Vegetative anatomy of <em>Lophophytum mirabile</em> subsp. <em>bolivianum</em> (Balanophoraceae) and the effect of its parasitism in the anatomy of the roots of its host <em>Anadenanthera colubrina</em> var. <em>cebil</em>

Abstract

(Balanophoraceae) y efecto de su parasitismo en la anatomía de las raíces de su hospedante Anadenanthera colubrina var. cebil. Anales Jard. Bot. Madrid 73(2): e039.El objetivo de este trabajo fue estudiar la estructura del cuerpo vegetativo de Lophophytum mirabile subsp. bolivianum (Wedd.) B. Hansen, analizar en qué grado se modifican las raíces de Anadenanthera colubrina var. cebil (Griseb.) Altschul cuando son infectadas y determinar los cambios anatómi-cos producidos por este parasitismo. Las plantas de L. mirabile subsp. bolivianum tienen un cuerpo vegetativo subterráneo o túber de forma esferoidal ahusada, que externamente es de un color castaño oscuro a negro y superficie verrugosa; carece de epidermis, estomas o tricomas. La matriz central del túber está compuesta por parénquima de reserva y abundantes haces colaterales dispersos. Las células del parásito ubicadas a nivel del cámbium de la raíz inician la formación de túberes, que surgen como exófitos del cuerpo del hospedante. En el leño de la raíz de A. colubrina var. cebil infectado por el parásito se pierde la identidad del sistema radial y axial del crecimiento secundario. Esto lleva a la formación de bucles de xilema que afectan el transporte y el desarrollo de la raíz, que detiene su crecimiento en longitud y desarrolla una agalla leñosa. La infección de L. mirabile subsp. bolivianum es causa de profundos cambios anatómicos en el desarrollo de la madera de A. colubrina var. cebil que favorecen el éxito del parásito.Palabras clave: agallas, anatomía, leño, parasitismo, raíz. Hansen, to analyze the change on roots of Anadenanthera colubrina var. cebil (Griseb.) Altschul when they are infected by this parasitic plant, and to identify the anatomical changes produced by that parasitism. L. mirabile subsp. bolivianum plants are formed by a spheroidalnarrower underground vegetative body or tuber, that externally has a dark warty surface;epidermis, stomata or trichomes are lacking. The central matrix of tuber consists of reserving parenchyma and vascular bundles. Parasitic cells located at the level of root cambium initiate the tuber formation. On the infected root of A. colubrina var. cebil, the identity of radial and axial growth of the secondary system are lost. This leads to the formation of xylem loops that affect the xylem transport and root development, which stops length growth and develops a woody gall. Infection of L. mirabile subsp. bolivianum causes profound anatomical changes in timber developing of A. colubrina var. cebil, which favor the parasite success.

Horizontal gene transfers dominate the functional mitochondrial gene space of a holoparasitic plant

“…These results are to be expected for a relatively complete transcriptome of a holoparasitic plant, in which most genes involved in photosynthesis‐related functions were probably lost. Furthermore, the vegetative form of Lophophytum is a highly derived underground tuber that lacks leaves, stomata, epidermis, and trichomes (Gonzalez & Sato, 2016); therefore, many genes related to these structures were probably lost too.…”

“…A striking example of this in parasitic plant mitochondria is the loss of respiratory complex I and its associated nine mitochondrial genes in Viscum mistletoes (Skippington et al ., 2015; Skippington et al ., 2017), with this loss leading to a highly remodeled respiratory chain and greatly diminished oxidative phosphorylation (OXPHOS; Maclean et al ., 2018; Senkler et al ., 2018). Compared with hemiparasitic, photosynthetic Viscum , holoparasite Lophophytum is substantially reduced in morphological and biochemical complexity, lacking photosynthesis, leaves, stomata, epidermis, and trichomes (Gonzalez & Sato, 2016). It would not be surprising, therefore, if Lophophytum has also lost normally essential mitochondrial functions and genes.…”