Base-line Growth Studies of ‘Grand Rapids’ Lettuce in Controlled Environments1

‘Better Bush’ tomato (Lycopersicon esculentum Mill.) plants were grown in small- (450-cm3) or large-(13,500-cm3) volume plastic containers and harvested every 2 weeks from time of planting until 12 weeks, at which time ripe fruits had developed. Plants were fertilized three to six times daily to prevent drought and nutrient stress. After only 2 weeks, there were significant reductions in total height, node number, leaf area, and dry weight of leaves. By 4 weeks, dry weights of stems and roots were also significantly less in small pots than in large pots. These differences were maintained for the next 10 weeks. Root restriction also generally caused an increase in root : shoot ratio. Roots in small-volume containers formed a highly branched mat, whereas those in large-volume containers had long taproots and showed little branching. Root restriction also significantly reduced the total number and fresh and dry weight of mature fruits. Despite these differences, both groups of plants had nearly 41% of the total photosynthate in the reproductive portion of the plant after 12 weeks of treatment. During weeks 6–8, the mean relative growth rate of plants in small pots was twice that in large pots but thereafter was only half as much. Restricting root volume had little or no effect on net assimilation rate. These data suggest that, for a given growing area, a culture system using small containers would be more efficient in producing fruit for a given weight and size of plant than one using large containers. These findings have important implications for growers and researchers involved in growing plants in confined spaces such as in a phytotron or controlled ecological life support system (CELSS).

Section: Methodsmentioning

confidence: 99%

Restricted Root Zone Volume: Influence on Growth and Development of Tomato

Ruff

Krizek

Mirecki

et al. 1987

“…No supplemental aeration was needed to maintain vigorous and healthy root systems. The modified Hoagland's solution used was previously reported (7).…”

Section: Methodsmentioning

confidence: 99%

“…Light energy was supplied by a combination of cool-white fluorescent and incandescent lamps, supplying about 10,300 and 2,500 W of input power, respectively. At the start of each experiment, the light level was adjusted to 325 |xmol s_1m"2 PPF (400-700 nm) ± 12%, a specified experimental standard (7). Near IR light was adjusted to 8.0 W m 2 in a 70 nm waveband centered at 780 nm.…”

Section: Growth Chambers and Microprocessor Two Walk-in Growthmentioning

confidence: 99%

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Growth and Productivity of ‘Grand Rapids’ Lettuce in Diurnally Fluctuating Temperatures and Day/night Average Temperatures

Miller

Langhans

1985

The feasibility of utilizing different patterns of air temperature changes over the light and dark periods was investigated to provide a basis for greenhouse energy conservation. ‘Grand Rapids’ lettuce was grown hydroponically in microprocessor controlled growth chambers, under a light level of 325 µmol s-1m-2 PPF. Air temperatures were: a) increased from 15° to 35°C (late-peak), b) decreased from 35° to 15° (early-peak), and c) increased to 35°, then back to 25° (mid-peak) during the 16-hr light period. The late and mid-peak patterns had a gradual decrease in night air temperature, whereas the early peak pattern had a gradual increase in night air temperature. Each of these patterns averaged 25° during the light period, and 20° during the dark period. “Early-peak” plants grew poorly, whereas plants grown under the mid- and late-peak regimes grew well. Early morning diffusive resistance was similar for early- and mid-peak plants. Transpiration rates followed the air temperature changes.

“…RH was 75% ± 5% in the light and 80% ± 6% in the dark. Four times each day each pot received about 100 ml of nutrient solution (8) in which the Ca concentration was 10 ~4m.…”

Section: Methodsmentioning

confidence: 99%

Effects of Relative Humidity and Root Temperature on Calcium Concentration and Tipburn Development in Lettuce

Collier

Tibbitts

1984

Self Cite

Growth chamber studies were undertaken with a tipburn-sensitive cultivar of romaine lettuce (Lactuca sativa L. cv. Lobjoits Green Cos) grown under a photosynthetic photon flux density of 320 μmol s−1m−2 for 16 hours; light and dark temperatures were 26.0° and 12.5°C, respectively. As the relative humidity (RH) during the light period was decreased from 74% to 51%, growth was retarded, Ca concentration increased, and the onset of tipburn delayed. Decreasing RH during the dark period from 95% to 90% reduced growth and resulted in lower CA concentrations and earlier tipburn development. Further decreases from 90% to 65% caused no additional change in growth or tipburn response. Root temperatures of 23.5°, compared with 15.0°, slightly increased Ca concentration but induced earlier tipburn development. Ca concentrations were increased and tipburn delayed by humidity conditions which provided large diurnal fluctuations in water potential in the plant and which encouraged root pressure flow during the dark period. Elevated root temperatures did not provide expected increases in Ca accumulation in young leaves.