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- Author or Editor: R. A. Backhaus x
Morphactin applied to stems of guayule (Parthenium argentatum Gray) at rates of 1000 and 5000 ppm caused significant increases in stem diameter over non-treated controls after 120 days. However, rubber content remained unchanged. Additional treatment with DCPTA did not stimulate rubber accumulation in the morphactin-treated plants. Morphactin treatments also caused a decrease in plant dry weight. Morphactin and DCPTA in combination appeared to have a negative, synergistic effect on plant growth. Lack of rubber accumulation in morphactin-treated plants was attributed to disorganized, convoluted, vascular cells within the cortical tissue, which is the primary site of rubber accumulation. Chemical names used: methyl-2-chloro-9-hydroxy-fluorene-9-carboxylate (morphactin); 2-(3,4-dichlorophenoxy)-triethylamine (DCPTA).
Flowering response in guayule (Parthenium argentatum Gray) was found to be photoperiodically induced by long days. The critical daylength for flowering was between 9.5 and 11 hours. The flowering response was the same when measured as days to first flower, node to first flower, or percentage of plants flowering. Plants flowered within 57 days of emergence under 16-hour long days or 8-hour short days, with a light interruption midway through the dark period, but did not flower under 8-hour short days. Flowering was most rapid under 20-hour days and slowed as day-lengths approached 11 hours. Flower induction occurred with exposure to as few as three 20-hour photocycles.
Morphactins, mixed with non-phytotoxic paraffinic, low molecular weight oil, were applied as bark bands and tested for growth inhibition of trees growing under field conditions. Three species were tested: Monterey pine (Pinus radiata D. Don.), olive (Olea europaea L. cv. Manzanillo) and eucalyptus (Eucalyptus globulus Labill). Shoot elongation was inhibited in all three species, but sensitivity to the treatment varied.
Etridiazole, etridiazole/thiophanate, fenaminosulf, Captan, and pentachloronitrobenzene (PCNB) were tested for prevention of damping-off of guayule (Parthenium argentatum Gray) seedlings in greenhouse tests. Fungicides were incorporated into a magnesium silicate fluid drilling gel containing pregerminated seeds. The seeds were sown into vermiculite and inoculated with Pythium debaryanum or Rhizoctonia solani. Phytotoxic levels of the fungicides were determined. PCNB was very effective in controlling damping-off caused by R. solani. Captan and fenaminosulf provided over 50% protection from damping-off caused by P. debaryanum. Etridiazole and etridiazole/thiophanate controlled preemergence damping-off, but did not control postemergence damping-off caused by P. debaryanum. Chemical name used: 3a,4,7,7atetrahydro-2-[(trichloromethyl)thiol]-1H-isoindole-1,3(2H)-dione (Captan).