Temporal changes in carboxylate content of ryegrass with stepwise change in nutrition

A detailed scheme of carboxylate formation and retention by plant tissues as a result of ion uptake and utilization is given. By means of discontinuities in the supply with nutrient ions, carboxylate retention by the tissues of perennial ryegrass was followed as a function of growth. It was found that translocation of potassium nitrate to the shoot and subsequent nitrate metabolism was the only process capable of supplying the shoot with sufficient carboxylates and of removing the excess from the foliage to the root system with maintenance of the normal carboxylate content. Absorbed bicarbonate was a good source of carboxylates in the roots, but the rate of translocation to the plant tops was too slow relative to growth. Therefore, the carboxylate concentration in the foliage fell progressively to one half the normal value. Constancy of carboxylate concentration in the dry matter was related to the early establishment of the proportion of carboxylates to dry material in the new growth, making it independent of subsequent changes in water content of the tissues. Changes in carboxylate concentrations due to changes in the supply were continuous with time. Nitrate caused a depression in the roots during nitrate accumulation, but the nitrate metabolism in the follage made sufficient carboxylates available for replenishment and maintenance of their normal level in the whole plant

Temporal changes in carboxylate content of ryegrass with stepwise change in nutrition

A detailed scheme of carboxylate formation and retention by plant tissues as a result of ion uptake and utilization is given. By means of discontinuities in the supply with nutrient ions, carboxylate retention by the tissues of perennial ryegrass was followed as a function of growth. It was found that translocation of potassium nitrate to the shoot and subsequent nitrate metabolism was the only process capable of supplying the shoot with sufficient carboxylates and of removing the excess from the foliage to the root system with maintenance of the normal carboxylate content. Absorbed bicarbonate was a good source of carboxylates in the roots, but the rate of translocation to the plant tops was too slow relative to growth. Therefore, the carboxylate concentration in the foliage fell progressively to one half the normal value. Constancy of carboxylate concentration in the dry matter was related to the early establishment of the proportion of carboxylates to dry material in the new growth, making it independent of subsequent changes in water content of the tissues. Changes in carboxylate concentrations due to changes in the supply were continuous with time. Nitrate caused a depression in the roots during nitrate accumulation, but the nitrate metabolism in the follage made sufficient carboxylates available for replenishment and maintenance of their normal level in the whole plant

Liming influence on soil chemical properties, nutritional status and yield of alfalfa grown in acid soil Influência da calagem nas propriedades químicas do solo, estado nutricional e produção da alfafa em um solo ácido

Alfalfa is an important forage crop with high nutritive value, although highly susceptible to soil acidity. Liming is one of the most efficient and prevailing practices to correct soil acidity and improve alfalfa yield. The objective of this study was to evaluate response to liming of alfalfa grown in a greenhouse on a Typic Quartzipsamment soil. The treatments consisted of four lime rates (0, 3.8, 6.6 and 10.3 Mg ha-1) and two cuts. Alfalfa dry matter increased quadratically with increasing lime rates. In general, dry matter yield was maximized by a lime rate of 8.0 Mg ha-1. Except for the control, the dry matter nutrient contents in the treatments were adequate. The positive linear correlation between root and nodule dry matter with lime rates indicated improvement of these plant traits with decreasing soil acidity. The soil acidity indices pH, base saturation, Ca2+ concentration, Mg2+ concentration, and H + Al were relevant factors in the assessment of alfalfa yield. The magnitude of influence of these soil acidity indices on yield as determined by the coefficient of determination (R²) varied and decreased in the order: base saturation, H + Al, pH, Ca and Mg concentrations. Optimum values of selected soil chemical properties were defined for maximum shoot dry matter; these values can serve as a guideline for alfalfa liming to improve the yield of this forage on acid soils.<br>A alfafa é uma importante forrageira com alto valor nutritivo, porém é altamente suscetível à acidez do solo. A calagem é uma das mais eficientes práticas para corrigir esse problema e melhorar a produtividade da alfafa. O objetivo deste trabalho foi avaliar a resposta à calagem da alfafa cultivada em Neossolo Quartzarênico em casa de vegetação. Os tratamentos consistiram de quatro doses de calcário (0; 3,8; 6,6 e 10,3 Mg ha-1) e duas épocas de corte. A produção de matéria seca foi significativamente aumentada com a adição de calcário, com o máximo rendimento estimado obtido com a adição de 8,0 Mg ha-1. Exceto na testemunha, o teor de nutrientes na matéria seca foi adequado. A matéria seca de raízes e de nódulos foi significativamente aumentada com a aplicação de calcário. Os índices de acidez do solo, como pH, saturação por bases, concentração de Ca2+ e de Mg2+ e H + Al, foram importantes na avaliação do rendimento da alfafa. Magnitudes de influência da acidez do solo desses índices no rendimento variaram, conforme determinado pelo coeficiente de determinação (R²) obedeceram a seguinte ordem decrescente: saturação por bases, H + Al, pH, concentração de Ca2+ e de Mg2+ . Os valores considerados ótimos das propriedades químicas do solo selecionados para obtenção da máxima produção estimada podem servir como referência e melhorar o rendimento de culturas forrageiras em solos ácidos