The aim of this study was to evaluate the effect of water stress on the germination of Coffea arabica seeds and the growth and development of plants from these seeds. Seeds of the cultivars Bourbon Vermelho, Mundo Novo, and BA-10 were placed to germinate in the dark at 30 ºC in the presence and absence of 100 g/L of polyethylene glycol 6000. The water stress applied delayed the beginning of seed germination by seven days in relation to seeds of the control, which had achieved responses of up to 50%, but there were no differences between the treatments at the end of the experiment. Furthermore, the length of the primary root in seeds germinated under water stress was less than in the control treatment, especially for the cultivar Mundo Novo. Plants of the cultivars Bourbon Vermelho and Mundo Novo developed from seeds previously germinated under water stress exhibited reduced height and fewer leaf pairs than those from the control, whereas ‘BA-10’ responded in a similar way in both treatments. Thus, the cultivars Bourbon Vermelho and Mundo Novo were more sensitive to the water stress applied in the germination phase than ‘BA-10’.

This study evaluated the effect of different concentrations of 2-isopentenyladenine (2-iP) on the direct somatic embryogenesis capacity of the Mundo Novo cultivar of Coffea arabica. Leaf explants were cultivated with half the MS salt concentration and the addition of sucrose (20gL^-1) and 2-iP (0; 2.5; 5; 7.5 and 10µM). The 2-iP doses of 7.5 and 10µM produced the greatest responses with respect to the percentage of explants with embryogenic structures and the size of the embryogenic structures. However, the greatest production of somatic embryos occurred on the explants treated with 10µM of 2-iP, followed by 7.5µM, whereas their production was absent or reduced with 0 and 5µM, respectively.

Somatic embryogenesis contributes to coffee breeding programs. This is a process of asexual reproduction which is based on the concept of cellular totipotency. Each haploid or somatic cell of the plant tissue has the genetic information necessary to generate a complete and functional plant. The somatic embryogenesis can occur either indirectly or directly. Coffea arabica genotypes may respond to direct, indirect, or both. In this species, the indirect somatic embryogenesis is composed of two phases, the callogenesis and the embryogenesis, while the direct pathway occurs in a single phase, without the callogenesis. In Coffea, in general, the indirect pathway is induced by the auxin and cytokinin, and the direct pathway with cytokinin only. C. arabica genotypes usually respond easily to the indirect route with high production of somatic embryos. But these are inefficient by the direct route because they present low production of embryos and the process occurs for a long time. In this review, emphasis will be given to different events that are part of the somatic embryogenesis of C. arabica occurring indirectly and in the direct pathway as well as factors that may affect its control.

Kohleria eriantha has rhizomes which are underground stems with buds enclosed by modified leaves, that store starch. The buds of this rhizome can develop in two morphological patterns: an aerial shoot (similar to the mother plant) or a rhizome, depending on the water level present in the substrate. Development of the shoot was inhibited by low water availability (1 mL) in the substrate. It was verified that ethylene and ABA were involved in controlling the development of the rhizome pattern under low water availability. Treatments with ethrel, PEG and ABA induced shoot development whereas treatments with AgNO3 or AVG inhibited shoot development. Increased ethylene and ABA were observed under conditions that inhibited shoot development. Moreover, it is suggested that ABA may induce the production of ethylene in the sections of the rhizome under low water availability.