ABSTRACT
Escobedia grandiflora(L.f.) Kuntze is a wild hemiparasitic plant with orange roots. Little is known about the development of initial parasitism with the host, despite the significant value of roots for Central and South American communities. Therefore, this study aimed to characterize post-seminal structure and development of E. grandiflorain Pennisetum purpureumhost. To analyze the structure and development of E. grandiflora, seedlings, stems and roots samples were processed and examined underlight, confocal and scanning electron microscopy. Escobedia grandifloraseeds are composed of seed coat, perisperm, and embryo. Emergence of the radicle began eleven days after imbibition. Seedlings showed a root hair collar encircling the axis at the root-hypocotyl junction with elongation of internal cortical cells. Seedlings formed haustoria and successfully reached of the host roots 22 days following root emergence. In the root many starch grains were observed, albeit more scarce in the hypocotyl. After 43 days of root emergence, the seedling stage was finished with the formation of the definitive leaves, and star of the plant stage. After 64 days, root ramification, amount of starch, and orange pigmentation increased with formation of haustoria. The developmental pattern of E. grandiflora plants was slow, but the roots grew faster than the stem. Escobedia grandifloraseeds were not endospermic and have limited nutritional value. After root emergence, the young seedling must develop roots and starch storage towards to haustorium formation and attachment to host roots.
Subject(s)
Semen Analysis , Orobanchaceae/parasitology , Plant Roots , SeedsABSTRACT
The pattern of genetic variation among populations of two Orobanche gracilis Sm. taxa (var. gracilis and var. deludens (Beck) A. Pujadas) from Northern and Southern Spain growing on different hosts was analysed using RAPD markers. The diversity analysis within populations revealed a higher level of diversity in the populations from the North when compared to the Southern ones. The results of principal co-ordinate analysis (PCoA) based on Dice distances among samples clearly established the separation of samples according to the taxonomical variety and the geographical origin of each population. The Southern populations of both var. gracilis and var. deludens were more differentiated among them than those of var. gracilis from the North. The analysis of molecular variance (AMOVA) indicated that the lowest level of population differentiation was found in O. gracilis var. gracilis from the North, whereas in the case of O. gracilis var. deludens from the South most of the genetic diversity was attributable to differences among populations. Possible explanations for the distribution of variation in these populations are discussed.