ABSTRACT
RESUMEN Talinum paniculatum es una hierba adventicia ampliamente distribuida en Argentina, que tiene importancia económica como maleza de cultivos resistente a herbicidas. Esta especie se presenta en el campo con dos morfotipos y ellos se distinguen por la forma, tamaño y color de sus flores, frutos y hojas. El objetivo de este trabajo fue determinar las características morfo-anatómicas (de hoja y tallo), citogenéticas y moleculares en dos morfotipos de la provincia de Tucumán (Argentina), y establecer diferencias entre ellos. Se utilizaron técnicas morfo-anatómicas y citogenéticas clásicas y se realizaron análisis moleculares con el marcador ITS2. Los resultados evidencian que las características morfológicas, anatómicas, citogenéticas y moleculares de Talinum paniculatum permitieron diferenciar los morfotipos MT1 y MT2. Se concluye que el MT1 corresponde a T. paniculatum y el MT2 a un taxón diferente que aún no se mencionó para la flora de Argentina.
ABSTRACT Talinum paniculatum is an adventitious herb widely distributed in the Argentina. This plant is considered as an economically important herbicide-resistant weed. This species shows two morphotypes in the field which are differentiated by shape, size and colour of their flowers leaves and fruits. The aims of this work were to determinate morpho-anatomical (leave and stem), cytogenetic and molecular traits of two morphotypes from Tucumán province (Argentina) and to establish differences between them. Classical morpho-anatomical and cytogenetic techniques were used, molecular analysis based on the ITS2 marker were performed. The results showed that morphological, anatomical, cytogenetic and molecular traits of T. paniculatum allow us to differentiate the MT1 and MT2 morphotypes. We concluded that MT1 match with T. paniculatum and MT2 is a different taxon still not described for the flora of Argentina.
ABSTRACT
Seed biology is a relevant aspect of tropical forests because it is central to the understanding of processes of plant establishment, succession and natural regeneration. Anadenanthera colubrina var. cebil is a timber tree from South America that produces large seeds with thin weak teguments, which is uncommon among legumes. This study describes the morphology and anatomy of the seed coat, the viability, imbibition, and germination in this species. Seeds used during the essays came from 10 trees that grow naturally in Horco Molle, province of Tucumán, Argentina. Seed morphology was described from a sample of 20 units. The seed coat surface was examined with a scanning electron microscope. Transverse sections of hydrated and non-hydrated seeds were employed to describe the histological structure of the seed coat. Hydration, viability and germination experiments were performed under laboratory controlled conditions; and the experimental design consisted of 10 replicas of 10 seeds each. Viability and germination tests were conducted using freshly fallen seeds and seeds stored for five months. Morphologically the seeds of A. colubrina var. cebil are circular to subcircular, laterally compressed, smooth, bright brown and have a horseshoe fissure line (=pleurogram) on both sides. The seed coat comprises five tissue layers and a double (external and internal) cuticle. The outer cuticle (on the epidermis) is smooth and interrupted by microcracks and pores of variable depth. The epidermis consists of macroesclereids with non-lignified secondary walls. This layer is separated from the underlying ones during seed hydration. The other layers of internal tissues are comprised of osteosclereids, parenchyma, osteosclereids, and macrosclereids. The percentage of viable seeds was 93%, decreasing to 75% in seeds with five months old. Seed mass increased 76% after the first eight hours of hydration. Germination percentage was 75% after 76 hours. Germination of seeds stored for five months decreased to 12%. The results showed that seeds of A. colubrina var. cebil are highly permeable and germinate directly without a dormant period.
El cebil, Anadenanthera colubrina var. cebil (Griseb.) Altschul, es un árbol forestal de América del Sur con grandes semillas de tegumentos delgados y débiles. Este estudio describe la morfología y anatomía de la cubierta seminal del cebil y evalúa la viabilidad, la imbibición y germinación de las semillas. Morfológicamente las semillas son circulares a subcirculares, comprimidas lateralmente, lisas, marrón lustrosas, con una línea fisural en forma de herradura en ambas caras. Histológicamente la cubierta seminal comprende cinco capas de células y una cutícula externa e interna. La cutícula externa es lisa y presenta microfisuras y poros de profundidad variable. La epidermis consiste de un estrato de macroesclereidas con paredes secundarias no lignificadas. Los siguientes tejidos internos incluyen, osteosclereidas, parénquima, osteoscleridas y macroesceleridas. El porcentaje de semillas viables fue del 93%, disminuyendo al 75% en semillas con cinco meses de almacenamiento. Las semillas incrementaron el 76% de su masa durante las primeras 8 horas de hidratación. El porcentaje de germinación en semillas nuevas fue del 75% al término de 76 horas y del 12% en semillas almacenadas por cinco meses. Los resultados confirman que las semillas de A. colubrina var. cebil son altamente permeables y germinan sin un período de reposo.