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  • Author or Editor: Robert L. Houtz x
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Plants of Main Dwarf, a short-internode mutant of the normal-internode `Mainstream' muskmelon (Cucumis melo L.), have shorter internodes, fewer nodes, less total vine length, less total dry weight, smaller leaves, increased chlorophyll concentrations, increased specific leaf dry weight, and increased ribulose-1, 5-bisphosphate carboxylase/oxygenase (EC 4.1.1.39, rubisco) activity per unit leaf area than `Mainstream' plants. Main Dwarf plants produce an equal number of fruit as `Mainstream' plants but are only half their size. Many of the plant and fruit characteristics for F1(Main Dwarf × `Mainstream') are similar to those of `Mainstream', except for greater leaf chlorophyll and rubisco activity per unit leaf area. The F1 (`Mainstream' × Main Dwarf) produced fewer and lower weight fruit than its reciprocal, F1 (Main Dwarf × `Mainstream').

Free access

Abstract

Paclobutrazol and flurprimidol were foliar-applied to drip at 250 mg·liter–1 to ribbon-row grown ‘Honeoye’ strawberry plants 1 month after planting. Compared to untreated plants, paclobutrazol treatment increased leaf chlorophyll per unit area, but had no effect on leaf total protein or dry weight per unit area of leaf disks sampled 3 and 12 months after treatment. Flurprimidol had no effect on these leaf characteristics. Net photosynthetic rates were reduced 3 months after application of both inhibitors, but were slightly increased in paclobutrazol-treated plants only in the fruit harvest period 12 months after application. Ribulose-1,5-bisphosphate carboxylase/oxygenase (rubisco) activities were significantly reduced in inhibitor-treated leaves 3 months after application, whereas 12 months later, rubisco activity averaged 34% less than that from control leaves, but was not statistically significant at the 5% level. Leaf conductance was significantly increased by paclobutrazol treatment when measured 12 months after application. Chemical names used: β-[(4-chlorphenyl)methyl]-α-(1,1-dimethylethyl)-1H-1,2,4-triazole-1-ethanol (paclobutrazol); α-(1-methylethyl)α-[4-(trifluoromethoxy)phenyl]-5-pyrimidinemethanol (flurprimidol).

Open Access

Abstract

Sap collected from trees of sugar maple (Acer saccharum Marsh.) in the springs of 1978, 1980, and 1981 was analyzed for 1-triacontanol (TRIA) content. TRIA was present at physiologically active concentrations which varied quadratically with sampling time during each spring season. The maximum TRIA concentration observed was about 11.4 × 10-9M. The highest concentration of TRIA in the sap shifted each year of collection.

Open Access

A technique was developed for controlled micro-release of CO2 into the leaf canopy of strawberry and tomato plants under field production conditions; The leaf canopy atmosphere of tomato plants was enriched to 500 and 1200 ppm CO2 with release rates of 60 and 300 l/h·30 m of row respectively. After 60 days of enrichment for 6 h each day beginning at fruit set, the total shoot biomass and yield was increased 41% and 25 % respectively for the high CO2 release rate. Strawberry leaf canopies did not show increased CO levels with CO2 enrichment except under ventilated2 row-covers where the atmospheric CO2 level was increased to 1500 ppm CO2. Although the total biomass was increased 39% this did not translate into increased yields perhaps due to excessive temperatures under the row covers.

Free access

Abstract

The yield response of crops to triacontanol (TRIA) applied as a colloidal dispersion was tested with 13 crop species in 45 field experiments over a 3-year period. Foliar application of TRIA resulted in treatment effects with 11 of the 13 crops and in 30 of the 45 experiments. The average yield increase was 14% with the optimum TRIA concentration in tests where yield was significantly increased, and was 5% over all 45 experiments. In seven experiments, significant yield decreases averaging 10% were measured with TRIA concentrations that increased crop yield of the same species in other tests. The most effective TRIA concentrations generally were 0.1 to 1.0 μg·liter−1. No particular stage of crop development for treatment was optimal for all crops. Based on the results of these studies, TRIA cannot be recommended for commercial application to crops in Michigan or similar environments. Chemical names used: 1-triacontanol (triacontanol).

Open Access