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  • Author or Editor: Marc-J. Trudel x
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Abstract

An increase in soil temperature from 14.0 to 21.8°C increased total yield of greenhouse tomatoes (Lycopersicon esculentum L. cv. Vendor) by 47% in the spring under warm air temperature conditions, but a rise in soil temperature from 13.8 to 20.5° increased tomato yield by only 5% in the fall. Under plastic tunnel conditions (low air temperature), heating soil increased total yields by 36% in the spring and 42% in the fall.

Open Access

Abstract

Greenhouse tomato plants (Lycopersicon esculentum Mill. cv. Vendor) were grown at 5 root temperatures (12°, 18°, 24°, 30°, and 36°C) and 4 night air temperatures (12°, 15°, 18°, and 21°) for 3 months. Low root and low night air temperatures contributed to high root dry weight. However, under warm soil temperature conditions (30° and 36°), roots were most efficient in sustaining shoot growth and in absorbing water as indicated by the percentage of shoot dry weight. Shoot growth was maximum at 15° night air temperature and 30° root temperature. High root temperatures are required at low night air temperature for maximum shoot growth. Maximum yields were obtained at a combination of 18° night air temperature and 24° root temperature. An increase in soil temperature partly offsets the detrimental effects of low night air temperatures.

Open Access

Abstract

Tomato plants (Lycopersicon esculentum Mill. cv. Vendor) were maintained at 5 root temperatures (12°,18°, 24°, 30°, and 36°C) and 4 night air temperatures (12°, 15°, 18°, and 21°) for a period of 3 months. Although N content of the shoots was increased at 24° and 30° root temperatures, a reduction of this element was measured in the 4th fully expanded leaves. An increase in root temperature from 12° to 24° increased P, K, Mg, Ca, Fe, and Mn content of leaves, but had the opposite effect on Na. High night temperature (21°) favored the absorption of Ca and Na but reduced the concentration of P in the leaves. The results indicate that fertilization of tomato plants should be adapted to root and night air temperatures to avoid excessive vegetative growth and flower abscission and to maximize yield.

Open Access

Abstract

Ten-week-old pepper plants (Capsicum annuum L. ‘Bell Boy’) were grown at 5 different root-zone temperatures (RZT) (12°, 18°, 24°, 30°, or 36° ± 2°C) for a period of 8 weeks. Maximum shoot dry weight and leaf area were measured at 24° and 30° RZT. Leaf area ratio (LAR) was not significantly affected by RZT treatments. Fruit weight was maximum at 30° RZT, but earliness was delayed at high RZT. Nitrogen, P, and K content of shoots were increased, but Mg and Ca concentrations were reduced at high RZT. Plant photosynthesis was the highest at 36° RZT. Increasing RZT improved both greenhouse or outdoor pepper production.

Open Access

Abstract

Tomato plants (Lycopersicon esculentum Mill. cv. Carmello) seeded on 3 Dec. 1984 and 17 Jan. and 8 Mar. 1985 were grown under natural or supplementary lighting (high-pressure sodium) of 100 μ·mol·s−1·m−2 (photosynthetically active radiation) from pricking out to transplanting. Plants of the first, second, and third seeding dates grown under supplementary lighting had at transplanting dry weights 6.6, 3.5, and 2.5 times higher, respectively, than plants grown under natural light. The number of leaves formed below the first inflorescences was reduced significantly with supplementary lighting, which also reduced the incidence of flower abortion. Supplementary lighting increased early marketable yields for the 3 Dec. seeding by 100% (from 0.77 to 1.55 kg/plant) and total yields by 10% (from 3.55 to 3.91 kg/plant). No significant differences between lighting treatments could be observed in early and total yields of plants from the last seeding date.

Open Access

Abstract

Four cultivars of greenhouse cucumber (Cucumis sativus L. ‘Corona’, ‘Far-biola’, ‘Pandex’, and ‘Sandra’) were grown under four lighting conditions: natural light and natural light supplemented by 100, 200, or 300 μmol·s−1·m−2 provided by high-pressure sodium lamps for a photoperiod of 18 hr. For this purpose, transplants were first seeded on 24 Sept. 1984, transplanted on 23 Oct., and grown according to the successive cropping method. Supplemental lighting enhanced plant growth and increased yield. Our data indicate that a marketable yield of 240 fruit/m2 per year of greenhouse cucumbers could be obtained with supplementary lighting of 300 μmol·s−1·m−2.

Open Access

Abstract

Tomato plants (Lycopersicon esculentum Mill. cvs. Vendor and Carmelo) were exposed to two CO2 levels (330 or 800 µl·liter−1) and five root-zone temperatures (12°, 18°, 24°, 30°, or 36°C). The enhancement of shoot growth from CO2 enrichment increased with root-zone temperature (RZT) to 30°. Enhancement of root growth decreased. The response to high CO2 level was larger with ‘Vendor’ than ‘Carmelo’. A concentration of 800 µl·liter−1 of CO2 increased N and K uptake by 58% and 45%, respectively. The largest P uptake was obtained with plants grown at 800 µl·liter−1 CO2 and 36° RZT. Leaf NO 3 ¯ concentration decreased at 800 µl·liter−1 of CO2 and at a RZT of 12°. At low RZT, CO2 enrichment increased growth but did not increase the translocation of NO 3 ¯ to the leaf. There was no significant relationship between nitrate reductase activity (NRA) and leaf NO 3 ¯ content, implying that the “inactive NO 3 ¯ ” (which does not affect NRA) was at higher levels in leaves exposed to 330 µl·liter−1 CO2 than in those exposed to 800 µl·liter−1 CO2. There was also a decrease in N concentration of leaves subjected to 800 µl·liter−1 CO2, possibly caused by a reduction in NO 3 ¯ transport toward leaves rather than a decrease in NO 3 ¯ reduction within leaves. Therefore, the best response to CO2 enrichment at 30° appears to be related to increased NO 3 ¯ translocation.

Open Access

Lycopersicon esculentum Mill. cv. Vedettos and Lycopersicon chmielewskii Rick, LA 1028, were exposed to two CO2 concentrations (330 or 900 μmol·m-3) for 10 weeks. The elevated CO2 concentration increased the relative growth rate (RGR) of L. esculentum and L. chmielewskii by 18% and 30%, respectively, after 2 weeks of treatment. This increase was not maintained as the plant matured. Net assimilation rate (NAR) and specific leaf weight (SLW) were always higher in C02-enriched plants, suggesting that assimilates were preferentially accumulated in the leaves as reserves rather than contributing to leaf expansion. Carbon dioxide enrichment increased early and total yields of L. esculentum by 80% and 22%, respectively. Carbon exchange rates (CER) increased during the first few weeks, but thereafter decreased as tomato plants acclimated to high atmospheric CO2. The relatively constant concentration of internal C0 with time suggests that reduced stomatal conductance under high CO2 does not explain lower photosynthetic rates of tomato plants grown under high atmospheric CO2 concentrations. Leaves 5 and 9 responded equally to high CO2 enrichment throughout plant growth. Consequently, acclimation of CO2-enriched plants was not entirely due to the age of the tissue. After 10 weeks of treatment, leaf 5, which had been exposed to high CO2 for only 10 days, showed the greatest acclimation of the experiment. We conclude that the duration of exposure of the whole plant to elevated CO2 concentration, rather than the age of the tissue, governs the acclimation to high CO2 concentrations.

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