Abstract
ABSTRACT Conventional soil and hydroponic growing systems have inherent differences in water and nutritional availability. These differences may affect plant physiological development and biochemistry. The objective of this study was to evaluate lettuce (Lactica sativa) cv. ‘Crocantela’development in either a hydroponic system or in soil through analyses of vegetative growth; chlorophyll abundance; and sugar and starch content. We evaluated the dry mass (DM), fresh mass (FM), number of leaves (LN), stomatal density and contents of chlorophyll, carotenoids, sugars and starch. Due to the improved nutritional conditions, especially in relation to macronutrients, plants grown in hydroponic system presented significant differences in chlorophyll a (0.4481 mg/g), b (0.1233 mg/g) and total chlorophyll content (0.5714 mg/g), as well as greater biomass when compared to plants cultivated in pots (FM: 342.69 g; DM: 21.13 g; NL: 17.75 g). The lower water availability for plants cultivated in pots influenced the increase in carbohydrate concentration and stomatal density in leaves (adaxial: 45.83 stomates/mm2; abaxial: 64.75 stomates/mm2) of lettuce plants.
Highlights
As plantas cultivadas em sistemas a campo e em hidroponia apresentam grandes diferenças em relação a disponibilidade hídrica e nutricional, afetando o ciclo de desenvolvimento e metabólico, a anatomia dos órgãos e o desempenho das plantas devido a mudanças no comportamento fisiológico e bioquímico
Plants were placed in several lines, 0.25 m apart, between plants and lines; distances were equal under either soil or hydroponic systems, with density of 16 plants per m2
Plants grown in hydroponics showed several parameters significantly higher than plants grown in soil: LR (69.8%); aerial height (AH) (115%); TPH (85.2%); leaf number (LN) (104.7%); fresh root mass (FRM) (319.9%); fresh aerial mass (FAM) (767.6%); TFM (678.5%); dry aerial matter (DAM) (75.2%); TDM (71.37%), and TFM/TDM (365%), with values in percentages reflecting how much greater mean values were in hydroponic-grown plants than in pot-grown ones (Table 2)
Summary
As plantas cultivadas em sistemas a campo e em hidroponia apresentam grandes diferenças em relação a disponibilidade hídrica e nutricional, afetando o ciclo de desenvolvimento e metabólico, a anatomia dos órgãos e o desempenho das plantas devido a mudanças no comportamento fisiológico e bioquímico. There are at least four widely-used systems for lettuce cultivation: conventional and organic farming in open field; hydroponic cultivation in a controlled environment; and soil cultivation in greenhouses. These four systems differ in both environment and post-production handling of the harvested lettuce (Henz & Suinaga, 2009). Bras., Brasília, v.37, n.1, January-March 2019 and precipitation, lead to subsequent variations of the product’s quality, as well as to added risk of pests and pathogens incidence (Grillas et al, 2001) Long drought periods, such as the one that took place in Brazil during the summer 2014, may result in losses of both quantity and quality; excess heat can burn leaves and roots, and water deficit can lead to poor plant health and increase the susceptibility to disease (Reetz et al, 2014)
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