Stem collapse

The pathogens (103 to 104 spores mL 1) caused significant shoot growth inhibition within 25 to 30 h and seedling death within 40 to 50 h. Stem collapse time, as a function of various spore concentrations, was also a useful bioassay parameter. Nonlinear regression analysis86 was used to model stem collapse time as a function of spore concentration (Fig. 16.2, solid lines). The trend used for this model was an exponential decay model of the form ... 

Effects of different C. truncatum and A. cassiae spore concentrations on seedling stem collapse bioassay of hemp sesbania and sicklepod, respectively. Solid lines for each data set = predicted trends for C. truncatum/hemp sesbania and for A. cass/ ae/sicklepod interactions, respectively, based on the exponential decay model described in the text. Triangles = recorded values and closed circles = recorded values for A. cass/ ae/sicklepod and C. truncatum/hemp sesbania, respectively. (From Hoagland, R. E. 1995, Biocontrol Sci. Techno ., 5, 251-259. With permission.)... 

Leaves wilt stems collapse. Cause Borers. Both European corn borer and stalk borer caterpillars are long, thin, and striped and tunnel within dahlia stems and flower stalks, causing collapse. Inspection of damaged plants reveals small, round holes in stems. Remove and destroy infested stems clean up debris where pests overwinter. If borers have been a problem in past years, spray BTK weekly in early summer before borers enter stems. 

After treatment characteristic phytotoxic symptoms are developed by plants sensitive to urea herbicides. Acute symptoms are manifested by the withering of leaf tips and leaf edges, chlorosis and water-soaked blotches. Subsequently, chronic symptoms, such as increased chlorosis, wilting, plant-growth reduction, defoliation, and stem collapse are seen. The process ends in the complete decay of the plant (Bucha and Todd, 1951 Minshall, 1954, 1957). 

Brown rot in the stem pith followed by stem collapse. 

Symptoms Stems become dark brown at soil level. Gray mold develops on young buds and flowers. Stems wilt and collapse. Flowers may fail to open. 

The second step of the proposed chain of events, resistance as a direct consequence of cell death, is still controversial (82-86). In the wheat-stem rust system, evidence favouring the idea of hypersensitive cell death as the cause of resistance (30,31,87-90) contrasts to results suggesting cell collapse as being a mere consequence of a yet unknown preceding resistance mechanism (90-97). 

Macri R, Vianello A, Pennazio S. 1986. Salicylate-collapsed membrane potential in pea stem mitochondria. Physiol Plantarum 67 136-140. 

Fig. 10.4. Overall diagram of the operational zone of the time of the test (not to scale). At the bottom of the shaft, the container is surrounded by basalt sand. Above, the shaft is filled with cement and aggregates up to the top of the future collapse zone. The top of this zone corresponds to the base of the effective part of the stemming column. The container is linked by a cable harness to the recording barge, which transmits the...

Single unstained protein complexes must be prepared by freeze-drying to prevent structural collapse during dehydration [10]. STEM dark-field images... 

Stems blacken at base leaves yellow and wilt plant collapses. Cause Crown rot. Hostas are susceptible to fungal and bacterial attack when grown in poorly drained soil. Crown... 

Brown to gray spots on leaves and stems, and dark, gummy stems are caused by gummy stem blight. Infected leaves turn yellow and die. Disease begins as spots on stems, which become streaks stems then turn dark and gummy. When it attacks fruit, the disease is called black rot Infected fruit has round, black spots and the fruit flesh collapses. For an illustration of this disease, see page 148. 

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