The influence of different photosynthetically active radiation levels on Ananas comosus (var. erectifolius LB Smith) plants under multiple cropping systems in the upland region of the Guama River, eastern Amazonia

Abstract

Changes in the photosynthetically active radiation (PAR) levels to which a certain species are adapted can result in different plant growth responses. Thus, analytical and systematic studies on the mechanisms that plant species use to survive when subjected to changes in PAR are required. To address the lack of literature on this topic for Ananas comosus, this study aimed to evaluate the effects of different PAR levels on the growth of this species. A completely randomised experimental design was used consisting of subdivided plots containing a total of 1176 forest plants, including 1040 Sc (Schizolobium parahyba subsp. amazonicum), 96 Cg (Cordia goeldiana Huber), 40 Sw (Swietenia macrophylla King), and 13.000 An (Ananas comosus var. erectifolius) agricultural plant species. Seven treatments were established based on this combination of species. These treatments were installed using a completely randomised block design with split plots. Each plot measured 18 m x 24 m, and each treatment was replicated four times, resulting in a total of 28 plots and an experimental area of 12.096 m². After establishing the treatments, studies were conducted to evaluate the influence of different radiation levels on An plant growth. In this study, pluviometric precipitation data and mean percentage values (53, 64, 71 and 100%) of PAR (μmol m -² s -1 ) were recorded. Over the period between 2003 and 2006, the number of leaves, the lengths of the leaves, and the number of An sprouts were measured every six months. The highest number of leaves was recorded in the treatments in which the plants were exposed to 64% PAR. The number of leaves in this treatment was similar to that in the 71% PAR treatment. However, the number of leaves decreased in the plants that were subjected to either the highest (100%) or the lowest (53%) level of PAR. The use of different PAR levels for An plants under cultivation conditions showed that the best growth rates of the leaves and shoots were associated with lower levels of PAR (53% and 64%). However, cultivation under full sunlight favoured a higher number of leaves. The fibre, leaf and mucilage production progressively increased until the third year of the experiment.

Disponibilidade de radiação solar em um sistema agroflorestal composto por >i<Eucalyptus grandis x camaldulensis>/i< e >i<Bixa orellana>/i<

“…Plantas com tais necessidades, alta incidência de radiação solar, são chamadas heliófilas, e em seu ambiente natural de florestas costumam ocupar clareiras ou o topo do dossel (ARMELIN e MANTOVANI, 2001). Dentro das plantas cultivadas na agricultura, grande parte delas necessitam de disponibilidade de radiação acima de 50% (EL-BASSIONY et al;CORDEIRO et al;2016). Nesse experimento os níveis de radiação foram próximos aos 50% ou inferiores.…”

“…No cafeeiro é a sombra provoca um limite de saturação entorno de 300 µmol de fótons m-2 s-1 e se não for sombreado torna-se acima de 600 µmol fótons m-2 s-1 (KUMAR TIESZEN, 1980). Cordeiro et al (2016) em estudo com abacaxizeiro observou valores entre 53 e 67% como limite de saturação. Em contrapartida, outras espécies adaptaram-se bem a ambiente com alta incidência de radiação e não demonstram quedas de produção.…”

“…Entretanto, algumas espécies não possuem esse comportamento. Como para o cafeeiro que absorve 50% da radiação (RIGHI et al 2007); o tomateiro com cerca de 50% (EL-BASSIONY et al 2014) e o abacaxizeiro, entre 53 a 64% da radiação disponível (CORDEIRO et al 2016). Por tanto, determinar até que ponto um vegetal absorve eficientemente a radiação solar é essencial para se avançar na determinação da composição dos SAFs e assim difundir sua adoção.…”

“…Merr.) foi constatado que o vegetal não suporta mais que 53 a 64% da RFA, demostrando grande sensibilidade ao excesso de luz(CORDEIRO et al, 2016). Outros autores ainda demonstraram que mesmo as culturas respondendo de forma negativa ao sombreamento, ganhos em teor de proteína foram observados(ARTRU et al, 2016).…”