EFFECT OF NITROGEN ON SAFFLOWER PHYSIOLOGY AND PRODUCTIVITY

Safflower ( Carthamus tinctorius ) L. is an oil-crop suitable for semi-arid agriculture, but its physiological re- sponse to agronomic inputs has yet to be fully evaluated. The effect of fertiliser on the physiology and produc- tion of Safflower grown in pots filled with standard grade perlite inside a semi-controlled glass house was studied. Plants were initially irrigated with 20-100 ml standard hydroponic solution and then one month after germination plants were irrigated using 50-200 ml complete Hoagland\u2019s solution, supplemented with one of eight levels of nitrogen (0, 25, 50, 75, 100, 125, 150, 175 kg N ha-1) in the form of ammonium nitrate. Elevating nitrogen to 100 kg N ha-1 significantly increased the assimilation rate by about 42 %, transpiration rate by 32%, stomatal conductance by 52% and LAI by 42% compared with the control. The above ground dry weight, seed yield and Water Use Efficiency (WUE) increased incrementally with increases in nitrogen rate. Above ground dry weight increased by an average of 42%, seed yield by 76% and WUE by 41% at harvest compared with the control. This study clearly demonstrates how nitrogen fertilisation can affect physiology of Safflower leading to im- provement in seed yield.Le carthame ( Carthamus tinctorius ) L.) est une culture ol\ue9agineuse appropri\ue9e \ue0 l\u2019agriculture semi aride, mais sa r\ue9ponse physiologique aux intrants agronomiques reste \ue0 \ue9valuer. L\u2019effet de fertilisants sur la physiologie et la production du carthame cultiv\ue9 en pots rempli de perlites de niveau standard \ue0 l\u2019int\ue9rieur d\u2019une serre semi contr\uf4l\ue9e \ue9tait \ue9tudi\ue9. Les plants \ue9taient initialement irrigu\ue9s avec 20-100 ml de solution hydroponique standard et, ensuite, un mois apr\ue8s la germination des plants \ue9taient irrigu\ue9s avec 50-200 ml de solution de Hoagland compl\ue8te et un suppl\ue9ment de huit niveau d\u2019azote (0, 25, 50, 75, 100, 125, 150, 175 kg N ha-1) sous forme du nitrate d\u2019ammonium. L\u2019utilisation de la dose de 100 kg N ha-1 a significativement accru le taux d\u2019assimilation d\u2019environ 42 %, le taux de transpiration de 32 %, la conductance stomatale de 52 % et l\u2019index de la surface foliaire de 42 % en comparaison avec le t\ue9moin. Le poids sec de la biomasse a\ue9rienne, le rendement en grain et le Water Use Efficieny (WUE) avait augment\ue9 avec la dose d\u2019azote. Le poids sec de la biomasse a\ue9rienne a en moyenne augment\ue9 de 42% pendant que le rendement en grains et le WAE ont augment\ue9 \ue0 la r\ue9colte de 76% et 41% , respectivement, en comparaison avec le t\ue9moin. Cette \ue9tude d\ue9montre clairement comment la fertilisation azot\ue9e peut affecter la physiologie du carthame conduisant \ue0 l\u2019am\ue9lioration du rendement en grains

Interactive effects of light, leaf temperature, CO 2 and O 2 on photosynthesis in soybean

A biochemical model of C 3 photosynthesis has been developed by G.D. Farquhar et al. (1980, Planta 149, 78–90) based on Michaelis-Menten kinetics of ribulose-1,5-bisphosphate (RuBP) carboxylase-oxygenase, with a potential RuBP limitation imposed via the Calvin cycle and rates of electron transport. The model presented here is slightly modified so that parameters may be estimated from whole-leaf gas-exchange measurements. Carbon-dioxide response curves of net photosynthesis obtained using soybean plants ( Glycine max (L.) Merr.) at four partial pressures of oxygen and five leaf temperatures are presented, and a method for estimating the kinetic parameters of RuBP carboxylase-oxygenase, as manifested in vivo, is discussed. The kinetic parameters so obtained compare well with kinetic parameters obtained in vitro, and the model fits to the measured data give r 2 values ranging from 0.87 to 0.98. In addition, equations developed by J.D. Tenhunen et al. (1976, Oecologia 26, 89–100, 101–109) to describe the light and temperature responses of measured CO 2 -saturated photosynthetic rates are applied to data collected on soybean. Combining these equations with those describing the kinetics of RuBP carboxylase-oxygenase allows one to model successfully the interactive effects of incident irradiance, leaf temperature, CO 2 and O 2 on whole-leaf photosynthesis. This analytical model may become a useful tool for plant ecologists interested in comparing photosynthetic responses of different C 3 plants or of a single species grown in contrasting environments.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/47469/1/425_2004_Article_BF00395048.pd

Anatomical and physiological characteristics of two argentine wheat cultivars Características anatômicas e fisiológicas de dois cultivares argentinos de trigo

Two Argentine field grown wheat cultivars (Triticum aestivum L.), Buck Cencerro (BC) with traditional germoplasm, and Buck Pucará (BP) with Mexican germoplasm, have been investigated in order to compare anatomical and physiological characteristics of the flag leaf measured in heading (stage E59), anthesis (stage E69) and kernel water ripe (stage 71). In both cultivars, photosynthetic rate was not different for the same phenological stage, except for E71. Averages in stage E59 were higher than stages E69 and E71 for both cultivars (22.70, 18.40 and 10.40 µmol m-2 s-1 for BP and 23.82, 18.41 and 8.28 µmol m-2 s-1 for BC, respectively). Transpiration rates were higher in BP (5.0, 5.6 and 4.89 mmol m-2 s-1) than BC (3.3, 4.4 and 2.57 mmol m-2 s-1) for stages E59, E69 and E71, respectively. Consequently, instantaneous water use efficiencies were higher in BC than in BP. No difference between cultivars and phenological stages was observed in specific surface area (mesophyll area per unit mass) determined by physical adsorption of nitrogen at low temperature (78&deg; K); the mean was 8.9 m² g-1. It was similar as values found in previous works, in others T. aestivum L. and greater than the values found for Ligustrum lucidum Aiton, by the same technique. Differences could be attributed to the roughness of the cell wall and the dimensions of the cell itself. No positive correlation between specific surface and photosynthetic rate was observed neither for cultivars nor for phenological stages.<br>Dois cultivares argentinos de trigo (Triticum aestivium L), Buck Cencerro (BC), com germoplasma tradicional e Buck Pucará (BP), com germoplasma mexicano, foram pesquisados para comparar as características anatômicas e fisiológicas da folha bandeira medida no espigamento (estádio E59), na antese (estádio E69) e na fase de grão aquoso completo (estádio E71). Nos dois cultivares, a taxa fotossintética foi semelhante no mesmo estágio fenológico, exceto no E71. As médias no estádio E59 foram superiores às dos estágios E69 e E71 nos dois cultivares (22,70; 18,40 e 10,40 µmol m-2 s-1 para o BP e 23,82; 18,41 e 8,28 µmol m-2 s-1 para o BC, respectivamente). Nos três estádios, as taxas de transpiração foram maiores no BP (5,0; 5,6 e 4,89 mmol m-2 s-1) comparado ao BC (3,3; 4,4 e 2,57 mmol m-2 s-1). Consequentemente, a eficiência de uso instantâneo de água foi maior no BC, quando comparado com o BP. Não foram observadas diferenças de área foliar específica para cultivares e estádios fenológicos (área do mesófilo por unidade de massa), determinada por adsorção física de nitrogênio a baixa temperatura (78&deg; K), registrando-se média geral de 8,9 m² g-1. Esse valor foi semelhante a outros reportados em trabalhos prévios com T. aestivum L. e maiores que os determinados para Ligustrum lucidum Aiton, pela mesma técnica. As diferenças podem ser atribuídas à rugosidade da parede celular e as próprias dimensões da célula. Não houve correlação positiva entre área específica e taxa fotossintética para cultivares ou estádios fenológicos