Storage reserves and cellular water in mature seeds of Araucaria angustifolia

Abstract

Seed tissues of Araucaria angustifolia (Bertol.) Kuntze were investigated using histochemistry, transmission electron microscopy (TEM) and energy dispersive X‐ray (EDX) analysis. Moisture content and water status in tissues were also evaluated. In the embryo, TEM studies revealed the presence of one to several central vacuoles and a peripheral layer of cytoplasm in cells from different tissues of the cotyledons and axis. In the cytoplasm, lipid bodies, starch grains, mitochondria and a nucleus are evident. In most tissues, vacuoles contain proteins, indicating that the storage proteins are highly hydrated. In cells of the root cap, proteins are stored in discrete protein bodies. Both protein storage vacuoles and discrete protein bodies have inclusions of crystal globoids. EDX analysis of globoids revealed the presence of P, K and Mg as the main constituents and traces of S, Ca and Fe. In the root and shoot meristems, deposits of phytoferritin are present in the stroma of proplastids. The gametophyte consists of cells characterized by relatively thin cell walls and one to several nuclei per cell. Protein and lipid bodies are present, although starch is the most conspicuous reserve. Immediately after shedding, moisture content is approximately 145% (dry weight) for the embryo and 95% (dry weight) for the gametophyte. Calorimetric studies reveal that axes and cotyledons have a very high content of freezable water, corresponding to types 5 and 4, i.e. dilute and concentrated (or capillary) solution, respectively. The results are discussed in relation to the behaviour of the species, which has been categorized as recalcitrant. © 2002 The Linnean Society of London. Botanical Journal of the Linnean Society, 2002, 140, 273−281.

Protein expression during seed development in Araucaria angustifolia: transient accumulation of class IV chitinases and arabinogalactan proteins

“…As observed in seeds of Lycopersicon esculentum (Wu et al 2001) and Cucumis melo (Witmer et al 2003), the induction of several proteins exhibiting chitinolytic activity during seed maturation is probably related to a pro-active defense strategy against pathogen attack. During seed maturation in A. angustifolia, zygotic embryos and megagametophytes accumulate water, lipids, proteins, and carbohydrates (Astarita et al 2003, Panza et al 2002 thus becoming an attractive target for microbial invasion. Furthermore, Araucaria sp.…”

“…However, in A. angustifolia, limitations have been encountered for plant regeneration through somatic embryogenesis. Seeds of A. angustifolia are recalcitrant (Panza et al 2002), and consequently, conditions often used for maturation of somatic embryos in conifers with orthodox seed type do not promote normal embryo development (Guerra et al 2000, Steiner et al in press). Unlike orthodox seeds, little is known about protein patterns during recalcitrant seed development.…”

Hypocotyl of seedlings of the large-seeded species Araucaria angustifolia: an important underground sink of the seed reserves

“…Uncontrolled logging activities in the past resulted in a dramatic reduction in the number and size of its populations, and this species is today critically endangered (Farjon 2006). In addition to its valuable wood, the species produces large (*6 g, FW), recalcitrant seeds (called ''pinhões'') with a well-developed, starchy female gametophyte Panza et al 2002). These seeds are important winter food sources for many animals, including birds and mammals, which make it a keystone species in those forest ecosystems (Pereira and Ganade 2008).…”

Comparison of seedling growth among three co-occurring varieties of Araucaria angustifolia (Bertol.) Kuntze under greenhouse conditions

“…Thus, seeds from the "angustifolia" variety were collected fi rst and stored longer, and seeds from the "caiova" and "indehiscens" varieties were collected last and stored for a shorter period of time. Considering the recalcitrant nature of the seeds (Panza et al 2002), reduction of seed viability upon storage could be expected. However, we believe that any unaccounted difference in seed size and/ or viability did not affect the signifi cance of our results: fi rst, because seedlings that grew more were the ones that came from seeds that were stored longer; and second, because if seed vigor and/or size were to play a role in seedling growth, differences in plant size would have manifested themselves early in the growing period, since the most obvious impact of seed mass is on initial seedling size (Westoby et al 2002;Kennedy et al 2004).…”