Penetration and early colonization in basidiosporederived infection on needles of Pinus pinea L. by Cronartium flaccidum (Alb. et Schw.) Wint.

Abstract The behaviour and the morphology of the infection structures of the monokaryotic phase of Cronartium flaccidume studied on needles of Pinus pinea seedlings inoculated with the rust basidiospore. It was found that the penetration and early colonization structures of C. flaccidum in the monokaryotic phase maintained the morphological and functional significance of the typical monokaryotic ones, even if some aspects of their behaviour seemed to recall those of the dikaryon. A possible hypothesis as to the reason for the dynamics of penetration carried out on the markedly cutinized needles of pine by C. flaccidum in the monokaryotic phase is discussed. It can be concluded that in C. flaccidum in the monokaryotic phase it is the nuclear set which determines the morphology and function of the structures involved in the infection process; this is true even if the histological characteristics of the host organ which this rust species has evolved to infect in nature, condition its way of penetration

Characterization of the seed reserves in Tillandsia (Bromeliaceae) and ultrastructural aspects of their use at germination

Abstract The nature and the use of the reserves accumulated in the seed of Tillandsia, a markedly epiphyte genus, are especially important in consideration of the subsequent seedling development. As a matter of fact, the embryo radicle degenerates precociously without emerging at the germination and the sole function of the root system is that of anchoring to the substratum. The present cytochemical and ultrastructural study carried out on mature seeds has highlighted the presence of proteins and lipids, in both the endosperm and in the cotyledon, which are both well–developed; in addition, the endosperm contains starch and calcium oxalate. At germination the reserves, broken–down by enzymes, are absorbed by the cotyledon in whose epidermis ultrastructural modifications, correlated with this austorial function, appear. A part of the nutrients absorbed is initially stored in the large vacuoles, of aleuronic origin, of the cotyledon parenchyma. The result is a water uptake. It is in this manner that the wat..