Embryogenesis and germination in rye (Secale cereale L.) : 1. Fine structure of the developing embryo

Multi-Response Optimization of the Malting Process of an Italian Landrace of Rye (Secale cereale L.) Using Response Surface Methodology and Desirability Function Coupled with Genetic Algorithm

Rye is used in some applications in the food and beverage industry and for the preparation of functional foods. It is an interesting raw material in malting and brewing due to its characteristic contribution to the beer's color, turbidity, foam and aroma. The aim of this work was to optimize the micro-malting process of a rye landrace. The response surface methodology (RSM) was applied to study the influence of three malting parameters (germination time, germination temperature and degree of steeping) on the quality traits of malted rye. Long germination times at high temperatures resulted in an increase in the extract and Kolbach index. The model for the apparent attenuation limit showed a particular pattern, whereby time and temperature inversely influenced the response. The lowest viscosities were determined in the worts produced from highly modified malts. Optimization of the variables under study was achieved by means of a desirability function and a genetic algorithm. The two methodologies provided similar results. The best combination of parameters to optimize the malting process on the rye landrace under study was achieved at 6 days, 12 °C and 44 g/100 g.

Ultrastructural changes in the endoplasmic reticulum during dormancy release of apple embryos (Pyrus malus L.)

Apple embryos were treated by cold (0°C) within the fruits, to break their dormancy; the controls were treated at 12°C or at 20°C. Ultrastructural features of meristematic cells in the embryonic axis were compared for each treatment. The organization of the cells of dormant embryos was described: Endoplasmic reticulum consisted in some short rough cisternae; lipid droplets regularly arranged near the plasmalemma constituted a kind of shell; mitochondria had a few cristae; and dictyosomes were rarely observed. All these features are typical of dry seeds. After cold treatments, the only evolution observed was in the endoplasmic reticulum, where highly organized stacks appeared progressively as a function of time at 0°C. An intermediate temperature (12°C) induced similar formations in the reticulum but they were rarely observed and their degree of organization was lower than that obtained at 0°C. At 20°C, endoplasmic reticulum resembled that of the dormant embryo cells. The relation between the appearance of these structures in the reticulum and the disappearance of dormancy induced by cold is discussed.

Sedimentation properties of preformed messenger particles in dry rye embryo extracts

Two classes of messenger containing particles can be distinguished in cell-free extracts from dry rye (Secale cereale, L.; var. Celestijner) embryos. A part of the endogenous template activity is associated with large structures, even during in vitro translation. Treatment with detergents results in a partial solubilization of the messenger particles from the large, presumably membranous structures. The sedimentation behavior of the "soluble" mRNP particles (about 75% of the total endogenous template activity) is strongly influenced by the composition of the homogenization medium. At high Mg(2+) or Ca(2+) concentrations, and at low pH, the soluble mRNP particles form aggregates sedimenting at low centrifugal forces. This peculiar behavior is of partical interest with respect to the preparation of cell-free extracts with low endogenous template activity.

Embryogenesis and germination in rye (Secale cereale L.) : III. Fine structure and biochemistry of the non-viable embryo

Fine structural investigations of non-viable rye grains indicate recognisible abnormalities in the plasmalemma and mitochondrial membranes of the unimbibed embryo. Once such grains are wetted there is rapid and progressive disorganisation of the tissue. Biochemical studies show a reduced uptake of water, lack of respiratory activity and a failure in nucleic acid and protein synthesis. Whereas total DNA, RNA and protein levels are unchanged on loss of viability, the integrity of DNA and RNA is impaired and ribosomal RNA and soluble protein levels are reduced.

Embryogenesis and germination in rye (Secale cereale L.) : II. Biochemical and fine structural changes during germination

When rye embryos imbibe water they rapidly return to a condition of biochemical and structural complexity. Three stages of imbibition can be recognised: Phase I a short period (10 min) of physical wetting; Phase II a longer period (1 h) when little further imbibition occurs, followed by Phase III a continuous phase of active water uptake. The latter coincides with an increase in respiration rate and an increase both in the number of mitochondria and of cristae within them. Changes in fine structure become evident in all organelles in Phase III, after 2 h of imbibition. In the unimbibed embryo endoplasmic reticulum is present only as short crescents associated with electron lucent bodies, but in Phase III the endoplasmic reticulum proliferates to form many surrounding cirlets. After 6 h these circlets become fewer and instead the endoplasmic reticulum is seen in close association with the nuclear membrane. Concurrently incorporation of radioactive uridine and thymidine is first detectible. This suggests that the large increase in protein synthesis occurs on new ribosomes present on the reticulum associated with the nuclear membrane. For the first 6 h protein synthesis must occur either on polysomes within the dense packing of ribosomes or on these circlets of endoplasmic reticulum associated with electron lucent bodies.