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In roses (Rosa ×hybrida L.), the bending of branches is a technique that modifies the canopy of the plant and could affect such parameters as the leaf area index (LAI), the quality of reflected light, and the water index (WI) of the plant. The measurement of spectral reflectance with remote sensors is a nondestructive, quick, and simple method to study these parameters. The aim of this paper is to quantify the modification of reflected radiation quality, the LAI and the water index of the plant with different canopies, and its impact on flowering and the number and quality of flowers produced. In R. ×hybrida `Terracotta', using the spectral crop reflectance, the red: far red ratio [red (R) = 680 nm; far red (FR) = 730 nm], percentage of blue light of reflected radiation, and vegetation indices [normalized difference vegetation index (NDVI), simple ratio index (SRI), water index (WI)] were calculated in two architectural managements: traditional (upright hedge) and bent shoot. NDVI had a greater correlation with LAI than SRI (r2 = 0.98 and 0.85, respectively), but SRI was more reliable for LAI values of 1 to 3.5. The bent shoot system compared to the traditional one decreased the R:FR ratio of reflected radiation and increased LAI and plant water content. These changes were related to a higher commercial quality of the flowers (longer flowering shoots with a larger stem diameter and fresh weight), although there was no significant difference in the number of flowers harvested. The period that showed the largest difference in the quality of the flower using the bent shoot system had a LAI of 2.8 vs. 1.8 with traditional management and a marked reduction in the R:FR of the light reflected by bent plants. The bent shoot system advanced the peak production by 1 month at the end of winter and improved the flowers at a time when sun radiation is limiting factor for production.

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Tamaño de contenedor y tipo de sustrato afectan la eficiencia en el uso del agua en Gerbera jamesonii para flor cortada (¹) LIBERTAD MASCARINI (2) ; GABRIEL LORENZO (2) ; HECTOR SVARTZ (2) ; SABRINA PESENTI (2) ; SILVIA AMADO (2) (1) Recebido em 04/02/2010 e aceito para publicação em 09/08/2011.(2) Facultad de Agronomía -Universidad de Buenos Aires. Avenida San Martín 4453 (1417) Ciudad Autónoma de Buenos Aires, Argentina RESUMENSe probaron dos tamaños de contenedor (macetas de 4 y 8 L) y tres mezclas de sustrato (% de turba/perlita 0/100, 25/75 y 50/50) con el objetivo de determinar la combinación óptima para el cultivo de gerbera para flor cortada, considerando la productividad comercial (cantidad y calidad de flores) y el impacto ambiental (eficiencia en el uso del agua y fertilizantes). La mejor combinación en el primer año de producción fue macetas de 8 L con sustrato 0/100, seguido de los contenedores de 4 y 8 L con 25/75, con un rendimiento de 53.4 , 30.5 y 29.7 flores./m-2 respectivamente. El resto de los tratamientos tuvo un rendimiento similar de alrededor de 20 flores m-2. La calidad comercial de las flores cortadas fue aceptable en todos los tratamientos. En cuanto a la eficiencia medida como agua consumida por flor cosechada, el tratamiento 8 L 0/100 resultó claramente superior con un valor de 1.23 L/flor, el resto de los tratamientos estuvieron entre 2.17 y 4.14 L/flor, guardando relación tanto con el tamaño de contenedor como con el tipo de sustrato utilizado. La importancia de estos resultados es la consideración simultánea de los factores que hacen a la rentabilidad comercial y al desarrollo de tecnologías sustentables para los cultivos intensivos. Palabras-chave: agricultura sustentable, cultivo sin suelo, perlita, turba. ABSTRACT Container size and growing media affects water use efficiency in a Gerbera jamesonii cut flower cropTwo containers (4 and 8 L plastic pots) and three growing media mixture types (0/100, 25/75 and 50/50 % of peat/perlite) were used, with the aim of determining the optimum combination for gerbera cut flower crop, considering both commercial productivity (yield and quality of cut flowers) and environmental impact, (water and fertilizer use efficiency). The best combination in the first year of production was 8 L and 0/100, followed of 4 and 8 L with the 25/75, with a yield of 53.4, 30.5 and 29.7 flowers m-2 respectively. The yield of the rest of the treatments were similar, around 20 flowers m-2. Commercial cut flower quality was aceptable in all treatments. Considering the efficiency measured as the ratio water used per flower harvested, 8L 0/100 was clearly superior with a value of 1.23 L/flower, the rest of the treatments were between 2.17 y 4.14 L/flower, keeping relation as much with container size like with growing media mixture. The importance of these results is the simultaneous consideration of many factors which affect both comercial profitability and development of sustainable technology for intensive crops.

Phyto-hormones play a key role in regulating plant responses to stress. Cytokines are a type of phyto-hormones involved in the regulation of many important biological processes related to growth, development, and response to environmental variables. The exogenous application of cytokines increases the possibility of delaying senescence; however, this is a physiological process, and, under certain conditions, degradation processes may be triggered. The effect of 6-bencilaminopurine application and the endogenous hormonal changes involved in lilies floral stalks after their cutting were studied. In order to improve vase life and quality of Lilium longiflorum ‘Brindisi’ flower stalks, they were sprayed with 6-BAP, at a concentration of 300 ppm at pre-harvest, post-harvest, and pre- and post-harvest stages. After that, they were compared to non-sprayed control stalks. The application of 6-BAP caused endogenous hormonal changes in abscisic acid and cytokinin levels, and the most effective treatment was pre-harvest spraying. This treatment proved to be an appropriate method to improve the stalk tolerance to post-harvest stress as it delayed the appearance of senescence symptoms and reduced the speed of chlorophyll degradation with differences of up to 10% with respect to untreated stalks. In addition, the opening of flowers was delayed by up to 2 days, although there were no significant differences in total vase life.