Tomatoes that will last for one month or more at tropical temperatures, without refrigeration, are now feasible. Attention has been given to major genes which drastically modify the ripening process. ...When these genes are homozygous, tomatoes do not develop fuU color and may not soften for months. In the heterozygous state, as would be found in hybrid tomatoes, these genes result in red tomatoes with extended shelf life. A search was made for genes that increase shelf life without drastic effects. Six sources of long-life were crossed to a conventional tomato cultivar and shelf life was measured in F 1, F2, F3 and DCgenerations. In each generation shelf lives were shorter than those of the long-lived parent, and usually as short or shorter than the mean of the two parents. A few segregants with exceptionally long shelf life were obtained. The results suggest that a relatively few genes are segragating and that these can be transferred to more suitable varieties to achieve long lasting tomatoes in pure lines. --- Ya es factible lograr tomates que puedon dura un mes 0 mas a unas temperaturas tropicales, sin refrigeracidn, Se ha enfocados en algunos genes principales que modifican radicalmente el proceso de maduracion, Cuando estos genes son homocigdncos, el color de los tombtes no se desarrolla plenamente y los frutos pueden tardar unos moses en ablandarse. En el estado heterocig6tico, como el que puede observarso en los tomates hibridos, estos genes producen tomates rojos con una vida de almaconaje mas extendida, Se bused los genes que extiendon la vida de almacenajo sin producir otros efectas graves. Se cruz6 seis especies duraderas con un cultivar de tomate tradicional y se calculo' la vida de almacenaje para las generaciones Fl, F2, F3 Y BC. Para cada generacidn, la vida de almacenaje era mas corta que la de la planta madre mas duradera; en la mayorfa de los casos, era tan codta 0 mas corta que la vida promedia de las dos plantas madres, Se obtuvo algunos elementos segregados con una vida de almacenaje excepcionalmente larga, Los resultados hacen creer que existen unos pocos genes segregantes y que estes se pueden trasladar a unas especies mas convenientes, afin de lograr tomates duraderas en las especies puras.
Tomato fruit setting on high density defoliated tomato plants with similar leaf area index was determined in three environmental conditions, inside polyethylene tunnels. Experiment 1 was carried out ...in autumn when average solar radiation received by the crop was 8.0 MJ m-2 day-1. Average external temperature was 18.1ºC. Experiments 2 and 3 were conducted in spring, when average external temperature was 19.7ºC. In experiment 2, average solar radiation received by the crop was 12.4 MJ m-2 day-1, whereas in experiment 3 it was reduced to 5.9 MJ m-2 day-1 by a 52% shading net. Plants were grown in bags, spaced 1.0 m between row and 0.3 m within row bags distance, using 5.5 L of a commercial substrate. Nutrients and water were supplied by means of a nutrient solution, delivered daily in order to replace volumes lost by transpiration. Treatments consisted of one (T1), two (T2) and three (T3) plants per bag, leading to plant densities of 3.3, 6.7 and 10 plants m-2, respectively. In T1, three leaves per sympod were kept, with a ratio of 3:1 between number of leaves and inflorescences per sympod. In T2, two and one leaf was kept respectively on two consecutive sympods, alternatively on both plants. The ratio between number of leaves and inflorescences was 3:2. In T3, with three plants per bag, only one leaf per sympod was kept on each plant. The ratio between number of leaves and inflorescences was 3:3. In all experiments, the number of trusses per area in T2 and T3 was two and three times higher than in T1, respectively. The number of fruits per unit ground area was lower in T1 plants and similar in T2 and T3 plants in the first experiment, whereas in the second and third experiments similar values were observed among treatments. Results indicated that tomato plants adjust the number of fruits, and exceeding flowers are aborted. The use of a plant density of 6.7 plants m-2 combined with a 3:2 ratio between number of leaves and inflorescences per unit ground area seems to be the upper limit in maximizing the number of set fruits of this crop.
O número de frutos em plantas de tomateiro cultivadas em alta densidade e com índice de área foliar similar mantido através de desfolhamento foi determinado em três condições ambientais, no interior de túneis de polietileno. O experimento 1 foi conduzido no outono, com radiação solar média recebida pela cultura de 8,0 MJ m-2 dia-1 e temperatura média exterior de 18,1ºC. Os experimentos 2 e 3 foram conduzidos na primavera, com temperatura média exterior de 19,7ºC. No experimento 2, a radiação solar média recebida pela cultura foi de 12,4 MJ m-2 dia-1, enquanto no experimento 3 foi reduzida para 5,9 MJ m-2 dia-1 por meio de uma tela com 52% de sombreamento. As plantas foram cultivadas em sacolas, com 1,0 m entre fileiras e 0,3 m entre sacolas, enchidas com 5,5 L de substrato comercial. Nutrientes e água foram fornecidos via solução nutritiva, de forma a repor os volumes perdidos pela transpiração. Os tratamentos consistiram de uma (T1), duas (T2) e três (T3) plantas por sacola, correspondendo a densidades de 3,3; 6,7 e 10 plantas m-2, respectivamente. Em T1, três folhas por simpódio foram mantidas, com uma proporção de 3:1 entre o número de folhas e de inflorescências, em cada simpódio. Em T2, duas e uma folha foram mantidas respectivamente em dois simpódios consecutivos, alternativamente em ambas as plantas da sacola. A relação entre o número de folhas e de inflorescências foi de 3:2. Em T3, com três plantas por sacola, somente uma folha por simpódio foi mantida, com uma relação de 3:3. Em todos os experimentos, o número de inflorescências por unidade de área em T2 e T3 foi duas e três vezes maior que em T1, respectivamente. O número de frutos fixados por área de solo foi menor em T1 e similar em T2 e T3 no primeiro experimento, enquanto no segundo e terceiro experimentos valores similares foram observados entre os tratamentos. Os resultados indicaram que as plantas de tomateiro ajustam o número de frutos fixados e as flores excedentes são abortadas. Uma densidade de 6,7 plantas m-2 combinada com uma proporção de 3:2 entre o número de folhas e de inflorescências por unidade de área de solo é apontada como a mais indicada para maximizar a fixação de frutos da cultura.
The influence of light-on and light-off on nitrate reduction in leaves of tomato plants (Lycopersicum esculentum) grown on nutrient solution was measured in various ways. Nitrate reductase activity ...was measured both in vivo and in vitro and actual nitrate reduction was calculated from the nitrate flux to the leaves and the nitrate content of the leaves. In addition the metabolic pool of nitrate was measured.
After light-on in vitro nitrate reductase activity, nitrate flux and metabolic pool of nitrate increased and somewhat later actual nitrate reduction as well. In vivo nitrate reductase activity was not influenced to any extent. At the end of the light period nitrate flux to the leaf and actual nitrate reduction were approximately equal. After light-off both nitrate flux and metabolic pool of nitrate decreased. Nitrate reduction continued for at least one hour in the dark.
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