Germination of Kalanchoé blossfeldiana seeds is absolutely light‐requiring and needs repeated daily light periods. With increasing length of the photoperiod there was a gradual escape from the far‐red inhibition. This escape depended also upon the duration of the far‐red exposure: 10‐second far‐red caused a strong inhibition after a 10‐ to 30‐minute photoperiod and did not inhibit after a 4‐hour day, although the effect of the latter was completely suppressed by 5 minutes far‐red. The action of a 12‐hour photoperiod was not reversed by 10 minutes far‐red but it was by 12 hours far‐red. Light intensity and temperature during the photoperiod were two other important factors influencing the escape from far‐red inhibition. The common features of this escape displayed in very different photomorphological responses are stressed. In order to explain our results in terms of phytochrome action, we distinguish two effects of white light: 1) on the initial photoconversion of the inactive to the active PFR form 2) on the much slower transformation of PFR to a reacted form P*FR; the latter reaction can also proceed in darkness, but is enhanced by light and is dependent upon light intensity and temperature; this reacted phytochrome is not reversible by a brief far‐red illumination.

The effects of irradiations with different proportions of red/farred light and of gibberellic acid on the phytochrome‐mediated seed germination of Kalanchoë blossfeldiana cv. Feuerblüte, were studied.The seed coat transmits much more red than far‐red light, and therefore the energy ratio between 660 nm and 730 nm is given only for the transmitted light. Decreasing this ratio from 65 to 1.0 caused only a very slight inhibition. If this ratio is further lowered to 0.64, a 10 min terminal irradiation after a 3‐h white light photoperiod is inhibitory, but a 12‐h photoperiod or continuous irradiation is not. If the ratio is decreased to 0.44 or 0.31, a 12‐h photoperiod is now also inhibitory, although continuous irradiation and 10 min terminal irradiation are still more inhibitory. These results are discussed in terms of phytochrome phototransformations.Although gibberellic acid is unable to cause any germination in complete darkness, it can result in a very high germination percentage, if combined with treatments which by themselves do not induce any germination such as continuous far‐red, terminal far‐red after short photoperiods, or very short photoperiods at 25°C. These results point to a strong synergism between gibberellic acid and the so‐called stabilized form of phytochrome, P*FR.

Moringa oleifera, Lam., commonly named horseradish or drumstick tree, is cultivated for multiple purposes because all its parts including seeds, stems, shoots, leaves, flowers, fruits and roots are useful. The objective of this study was to evaluate salt tolerance of Moringa oleifera during its early growth stage. A pot experiment was conducted in the greenhouse during two successive seasons 2005/2006 and 2006/2007; at the Nubaria Research and Production Station. Equal amounts of sodium chloride and calcium chloride (w: w, 1:1) were mixed with sandy loam soil at six rates: 0.0, 0.2, 0.4, 0.6, 0.8 and 1.0 %.Forty -day -old seedlings were planted and kept to grow for 18 months until recording the data. Young Moringa trees were affected by soil salinity at relatively high levels. Low salt concentrations slightly reduced growth, whereas increasing salinity decreased plant height, stem diameter, branch number, leaf number, and root length. High salinity had a detrimental effect on shoot and root dry weights, and pigment contents. Nitrogen, phosphorous, and potassium contents in all plant parts were greatly reduced under high salinity levels. Sodium content increased with increasing salinity and showed a higher accumulation in roots.

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