Haberlandt’s Dogmatic Dream and Its First Realisation

As vividly described in the review by Vasil (2008), the alleged friendship between the botanist Matthias Jakob Schleiden (1804–1881) and the animal physiologist Theodor Schwann (1810–1882) stimulated, among others, the formation of the “cell theory”. Schleiden (1838) was the first to formulate the hypothesis that all plant or animal structures are composed of cells (or their derivatives) that preserve the complete functional potential of the organism.

Cell Biology in Plant Propagation and Breeding

Self-repair of individual somatic cells is an almost universal property of multicellular organisms, both plants and animals. This ability is necessary to allow continuous replacement of cells lost through senescence or damaged by wounding. In both lower animals and most plants, the regeneration process can lead to the formation of new organs. In plants particularly, various regeneration strategies have culminated in mechanisms of vegetative propagation that either complement or even entirely substitute sexual propagation.

From Neˇmec and Haberlandt to Plant Molecular Biology

The high regenerative capacity of plants is a crucial feature of their life strategy. It is an essential part of the mechanisms that both allow these sessile organisms to repair injury caused by pathogens, herbivores and abiotic factors and to undergo rapid vegetative reproduction, so allowing them to dominate in particular environmental niches. Furthermore, various forms of natural regeneration contribute to techniques that are widely used in plant propagation and plant breeding. The biological nature of plant regeneration has been studied since the very beginnings of plant physiology as a science. Research on regeneration of intact plants in vivo was conducted by Bohumil Ne ˇmec, and early studies of in vitro regeneration in plant tissue cultures were carried out by Gottlieb Haberlandt. At this stage, however, suggestions that somatic plant cells possessed a regeneration “totipotency” were in practice often not acknowledged. Nevertheless, real experiments demonstrated that the regenerative ability of particular cells and tissues is clearly determined by the specific interplay of both genetic (or epigenetic) and physiological factors. This makes some systems “nonresponsive” to the standard regeneration procedures.

This regenerative recalcitrancy hampers both the routine vegetative propagation of various plant species and the construction of genetically modified crops. This chapter addresses the basic historical background of studies on plant regeneration and discusses both the results and ideas acquired by means of classical anatomical and morphological studies in the light of our current state of information obtained using modern molecular techniques. The present knowledge of plant regeneration is also viewed in the light of studies of structure and function of the “stem cell niches” of multicellular organisms, examining their role in the ontogenesis of intact plants and in the processes of embryogenesis and organogenesis in vitro. With reference to other chapters in this book, the role of genetics for the realisation of these processes as well as the role of various regulatory factors, of both exogenous and endogenous nature – especially phytohormones – is also examined. The importance to classify regenerative processes unambiguously using exact terminology (in the context of the allied field of regenerative medicine) as a prerequisite for the formation and validation of appropriate working hypotheses is discussed. Finally, this chapter summarises the main problems of current research on regenerative processes in plants and outlines possible directions for solving problems of recalcitrant materials in the context of their use for application.

Insertional Mutagenesis Using T-DNA Tagging

A soil bacterium, Agrobacterium, transfers the T-DNA containing genes that encode the proteins involved in biosynthesis of plant growth factors and bacterial nutrients. Because none of the genes carried by the T-DNA are required for the transfer, foreign DNA can be inserted into the plant chromosome by putting the sequences between two T-DNA borders and using the Agrobacterium transfer system. Utilising this naturally occurring property, efficient transformation protocols have been developed for Arabidopsis (Bechtold et al., 1993) and rice (Hiei et al., 1994). It is now feasible to rapidly generate the thousands of transformants necessary for investigating genome-wide mutagenesis (Clogh and Bent 1998; Jeon et al., 2000).

Novel Approaches for Understanding Germination Control

QTL Analyses

Dormancy is a quantitative trait, involving many genes and is influenced substantially by environmental factors. Within a given plant species, different accessions of wild plants and different varieties of cultivated plants exhibit genetic variation in seed dormancy. Quantitative traits are becoming more amenable to genetic analysis because the position of quantitative trait loci (QTL) and the relative contribution of these loci can now be determined (reviewed in Koornneef et al., 2002). 

Role of Gibberellins in Dormancy and Germination

A hormone balance theory has been invoked in which ABA and GA act antagonistically to control both dormancy breakage and germination (Karssen and Lacka, 1986; Karssen, 1995 and references therein). Generally GAs are viewed as important for the promotion and maintenance of germination, while ABA controls seed developmental events including the inception of dormancy (Bewley, 1997). However, GA also appears to act as an antagonistic to ABA function during seed development (White et al., 2000). 

Role of ABA and Components of the ABA Signalling Pathway

(1) Promotion of Developmental Processes, Prevention of Precocious Germination and Induction of Dormancy During Seed Development

Whether a seed is dormant or quiescent at maturity, its quality and vigour rely heavily on processes that occurred during seed development: reserve deposition (accumulation of storage proteins and storage lipids or starch), regulation of precocious germination, and development of stress tolerance. Control of seed maturation in turn is mediated by key interactions between different hormone signalling pathways and other regulatory cues provided by the seed environment.

Camellia sinensis: The Plant Behind a Cup of Tea

Camellia sinensis is a shrub native to East, South and Southeast Asia. It is now cultivated across the world in tropical and sub-tropical regions. In 2012 over 4.8 million tonnes of tea was produced (1). The plants are harvested by hand every few weeks with only the bud and first 2-3 leaves removed.

Soybean (Glyine Max) a Globally Important Crop Plant That Originates From Asia

The seeds (called soybeans) are rich in protein (40% of dry weight) and contain a good mix of essential amino acids needed by humans (1). Not surprisingly, this makes soybeans and their products popular with vegetarians and vegans as a source of non-animal protein. However, soybean-protein is also widely used as the main protein source for intensive farming of animals including chickens, cows and pigs.