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- Author or Editor: B. Schaffer x
The effect of wind stress on growth, net CO2 assimilation (A), and leaf water potential of eighteen-month-old, containerized carambola (Averrhoa carambola cv. Arkin) and seedling sugar apple (Annona squamosa) trees was investigated. In a glasshouse, trees were exposed to fan-generated wind speeds of 0 (control), 4 (low wind; LW), or 7 (high wind; HW) m sec-1 for 4 hr/day (1000-1400 hr) for 30 days. No differences in A, stomatal conductance, transpiration, and fresh and dry wt of mature carambola or sugar apple leaves or shoots were observed among treatments. In contrast, as wind speed increased, fresh wt of immature carambola leaves and shoots decreased. For carambola and sugar apple, no significant relationship was found between mid-day leaf water potentials and wind speed. However, after 30 days, leaf water potential of carambola subjected to HW (-1.2 MPa) was lower than those of LW (-1.1 MPa) and control (-1.1 MPa) trees. For sugar apple, leaf water potential of control trees was generally higher than those of trees in the LW and HW treatments. The data indicate that exposure to wind speeds of 4 or 7 m sec-1 for as little as 4 hr/day for 30 days reduces new leaf and shoot growth of carambola trees.
Banana (Musa sp.), mango (Mangifera indica), and avocado (Persea americana) plants were grown in controlled-environment glasshouses in ambient (350 μmol CO2/mol) and enriched (700–1000 (mol CO2/mol) atmospheric CO2 concentrations. At each CO2 concentration, plants were either exposed to sink-limiting (root restriction) or non-sink-limiting conditions (no root restriction). Total carbon assimilation and dry matter accumulation were generally greater for plants in the enriched CO2 environment than for plants grown in ambient CO2. However, plants grown in the enriched CO2 environment were less efficient at assimilating carbon than plants grown in ambient CO2. There was a downward regulation of net CO2 assimilation due to root restriction that resulted in less dry matter accumulation than in non-root-restricted plants. This may explain the lower net CO2 assimilation rates often observed for tropical fruit trees grown in containers compared to those of field-grown trees. Atmospheric CO2 enrichment generally did not compensate for reductions in net CO2 assimilation and dry matter accumulation that resulted from root restriction.
The effects of amending soil with municipal soil waste (MSW) on growth, yield and heavy metal content of tomato were tested with different irrigation rates. The following MSW materials were incorporated into oolitic limestone soil: 1) Agrisoil compost (composted trash), 2) Daorganite compost (sewage sludge), 3) Eweson (composted trash and sewage sludge), and 4) no MSW (control). Two rates (high and low) were applied to the soil for each compost. There were no significant effects of irrigation rate on any of the variables tested for tomato in 1991 or 1992. Therefore, the lowest irrigation rate appeared to be adequate for optimum tomato production. Plants grown in Daorganite at the lowest rate of 8 t/ha had greater growth and yield than plants grown in the other MSW materials or the control. Agrisoil and Eweson composts did not increase growth or yield, which may have been due to suboptimal application rates of these materials. There were no differences in the concentration of heavy metals in fruit or leaves among MSW materials or rates. MSW rate generally had no effect on root heavy metal concentration, except for Eweson where the high rate resulted in a higher root zinc concentration than the low rate. There were signifant differences in root concentrations of lead, zinc, and copper among MSW materials. Leaf concentrations of all heavy metals tested were within normal ranges for tomato.
The effects of amending soil with processed municipal waste (PMW), and the interaction of PMW with trenching, irrigation rates, and fertilizer rates on growth, and yield of tomato plants were tested. In a series of experiments, two rates of each of the following PMWs were incorporated into calcareous limestone soil: 1) Agrisoil (processed trash), 2) Daorganite (processed sewage sludge), 3) Eweson compost (processed trash and sludge), and 4) no PMW (control). In some experiments, secondary applications of PMW were applied to the beds at either a high rate, a low rate or not applied (control). There was no effect of secondary PMW applications on growth or yield. Generally, plants grown on trenched plots had greater growth and yield than plants on non-trenched plots. Plants grown in Daorganite had greater growth and yield than plants grown in the other PMWs. Plants in Daorganite tended to have higher photosynthelic and transpiration rates than plants in the other treatments. For all treatments, plants grown at one-half the standard fertilizer rate had less growth than plants receiving higher fertilizer rates. There was no interaction between irrigation rate and PMW for photosynthesis, growth, or yield. Plants grown in Daorganite had the greatest growth and tended to have greater yields, regardless of the fertilizer or irrigation rate. Processed trash composts (Agrisoil and Eweson) did not increase growth and yield, which may have been due to suboptimal application rates of these materials. Further studies are underway incorporating higher rates of these materials into the soil.
The effects of municipal solid waste (MSW) materials on growth, yield, and mineral element concentrations in tomato (Lycopersicon esculentum Mill.) (1991 and 1992) and squash (Cucurbita maxima Duch. Ex Lam.) (1992 and 1993) were evaluated. Agrisoil compost (composted trash), Eweson compost (co-composted trash and sewage sludge), or Daorganite sludge (chemically and heat-treated sewage sludge) were incorporated into calcareous limestone soil of southern Florida. The control had no MSW material added to the soil. The effect of MSW on crop growth, yield, and mineral element concentrations varied considerably between years for tomato and squash. In 1991, tomato plants grown in soil amended with Eweson or Daorganite had a greater canopy volume than plants in the control treatment. Tomato plants grown in Daorganite had greater total fruit weight (1991) than plants in Agrisoil and more marketable fruit (1992) than control plants. In both years, tomato plants in Agrisoil had higher root Zn concentrations than plants in the other treatments. In 1992, tomato plants in Eweson had lower root Mn concentrations than plants in the other treatments, whereas Mg concentrations in the roots were higher in the Daorganite treatment than in Eweson. Tomato plants in Agrisoil had higher Pb concentrations in the roots than plants in all other treatments. In 1991, leaves of tomato plants in Agrisoil had lower Ca concentrations than leaves of plants in the control treatment. In 1992, leaf Zn concentrations were greater for tomato and squash in Agrisoil than in the control or Daorganite. In 1992, canopy volume and yield of squash were greater for plants in Daorganite than for plants in the control and other MSW treatments. Although canopy volume and total squash fruit weight did not differ among treatments in 1993, plant height was greater for squash plants in the MSW treatments than for those in the control. In 1993, leaf Mg concentrations were greater for squash grown in Daorganite than for plants in the control or Agrisoil. In 1993, fruit Cd concentration was higher for plants with Eweson than for plants in the control or Agrisoil. However, the fruit Cd concentration in squash grown in Eweson compost (1.0 mg/kg dry weight) was far below a hazardous level for human consumption. Our results indicate that amending calcareous soils with MSW materials can increase growth and yield of tomato and squash with negligible increases in heavy metal concentrations in fruit.
On a whole-plant basis, deblossomed ‘Tribute’ strawberry plants had higher rates of net photosynthesis (Pn) and greater leaf area than fruiting plants during the last 3 weeks of a 6-week fruiting cycle. Leaves of both fruiting and deblossomed plants had a greater dry weight and total nonstructural carbohydrate (TNSC) content than the roots, crown, or fruit. At the end of the fruiting cycle, dry weight and TNSC content of leaves were higher for deblossomed plants than fruiting plants. There was no difference in crown or root dry weights between treatments. Pn was highly correlated with plant dry weight and TNSC during the 3rd, 5th, and 6th weeks of the fruiting cycle.
In an initial experiment, ‘Tribute’ (day-neutral) and ‘Allstar’ (June bearing) strawberry [Fragaria × ananassa (Duch.)] plants were grouped into fruiting, partially deblossomed, and deblossomed treatments. Net photosynthesis (Pn), dark respiration (Rd), and stomatal conductance for CO2 (gs) were measured at 14-day intervals during the 1st fruiting cycle of both cultivars and at 7-day intervals during the 2nd fruiting cycle of ‘Tribute’. Pn of recently expanded leaves of fruiting plants was greater than that of deblossomed plants only during the 2nd week of the first fruiting cycle and the 2nd and 3rd weeks of the 2nd fruiting cycle. There were no differences in Rd or gs among treatments. At the end of the fruiting cycles, leaves, crowns, and roots of deblossomed plants of both cultivars had greater dry weights than those of fruiting plants. At the end of the first fruiting cycle, roots of deblossomed ‘Tribute’ had a higher percentage of total nonstructural carbohydrates (TNSC) than roots of fruiting plants. In Expt. 2, ‘Tribute’ plants were grouped into fruiting and deblossomed treatments. At 7-day intervals throughout the fruiting cycle, Pn, specific leaf weight (SLW), and chlorophyll content were determined for a leaf that was fully expanded at bloom (old leaf) and for the most recently expanded leaf (young leaf) of each plant. Pn of the young leaf was greater for fruiting plants than deblossomed plants only during weeks 5 and 6 of the fruiting cycle, and no treatment effect was observed for old leaf Pn. During fruit maturation, SLW was higher for deblossomed plants than fruiting plants for both leaf ages. Deblossomed plants had a higher leaf chlorophyll content than fruiting plants during the 1st, 2nd, and 4th weeks of the fruiting cycle.
Leaf gas exchange of avocado (Persea americana Mill.) and mango (Mangifera indica L.) trees in containers and in an orchard (field-grown trees) was measured over a range of photosynthetic photon fluxes (PPF) and ambient CO2 concentrations (Ca ). Net CO2 assimilation (A) and intercellular partial pressure of CO2 (Ci) were determined for all trees in early autumn (noncold-stressed leaves) when minimum daily temperatures were ≥14 °C, and for field-grown trees in winter (cold-stressed leaves) when minimum daily temperatures were ≤10 °C. Cold-stressed trees of both species had lower maximum CO2 assimilation rates (Amax ), light saturation points (QA ), CO2 saturation points (CaSAT ) and quantum yields than leaves of noncold-stressed, field-grown trees. The ratio of variable to maximum fluorescence (Fv/Fm ) was ≈50% lower for leaves of cold-stressed, field-grown trees than for leaves of nonstressed, field-grown trees, indicating chill-induced photoinhibition of leaves had occurred in winter. The data indicate that chill-induced photoinhibition of A and/or sink limitations caused by root restriction in container-grown trees can limit carbon assimilation in avocado and mango trees.
The effects of applied N and shading duration on net gas exchange and growth of two southern Florida cassava (Manihot esculenta Crantz.) cultivars grown in containers were determined. Both cultivars responded similarly to shading and N with respect to the measured variables. There were no interactions between shading duration and N application rate for any of the variables measured. Tissue dry weights, total leaf N and chlorophyll concentrations, net CO2 assimilation (A), transpiration (E), water-use efficiency (WUE), and stomatal conductance (gs) were quadratically related to the concentration of N applied to the soil. The optimum N application rate for maximum growth of both cultivars was 60 mg/plant per day. Increased shading duration reduced A, E, gs, WUE, storage root number, and weight and increased the shoot : root ratio.