549, IAS 58, IAS 64, Toropi, Pel 72018 e Pel 72083; Grupo 4 – Sonora 63 P, Sonora 63 C e Super X. 6.2. Determinação da tolerância ao manganês - As cultivares estudadas se distribuem em 3 grupos de tolerância ao manganês: Tolerantes – Sonora 63 C, Super X, Yecora, LA 1549, IAS 20, IAS 54, IAS 55, IAS 57, IAS 58, IAS 60, IAS 61, IAS 63, IAS 64, C33, Toropi, CNT₂, Nobre, PF 70354, PF 70546, Pel 72018, Pel 72083, Horto, Coxilha, Londrina, PAT 19 e PAT 24. Tolerância intermediária – Sonora 63 C e Maringá. Suscetíveis - CNT₁ e Frontana. 6.3. Concentração de nutrientes - a) O grau de tolerância ao alumínio das cultivares de trigo não está relacionado com as concentrações de P, Ca e Mg das partes aéreas. b) As concentrações de P, Ca e Mg das partes aéreas das cultivares se comportam diferentemente em função das concentrações de Al na solução. c) O grau de tolerância ao manganês das cultivares de trigo não está relacionado com as concentrações de P, Ca, Mg, Fe, Mn, Zn e Cu das partes aéreas e Ca, Fe e Mn das raízes. d) As concentrações de P, Ca, Mg, Fe, Mn, Zn e Cu das partes aéreas e Ca, Fe e Mn das raízes das cultivares se comportam diferentemente em função das concentrações de Mn na solução. 6.4. Absorção de cálcio - a) A absorção de cálcio se realiza através de dois mecanismos. b) Na ausência de alumínio e de manganês existem diferenças genéticas na absorção de cálcio somente na faixa de concentração correspondente a 1,6 x 10^-4M – 2,56 x 10^-3M e estas não estão relacionadas com o grau de tolerância ao alumínio e ao manganês. c) O alumínio promove na absorção do cálcio: - uma inibição competitiva (faixa de concentração correspondente a 5 x 10^-6M – 8 x 10^-5M; - uma inibição competitiva na cultivar Sonora 63 C e uma estimulação nas cultivares IAS 63 e Yecora (faixa de concentração correspondente a 1,6 x 10^-4M – 2,56 x 10^-3M). d) O manganês promove na absorção do cálcio: - uma inibição competitiva nas cultivares Sonora 63 C e CNT₁ e uma inibição, provavelmente incompetitiva, na cultirva IAS 55 (faixa de concentração correspondente a 5 x 10^-5M – 8 x 10^-5M); - uma inibição competitiva nas cultivares IAS 55 e Sonora 63 C e uma estimulação na cultivar CNT₁ (faixa de concentração correspondente a 1,6 x 10^-4M – 2,56 x 10^-3M). e) Na presença de alumínio: - não existem diferenças genéticas na absorção (faixa de concentração correspondente a 5 x 10^-6M – 8 x 10^-5M); - existem diferenças genéticas relacionadas ao grau de tolerância ao alumínio (faixa de concentração correspondente a 1,6 x 10^-4M – 2,56 x 10^-3M). f) Na presença do manganês: - existem diferenças genéticas na absorção não relacionadas ao grau de tolerância ao manganês (faixa de concentração correspondente a 5 x 10^-6M – 8 x 10^-5M); - existem diferenças genéticas na absorção não relacionadas ao grau de tolerância ao manganês (faixa de concentração correspondente a 1,6 x 10^-4M – 2,56 x 10^-3M). g) Na cultivar Sonora 63 C a absorção de cálcio é influenciada do mesmo modo pelo alumínio e pelo manganês. 6.5 Absorção de fósforo - a) A absorção de fósforo se realiza através de um único mecanismo. b) Na ausência ou presença de alumínio e de manganês existem diferenças genéticas na absorção do fósforo não relacionadas com o grau de tolerância aos dois elementos. c) O alumínio e o manganês, mais aquele do que este, estimulam a absorção do fósforo.

This research work was carried out aiming the following objectives: a) to identify, in wheat cultivars, the degree of tolerance to aluminum and manganese; b) to evaluate aluminum effect on aereal parts concentrations of calcium, magnesium, and phosphorus from cultivars of wheat with different degree of tolerance to aluminum; c) to evaluate manganese effect on aereal parts concentrations of calcium, magnesium, phosphorus, iron, manganese, zinc and copper, and roots concentrations of calcium, iron and manganese from cultivars of wheat with different degrees of tolerance to manganese; d) to characterize the calcium and phosphorus type of absorption by cultivars of wheat with different degrees of tolerance to aluminum and manganese; e) to evaluate the aluminum and manganese effects on absorption of calcium and phosphorus by cultivars of wheat with different degrees of tolerance to aluminum and manganese. For these purposes, it were carried out two greenhouse experiments, when plants from 30 cultivars of wheat were grown on nutritive solutions containing 0, 2,5, 5,0, 7,5 and 10,0 ppm of aluminum and 0, 8, 16, 24 and 32 ppm of Mn, respectively. In the experiment with increasing levels of aluminum plants were harvested with twelve days of age and the degree of tolerance to aluminum from each cultivar was evaluated through the joint appreciation of aluminum effects, shown by regression analysis, on roots length, roots dry matter weight and aereal parte dry matter weight. In the experiment with increasing levels of manganese plants were harvested seventeen clays of age and the degree of tolerance to manganese was evaluated through appreciation of manganese effects, shown by regression analysis on aereal parts dry matter weight and roots dry matter weight. Phosphorus, calcium and magnesium were determined in the aereal parts of ten wheat cultivars, harvested in the experiment with increasing levels of aluminum and presenting different degrees of tolerance to that element. Phosphorus, calcium, magnesium, iron, manganese, zinc and copper in the aereal parts and calcium, iron and manganese in the roots were determined in six wheat cultivars, whose plants were harvested in the experiment with increasing levels of manganese and presenting different degrees of tolerance to that element. It were run experiments of calcium and phosphorus absorption kinetics, in the presence or absence of aluminum or manganese. This was done with excised roots from 7 day old plants from three cultivars of wheat with differential tolerance to aluminum (Sonora 63 C susteptible; Yecora – intermediate tolerance, and IAS 63 – tolerant), and from three cultivars of wheat with differential tolerance to manganese (CNT₁ - susceptible; Sonora 63 C – intermediate tolerance, and IAS 55 – tolerant). The used experimental solutions had CaCl₂ concentrations of 5x10^-6M, 10^-5M, 2x10^-5M, 4x10^-5M, 8x10^-5M, 1,6x10^-4M 3,2x10^-4M, 6,4x10^-4M, 1,28x10^-3M and 2,56x10^-3M and KII₂PO₄ concentrations of 10^-6M, 1,2x10^-5M, 2,3x10^-5M, 3,4x10^-5M, 4,5x10^-5M, 5,6x10^-5 6,7x10^-5M, 7,8x10^-5M, 8,9x10^-5M and 10^-4M. These solutions were labeled with ⁴⁵Ca and ³²P, respectively. Interpretations were done based on Vm and Km values as parameters, through statistical procedures. The data obtained made possible the following more important conclusions: a) The degree of tolerance to aluminum of wheat cultivars is not related to the aureal parts concentrations of P, Ca, or Mg. b) The degree of tolerance to manganese of wheat cultivars is not related to the aureal parts concentrations of P, Ca, Mg, Fe, Mn, Zn or Cu and to the roots concentrations of Ca, Fe or Mn. c) Ca absorption occurs through two mechanisms. d) Aluminum acts on Ca absorption through: - a competitive inhibition (area of concentration corresponding to 5x10^-6M – 8x10^-5M); - a competitive inhibition on cultivar Sonora 63 C and a stimulus on cultivars IAS 63 and Yecora (area of concentration corresponding to 1,6x10^-4M – 2,56x10^-4M). e) Manganese acts on Ca absorption through: - a competitive inhibition on cultivars Sonora 63 C and CNT₁ and a probably uncompetitive inhibition on cultivars IAS 55 (area of concentration corresponding to 5x10^-6M – 8x10^-5M; - a competitive inhibition on cultivars IAS 55 and Sonora 63 C and a stimulus on cultivars CNT₁ (area of concentration corresponding to 1,6x10^-4M - 2,56x10^-3M). f) In the presence of aluminum: - there are no genetic differences on cal­cium absorption (area of concentration corresponding to 5x10^-6M – 8x10^-5M); - there are genetic differences related to degree of tolerance to aluminum (area of concentration corresponding to 1,6x10^-4M - 2,56x10^-3M). g) Phosphorus absorption occurs through only one mechanism. h) There are genetic differences in the absorption of phosphorus not related to the degree of tolerance to aluminum and manganese either in the absence or presence of both elements. i) Aluminum and manganese more the former than the latter stimulate phosphorus absorption.