Seed germination water uptake

Rue infusion was tested for its allelopathic activity in vitro on water uptake and germination of radish seeds. Seeds of radish (Raphanus sativus L.) Saxa, collected during 2003, were purchased from Improta Co., Naples. 

Manz, B., Muller, K, Kucera, B., Volke, F. Leubner-Metzger, G. (2005). Water Uptake and Distribution in Germinating Tobacco Seeds Investigated in Vivo by Nuclear Magnetic Resonance Imaging. Plant Physiology, Vol. 138, No. 3 0uly 2005), pp. 1538-1551, ISSN 1532-2548... 

Many seeds placed in distilled water in Petri dishes under optimum conditions for germination show a triphasic pattern of water uptake as shown in Figure 4.6. Initial uptake of water in Phase I (i.e. imbibition) is a consequence of the matric forces (i/cell walls and cell contents of the seed, and this uptake occurs irrespective of whether a seed is dormant or non-dormant, viable or non-viable. Phase II is the lag period of water uptake, when the matric potential is high (less negative), as is the solute or osmotic potential Dead and dormant seeds maintain this level of hydration typical of Phase II, but unlike germinating seeds they do not enter Phase III, which is associated with visible germination. 

Fig. 4.6. Triphasic pattern of water uptake by germinating seeds...

Fig. 5.4A and B. Time course of increases in (A) water uptake, oxygen consumption and germination and in (B) total adenine nucleotides, ADP and ATP in lettuce seeds. Symbols... 

Examples of Epicotyl and Hypocotyl Dormancy. It is particularly well-known of our Rosaceae that their seeds require vernalization. In the case of the apple it has been found (Fig. 203) that if the seed coat is removed germination still does not take place. If, however, the thin endosperm pellicle is also removed, the embryos germinate. (We have already mentioned that the endosperm of the Rosaceae is impermeable to gases and that, for example, hydrogen cyanide formed after water uptake cannot escape.) The seedlings of other Rosaceae as well as the apple show. 

I. Stereomicroscopy of radish seeds The studies were carried out after 18 h in the presence and absence of rue extract, when most of the seeds soaked in water were germinating. Treated seeds were dormant, and the different uptake of water into these seeds was evident. 

A developing embryo produces ABA, which incepts and maintains mature seed dormancy. Germination begins with the uptake of water by imbibition of the dry seed and is followed by embryo expansion. Usually, it is considered complete when the radicle is through all the covering layers. There is still controversy whether... 

Seed and fruit coats can act as barriers to the uptake of water and thus prevent or retard germination. They can also affect respiration by limiting the permeability to oxygen. Coat effects on germination and the restriction of gaseous exchange is another topic reserved for the second volume. 

To illustrate the activation of metabolism which follows the uptake of water by the air-dry seed we quoted rates of respiration and expressed these in terms of oxygen absorption per unit of time. For most seeds oxygen is as essential as water for germination because... 

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