Measurements Of 14c Incorporation By Illuminated Intact Leaves Of Coffee Plants From Gas Mixtures Containing 14co2

A study was made of the incorporation of 14C by intact leaves of Coffea arabica (cultivars Mundo Novo, Catuai, 1130-13, and H 6586-2) and Coffea canephora (cultivar Guarini) supplied with gas mixtures containing 14CO2 under controlled conditions. Samples of the leaves were combusted and the 14C in the CO2 produced measured using a liquid scintillation counter. The results were used to estimate photosynthetic rates. The effects of changing the partial pressures of O2 and CO2 on the photosynthetic rate were studied and estimates made of the CO2 compensation point and photorespiration.The data obtained show differences between the mean net photosynthetic rates of the C. arabica cultivars (6·14 mg CO2 dm-2 h-1) and the mean rate for the C. canephora cultivar (3·96 mg CO2 dm-2 h-1). The cultivar of the latter species photorespired more rapidly than the cultivar Catuai of C. arabica. Rates of photosynthesis in coffee measured using the 14CO2 method were similar to rates obtained by others using an infrared gas analyser. The 14CO2 method proved to be reliable for photosynthetic measurements and the apparatus is suitable for use in field conditions. © 1976 Oxford University Press.2761187119

Caracterização isoenzimática de clones e somaclones de cana-de-açúcar Isoenzymatic characterization of sugarcane clones and somaclones

Foram caracterizados os padrões de isoenzimas de peroxidase e esterase de extrato de folha e raiz de cana-de-açúcar de variedade e somaclones de NA56-79 aos 7 meses de idade e de variedades e somaclones de NA56-79, IAC68-12 e IAC68-144 aos 9 meses. Avaliaram-se também as atividades específicas de peroxidase com relação ao tempo e perfil isoenzimático das três variedades e respectivos somaclones. Os zimogramas de peroxidase e esterase de folhas mostraram diferenças distintas entre as três variedades; a esterase apresentou menor número de bandas em relação à peroxidase, porém de mais fácil caracterização. Os zimogramas de raízes, devido à grande variação de atividade enzimática, em conseqüência de raízes velhas, não foram conclusivos quanto à identificação das variedades. Não ocorreram diferenças nos zimogramas de peroxidase ou esterase entre somaclones da mesma variedade. NA56-79 apresentou menor número de isoenzimas e menor atividade especifica de peroxidase em relação à IAC68-144, sugerindo que a diminuição das isoenzimas seja associada ao decréscimo de atividade enzimática. A atividade especifica de peroxidase variou com a maturação, sendo a 9 meses maior do que a 7.<br>Extracts from leaves and roots of three sugarcane varieties and their somaclones: NA56-79 (at seven and nine month old plants), IAC68-12 and IAC68-144 (both at nine month old plants) were obtained. The peroxidase and esterase isoenzyme contents of the extracts were determined to verify the genetic variability of tissue culture somaclones. The peroxidase specific activity was studied in relation to the time and isoenzymatic pattern. The peroxidase and esterase zymograms showed distinct differences among varieties, and the esterase presented less bands but easier to characterize than the peroxidase bands. The root zymograms exhibited great enzymatic variation due to the presence of old roots thus not allowing to characterize the varieties. No differences in peroxidase or esterase zymograms among somaclones of the same variety were noticed. The NA56-79 presented lower specific activity of peroxidase and number of isoenzymes than IAC68-144, suggesting that the decrease of isoenzyme bands is associated to the reduction of enzymatic activity. The specific activity of peroxidase changed with maturity and was higher at nine than at seven month old plants