Crecimiento secundario inusual en raíz principal de Pfaffia gnaphalioides (L. Fil.) Mart. (Amaranthaceae)

Abstract

RESUMEN -(Crecimiento secundario inusual en raíz principal de Pfaffia gnaphalioides (L. Fil.) Mart. (Amaranthaceae)). Raíces de Pfaffia se comercializan como "ginseng brasilero" y extractos crudos de raíces de Pfaffia glomerata tienen actividad analgésica y desinflamatoria. Pfaffia gnaphalioides es herbácea perenne y crece en el área serrana del sur de la Provincia de Córdoba, Argentina. El objetivo de este trabajo es estudiar el crecimiento secundario inusual en raíz principal de Pfaffia gnaphalioides. Se estudió en invernáculo la forma de crecimiento durante los dos primeros años relacionando la parte aérea y subterránea. Se realizaron calicatas in situ para analizar el sistema radical. La raíz principal desarrolla raíces laterales, plagiótropas, con yemas que forman brotes aéreos de innovación. En cortes transversales de raíz principal se observa desarrollo secundario inusual. Un meristema lateral produce corteza secundaria hacia afuera y tejido conjuntivo y una sucesión de cambia vascular hacia adentro. Cuando cada cambium vascular es producido, el meristema lateral que se encuentra hacia afuera de éste tiende a permanecer quiescente, retornando a la actividad cuando el cambium vascular interno a éste permanece menos activo. Los cordones vasculares secundarios están dispuestos en anillos concéntricos sin radios parenquimáticos. La presencia de abundante parénquima conteniendo almidón en la estructura inusual de raíz en Pfaffia gnaphalioides, constituye una buena adaptación a condiciones xéricas. Palabras claves:Pfaffia gnaphalioides, Amaranthaceae, raíces gemíferas, cambia adicionales, lateral meristem ABSTRACT -(Secondary and unusual growth in main root of Pfaffia gnaphalioides (L. Fil.) Mart. (Amaranthaceae)). Pfaffia roots have been commercialized as "brazilian ginseng" and crude extracts of Pfaffia glomerata roots have analgesic and disinflamatory activity. Pfaffia gnaphalioides is a perennial herb and grows in southern Córdoba, Argentina. The objective of this work is to analyze root systems in Pfaffia gnaphalioides. Growth of above and belowground organs was observed for two years in a greenhouse. Belowground organs were analyzed in situ in hillcountry shrublands, by digging soil pits. The root system is characterized by presence of a main root and superficial plagiotropic lateral roots. Lateral roots show renewal buds that give rise to new aerial innovation shoots. Unusual secondary growth is observed in the main root. A lateral meristem produces secondary cortex to the outside and conjuntive tissue and a succesion of vascular cambia to the inside. As each vascular cambium is produced, the lateral meristem outside it tends to become quiescent, returning to activity when the vascular cambium internal to it has become less active. Secondary vascular strands are arranged in concentric rings without rays. The presence of abundant parenchyma containing starch in unusual structure of Pfaffia gnaphalioides, constitutes an adaptation to xeric conditions.

Chemical Structure and Localization of Levan, the Predominant Fructan Type in Underground Systems of Gomphrena marginata (Amaranthaceae)

“…The secondary structures of roots and stems observed in G. marginata show an unusual or anomalous thickening of the vascular cylinder due to the high activity of supernumerary cambia, resulting specially in the formation of abundant reserve tissues. This anomalous thickening is a common phenomenon in the Amaranthaceae (Metcalfe and Chalk, 1950; Menezes et al, 1969; Grosso, 2007; El-Ghamery et al, 2015; Sá et al, 2016) and Chenopodiaceae (Metcalfe and Chalk, 1950; Krumbiegel, 1998). In G. albiflora , root secondary growth was also considered atypical (Jáuregui et al, 2014) as the authors showed that the successive rings are formed from a lateral meristem producing parenchyma outward, supernumerary cambia and parenchyma inward.…”

“…The underground reserve system of G. marginata is mainly a tuberous root, capable of resprouting due to the presence of buds, also described in Pfaffia gnaphalioides (Grosso, 2007) and in tuberous roots of Vernonia brevifolia (currently Lessingianthus brevifolius ) (Hayashi and Appezzato-da-Glória, 2007) and V. oxylepis (Vilhalva and Appezzato-da-Glória, 2006), both inulin accumulating Asteraceae species. The presence of buds in belowground organs allows the regeneration of the aerial parts after drought, fire or any other environmental disturbance (Klimesová and Klimes, 2007), while the reserve compounds therein supplies energy and carbon to guarantee resprouting, growth, and ultimately, species survival.…”

Anatomia de raízes e caules de Bignonieae: síndrome lianescente e xilema secundário

“…Apesar de comuns em caules de diversas espécies de lianas, principalmente por sua conexão com o hábito, as variações cambiais ocorrem também nas raízes, de forma semelhante aos caules, em vários grupos de plantas, como Amaranthaceae, Basellaceae, Nyctaginaceae, Passifloraceae, Phytolaccaceae, Polygonaceae e Sapindaceae (Grosso 2007;Rajput et al, 2010;El-Ghamery et al 2015;Carlquist 1999;Carlquist 2004;Hearn 2009;Mikesell 1979;Horak 1981;Rajput 2015). Os trabalhos de Gabrielli (1992), Martinelli et al (2008) e Singh & Misra (2012) demonstram que também as raízes de espécies de Bignonieae desenvolvem cunhas de floema semelhantes às encontradas em caules, entretanto esses estudos se mostram rasos ou incompletos quanto a maiores aspectos anatômicos e estruturais.…”