Sombreamento de plantas de Catharanthus roseus (L.) G. Don 'Pacifica White' por malhas coloridas: desenvolvimento vegetativo

Abstract

RESUMOAs malhas coloridas têm sido utilizadas para manipular o desenvolvimento vegetativo, melhorando a utilização da radiação solar por plantas ornamentais. Objetivou-se, neste trabalho estudar o efeito da redução de 50% da radiação fotossinteticamente ativa sobre o crescimento vegetativo de plantas de Catharanthus roseus (L.) G. Don, por meio de malhas azul e vermelha e malha preta, em comparação com plantas crescidas na ausência de sombreamento (pleno sol). As plantas foram obtidas a partir de sementes e tratadas por 180 dias. Foram avaliados o ganho de biomassa e a distribuição de matéria seca nas plantas, o conteúdo de pigmentos foliares (clorofilas e carotenóides) e de nitrogênio foliar. A malha vermelha provocou um aumento de matéria seca total e de área foliar das plantas em comparação com as malhas azul, preta e ao tratamento a pleno sol, porém, exceto em relação a esse tratamento, a malha vermelha causou menor conteúdo de nitrogênio e pigmentos foliares. A maior relação raiz/parte aérea e relação clorofila a/b, menores razões de área foliar e de massa foliar das plantas crescidas a pleno sol em relação às plantas sombreadas indicam um efeito mais proeminente da irradiância mais alta do que da alteração do espectro de luz. O sombreamento altera significativamente a distribuição de matéria seca e o uso de malhas de diferentes cores modifica o conteúdo de pigmentos fotossintéticos dessa espécie.Termos para indexação: Vinca, área foliar, distribuição espectral, matéria seca, carotenóides, clorofilas, Catharanthus roseus. ABSTRACTColored shade nets have been used to manipulate the vegetative development, improving the utilization of solar radiation by ornamental plants. This work aimed to study the effect of 50% reduction of PAR on vegetative growth of plants of Catharanthus roseus (L.) G. Don, using blue and red nets, and black net, in comparison to plants growing under full sunlight (lack of shading). The plants were obtained from seeds and treated for 180 days. Biomass increment and distribution, pigment content (chlorophylls and carotenoids) and foliar nitrogen were evaluated. The red net caused an increase of total dry mass and total leaf area of plants when compared to the blue net, black net and the full sunlight treatment, however, except in relation to the last treatment, the red net caused lower contents of foliar nitrogen and pigments. The higher root/stem and chlorophyll a/b ratios and the lower leaf area and leaf dry mass of plants growing under full sunlight in relation to shaded plants indicate a more prominent effect of the higher irradiance than the spectral alteration. Shading alters significantly the dry matter distribution and the use of shade nets of different colors affects the content of photosynthetic pigments of this species.

Incidence of arthropods and phytotechnical characteristics of lisianthus under different greenhouse conditions

“…The black and blue meshes caused lower performance in the weight of flowers. Melo and Alvarenga (2009) observed similar results to the present study in vinca plants (Catharanthus roseus), with total dry matter increase and leaf area under red mesh compared to blue and black meshes and treatment in full sun. The authors attributed this increment of total dry mass to the lower red/far-red ratio, provided by the red shading mesh.…”

Photosynthetic behavior, growth and essential oil production of Melissa officinalis L. cultivated under colored shade nets

“…Better plant growth using red net was also observed in Catharanthus roseus (L.) G. Don (Melo and Alvarenga, 2009). The leaves of plants grown under red net may have benefited by the greater availability of red radiation (above 590 nm), which is more efficient for the performance of photochemical step of photosynthesis (Henrique et al, 2011).…”

Initial growth of sweet pepper in different substrates and light environments

“…The total dry mass did not differ between Alu-minet®, red and black screens, but these values differed from that obtained in the control, where a lower dry mass was obtained. Melo & Alvarenga (2009) obtained higher total dry mass of Catharanthus roseus when grown under a red screen, according to the authors, the distribution of dry mass between the different organs of a plant is a behavior of plant species themselves and demonstrates their adaptation to the different environment conditions. The root dry mass was higher in the seedlings grown under black screen, differing from the other treatments, where the full sun provided a lower root dry mass (Table 6).…”

“…The red screen increases the light transmittance of the spectrum in far-red and red waves (Corrêa et al, 2012). In response to the far-red/red ratio, the plants increase the elongation rate of stems and petioles (Melo & Alvarenga, 2009).…”