Zeitschrift für Pflanzenphysiologie最新文献

We have studied the toxicity of six β-lactam antibiotics to Nicotiana tabacum cv. xanthi cells and protoplasts as well as their effect on Agrobacterium tumefaciens cells containing the bla gene from pBR322 and the plasmid pPHlJl of the P incompatibility group. Relatively high doses of ampicillin, cloxacillin, cefoxitin and vancomycin can be tolerated by plant cells while allowing rapid elimination of A. tumefaciens cells. However, young cells originating from protoplasts are more sensitive to antibiotics. A combination of cefoxitin and cloxacillin allows good control of bacterial proliferation and has no adverse effect on plant protoplast division. Histidine- and leucine-requiring mutants of A. tumefaciens proliferate very slowly in the presence of dividing protoplasts whereas E. coli HB101 carrying a bla gene do not. A. rhizogenes was also found to be sensitive to cefoxitin.

Chlorophyll-preserving and degrading substances from Artemisia capillaris Thunb. were investigated using the oat leaf assay system. These substances were isolated and identified as 1-oxo-l-phenyl-2,4-hexadiyne (capillin), l-phenyl-2,4-hexadiyne (capillen) and 3-(2-butynyl)isocoumarin (capillarin) by GC-MS analysis. Capillin and capillen were effective in chlorophyllpreserving at concentrations of more than 10 or 25 μg · ml^-1 in the dark, and at 100 or 250 μg · ml^-1 the chlorophyll retention was about 80% of the initial value. However, capillen at 500 μg · ml^-1 was effective in chlorophyll-bleaching in the light. On the other hand, these compounds, at concentrations of less than 25 or 50 μg · ml^-1, stimulated the loss of chlorophyll and completely eliminated the chlorophyll-preserving effect of kinetin in the dark. Capillarin was not effective in chlorophyll-preserving at any concentrations tested in the dark, but it stimulated the loss of chlorophyll and counteracted the chlorophyll-preserving effect of kinetin in the dark. From these results it is concluded that capillin, capillen and capillarin are essentially chlorophyll-degrading substances, and that chlorophyll-preserving activities of capillin and capillen at higher concentrations in the dark are due to their nonspecific and/or toxic effects rather than the inhibition of normal senescence.

The movement of silver thiosulphate (STS) within cut carnation flowers was monitored on a time-course basis. After a ten minute STS (^110mAg) pulse, the ^110mAg moved rapidly into all the flower parts. With time, however, the ^110mAg steadily accumulated within the receptacle. Nine days after application the radioactive silver was no longer detected in the petals and ovary. Petal applied radioactive silver nitrate showed that silver can become phloem-mobile. This silver also accumulated in the receptacle.

Extension of primary roots of Zea mays (cv. LG11) was analysed by a method of upward bending. The characteristics of extension are discussed. IAA pretreatment at several concentrations, enhanced instantaneous, total, plastic and elastic deformations, with an optimal effect for the 10^-6M concentration. All types of deformations were decreased by GA3 pretreatment at several concentrations, chiefly the plastic one. No peak was observed in the response to GA3. The timescale of rheological analysis, for roots treated with IAA (10^-6M) or GA3 (5 • 10^-7 M), showed that the effect of these two hormones is rapid.

The unicellular red alga Porphyridium cruentum was investigated by electron microscopy and morphometry under exponential growth conditions, nitrate and sulphate starvation and during regeneration to exponential growth. Lipid bodies and one plastoglobule type are formed by aggregation and fusion of cellular membranes; these membranes are derived either from excessively produced smooth endoplasmic reticulum under normal growth conditions, or by a collapse of phycobilisome-depleted thylakoids under starvation conditions. Lipid bodies function as a «membrane component store» which is used for rapid membrane synthesis during regeneration. A second type of plastoglobule is formed at tubular structures, homologous to lipid bodies of higher plants. A model for the formation and degradation of lipid bodies is presented.

Early embryo systems of Zamia pumila L. were dissected from ovules and cultured in vitro. At first, growth of suspensors was observed in early embryo systems cultured in July. The flexuous development of the suspensor in vitro can be compared to its coiling way of growth in ovulo. Therefore this contorted development in situ is not due to the pressure exerted by the ovule but is a real ontogenic phase. After two months of culture, suspensor growth is stopped, embryos enlarge and two uneven protuberances identifiable as cotyledons appear. In vitro and in ovulo there is a transfer of location of growth induction.