Samanea saman has rapid phytochrome-rognlated nyctinasty: red light preceding darknes.s causes pinnules to close wliile far-rod light aUows opening-Not only the initial anfjlo of the pinnules, but Ihc degree of control by phytocln-ome depends on tbe 'subjective time of day" at wbich tbe ti.ssue is exposed. Kxcised pairs of pinnule.s close rapidly when submerged in water; such closure is prevented by bubbling oxygen through the water. However, if submergence closure were due solely to low oxygen levels, tben nonsubmerged pinnules in a pure nitrogen atmosphere sbould also clo.se. Instead, they neither close nor respond to light, but they do re.sjjond when air is readmitted, indicating that oxygen is necessary for movement rather than for photoreception. The closure of .submergod piunules remains nnexplained. Attempts to detect effects of red or far-red on oxygen uptake by pulvinus tissue were unsuccessful.The following method has been used to test the effects of various inhibitors and other substances: pinnide.s are excised at tbe fir.st hour of tbe day, trimmed, submerged iu a seale
A variety of sterilizing agents were tested to develop a standard procedure for surface decontaminating seeds to produce axenic seedlings. The use of calcium hypochlorite (0.5% phosphate buffer, pH 6) for 10 min followed by three sterile water rinses was among the most effective agents, and it did not injure some species as did sodium hypochlorite, formaldehyde, ethylene oxide and mercuric chloride. Some species contained internal microbes requiring severe treatments which killed or injured the seedling, while other species were “decontaminated” with a sterile water rinse. The percentage of seeds with internal microbes varied considerably among plant species, seed lot, and the length of seed storage. Thus, with seeds not easily decontaminated, screening of additional seed lots would be more profitable than testing additional decontamination agents. Release of microbes from the seed's interior is associated with germination, and microbial testing must last at least 11 days. Nutrient agar permitted growth, although the seedlings outgrew petri plates too quickly for adequate certification. These seedlings were transferred to nutrient agar in quart jars in which an internal pool of broth was periodically agitated to permit microbial sampling of the leaves while the plant grew.
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