Adaptações fisiológicas e anatômicas de melissa officinalis L. (Lamiaceae) cultivadas sob malhas termorrefletoras em diferentes intensidades luminosas / Physiological and morphological adaptations of melissa officinalis L. (Lamiaceae) cultivated under thermo-reflector shading nets at different luminous intensities

Objetivou-se, com a realização da pesquisa, avaliar modificações fisiológicas e anatômicas em plantas de melissa, cultivadas sob malhas termorrefletoras (Aluminet®), em diferentes níveis de sombreamento, visando conhecer a plasticidade fenotípica em resposta de adaptação a diferentes quantidades de luz. Os tratamentos foram caracterizados por plantas submetidas a pleno sol e a 20 e 60 por cento de intensidade luminosa, e arranjados conforme o delineamento inteiramente casualizado (DIC). As quantificações de clorofila foram feitas em quatro repetições, as medições das epidermes e parênquimas foram repetidas 15 vezes e utilizou-se 10 repetições para as avaliações das características de cloroplastos e grãos de amido destes. Plantas submetidas a 20 por cento de intensidade luminosa apresentaram maior quantidade de clorofila a e, portanto, maior razão clorofila a/b. Comparativamente, as folhas de melissa a pleno sol e a 60 por cento de luz apresentaram células da epiderme adaxial mais espessas, mas as células da epiderme abaxial mostraram características encontradas em folhas de sombra, ou seja, mais finas. Quanto maior a intensidade luminosa, maior o número de cloroplastos, porém, a pleno sol mostraram-se mais finos e com menor área. Os grãos de amido de plantas cultivadas sob ambientes sombreados tiveram maior área e ocuparam maior parte nos cloroplastos de plantas a 60 por cento de intensidade luminosa. Assim, plantas de melissa, quando submetidas ao sombreamento, tiveram plasticidade fenotípica.

The aim of this study was to evaluate physiological and anatomical modifications in lemon balm plants, cultivated under thermo-reflector nets (Aluminet®) at different levels of shading, in order to understand the phenotypic plasticity in adaptation response to different light quantities. The treatments were characterized by plants subjected to full sun and 20 and 60 percent of luminous intensity, and arranged in completely randomized design (CRD). The quantifications of chlorophylls were done in four replicates, the measurements of epidermis and parenchymas were repeated 15 times and 10 replicates were used to evaluate characteristics of chloroplasts and their starch grains. Plants subjected to 20 percent of luminous intensity showed higher quantity of chlorophyll a and, therefore, higher chlorophyll a/b ratio. Lemon balm leaves under full sun and 60 percent of light showed thicker adaxial epidermis cells, but the abaxial epidermis cells showed characteristics found in shaded leaves, i.e., they were slender. The higher the light intensity, the larger the number of chloroplasts; however, under full sun, they were slender and had smaller area. The starch grains of leaves grown under shaded environments showed larger area and, at 60 percent of luminous intensity, occupied the largest part of chloroplasts. Thus, lemon balm plants, subjected to shading conditions, showed phenotypic plasticity.

Fine structural study of the red seaweed Gymnogongrus torulosus (Phyllophoraceae, Rhodophyta)

The present study analyzed several characters of the red seaweed Gymnogongrus torulosus, such as cellular structure of the thallus, cuticle, pit plug and cell wall ultrastructure, and morphology of some organelles like plastids, Golgi bodies and mitochondria. Also, anomalous chloroplasts with thylakoid disorganization were found in medullary cells. The significance of this thylakoid disposition is still unclear. This is one of the first studies focused on the fine structure of a red alga recorded in Argentina.