Growth, Nodulation and Nitrogen Fixation in Stylosanthes: Effect of Different Root Temperatures at two Shoot Temperatures

Abstract

Nodulated plants of Stylosanthes hamata, S. guianensis, S. humilis, S. scabra and S. fruticosa were grown in controlled environments with varied root and shoot temperatures. Measurement of dry matter and nitrogen content suggested that shoot temperature may be more important than root temperature in controlling growth and nitrogen fixation. There were strong interactions with variety. A fall in relative growth rate with increase in shoot temperature was least for S. guianensis and greatest for S. hamata and S. scabra. The optimum root temperature for growth and nitrogen fixation was approximately 30°C. Ninety percent maximum yield was achieved between root temperatures of 15-36°C for growth and 23-34°C for nitrogen fixation but varied with variety. Nitrogen fixation was more sensitive than dry weight to root temperature. The pattern of response of percentage nitrogen and nitrogen fixation efficiency reflected those for dry weight and nitrogen yields. Shoot to root ratios decreased toward the optimum root temperature then increased at the highest temperature. The reaction of varieties to root and shoot temperatures may be an important factor in determining their suitability for new regions. R. A. Date y D. Ratcliff: Crecimiento, nodulacion y fijacion de nitrogeno en Stylosanthes: efectos de distintas temperaturas de la raiz bajo dos temperaturas del retono. RESUMENSe cultivaron plantas noduladas de Stylosanthes hamata, S. guianensis, S. humilis, S. scabra y S. fruticosa en ambientes controlados con variation de temperaturas de raiz y retono. Las medidas de materia seca y contenido de nitrogeno indican que la temperatura del retono podn'a tener mayor importancia para el control del crecimiento y la fijacion de nitrogeno que la temperatura de la raiz. Se presentaron interacciones fuertes con la variedad. La reduction del ritmo de crecimiento relativo con el aumento de temperatura del retono fue menor para S. guianensis y mayor para S. hamata y S. scabra. La temperatura optima de la rai'z para el crecimiento y fijacion de nitrogeno fue de aproximadamente 30° C. Se logro un rendimiento maximo del 90% entre temperaturas de la raiz de 15-36°C y 23-34°C para fijacion de nitrogeno, pero vario segiin la variedad. La fijacion de nitrogeno resulto mas sensible que el peso seco la temperatura de la rai'z. Los patrones de respuesta del porcentaje de nitrogeno y la eficacia de fijacion de nitrogeno reflejaron los correspondientes al rendimiento de nitrogeno y materia seca. Las relaciones retono.'raiz disminuyeron al aproximarse a la temperatura optima de rai'z y aumentaron bajo la temperatura maxima. La reaction de las variedades a las temperaturas de la rai'z y del retono podri'an ser un factor importante para la determination de su idoneidad para regiones nuevas.

Growth, Nodulation and Nitrogen Fixation in Stylosanthes: Effect of Different Day/Night Root Temperatures

“…Despite differences in plant culture technique between the experiments reported here, where 2.25 litre cylinders were used, and those of Date and Ratcliff (1989), where 60 ml tubes were used the RGRs for growth and nitrogen-fixation at 30/30°C were very similar. The slightly higher values in these Table 8.…”

“…Plants were grown in 2.25 litres of nitrogen-free nutrient solution (Date and Ratcliff, 1989) in cylinders 10 cm in diameter and 30 cm high lined with polyethylene bags. Support for the plants was provided by a polystyrene foam platform fitted into the top of the cylinder to make contact with and float on the nutrient solution.…”

“…Plants were grown at a range of root temperatures but at the same shoot temperature by immersing the cylinders in temperaturecontrolled water baths located in controlled environment cabinets. Seedlings were prepared as described by Date and Ratcliff (1989) and sown at the rate of six per cylinder by inserting the radicles through small holes in the foam platform. All plants (Experiments 1 and 2) were grown initially at 30/30°C day/night root and shoot temperatures for 21 days, under a 14 hour light period with a photosynthetic photon flux density of 280-300 /imol m~2 sec" 1 , before the main temperature treatments were imposed.…”

“…Lawson, S. scabra cv. Seca and S. fruticosa CPI41219A, wholly dependent on symbiotically fixed nitrogen, Date and Ratcliff (1989) have demonstrated that growth and nitrogen fixation are severely restricted at constant root temperatures outside the range 25-35°C. The only other report concerning Stylosanthes (Ranga Rao, 1977a, b) suggests that the best temperature for nodulation of Stylosanthes guianensis and S. humilis is near 27°C and that growth and nitrogen fixation are much reduced at 35°C.…”

Nodulation, Nitrogen Fixation, and Early Growth of Arrowleaf Clover in Response to Root Temperature and Starter Nitrogen

“…Adverse soil temperalures can reduce gemtination and seedling vigor (Evers, 1980) and also can influence the efficiency of the N 2 fixation system (Gibson, 1976), which may further limit legume growth. The response of legumes to root temperature can be influenced by the strain of Rhizobium (Gibson, 1976;Piha and Munns, 1987), shoot temperature (Date and Ratcliff, 1989), and availabili1y of mineral N (La Favre and Eaglesham, 1987). At suboptimal temperatures N 2 fixation is reduced by lower enzyme activities (Gibson, 1966) while at supra-optimal temperatures degeneration of bacteroidal membranes (Pankhurst and Gibson, 1973) and degradation of cytoplasm in cells of stressed nodules (Hemandez-Armenta et al, 1989) decrease N 2 fixation.…”