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Abstract

Butterhead lettuce (Lactuca sativa L. ‘Montana’) plants were grown in recirculating solution culture in growth chambers under various combinations of day temperatures (TD; 12°, 15°, 19.5°, or 22.5°C) and night temperatures (TN; 5° or 14°) and root-zone temperature (TR; 20°, 23°, 26°, or 29°) Photosynthetic photon flux (PPF) was 3.8 mol·day−1·m−2. Leaf area and weight were determined at 7-day intervals. The final harvest followed 28 days of treatments. There were no significant interaction effects between TD and TN. An increase of TD from 12° to 19.5° increased fresh and dry leaf weight and leaf area at final harvest, but increasing TN from 5° to 14° had little effect. Specific leaf area and leaf area ratio increased with increasing TD and TN. Leaf weight ratio increased with TD but remained constant with TN. The overall effect of TR on plant size was minor. Dry weight of roots decreased with increasing TR at the 14- and 21-day harvests, but fresh and dry leaf weights were not affected. Leaf area increased with TR up to 26°. Increases in TR resulted in increased values for specific leaf area, leaf area ratio, and leaf weight ratio at final harvest. The results suggest that some butterhead lettuce cultivars may be grown satisfactorily under low daily PPF by allowing TN to decline to 5° while maintaining TD at ≈ 19°C. In ‘Montana’, increasing TR above 20° under those conditions had little beneficial effect on plant size at harvest.

Open Access

The aim of this work was to study different apple of somatic material as callus and adventitious shoots are concerned, for further utilization in the research of somaclonal variation. The somatic materials were: leaf discs, cotyledons and hypocotyls of Gala apple seedlings, cultivated in a MS medium added by B5 vitamins in addition to (in mg/l): BAP (1,0), NAA (0,5) mio-inositol (100,0) sucrose (30,0 g/l) and solidified in agar (6,0 g/l). The several times of explant exposition to the dark affected the final callus weight. Callus weight derived from leaf discs were higher than those for cotyledons and hypocotyls. Explants exposed directly under light or up to two weeks in the dark showed less percentage of regenerative callus as compared to those of three weeks in the dark. The leaf explants presented the highest percentage of regenerative callus. The least response was obtained for those derived from hypocotyls. The highest number of adventitious shoots was obtained keeping the explants three weeks in the dark as compared to directed light exposition.

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peak in 1 to 2 h, and then gradually decreased. This phenomenon may indicate that much of the net CO 2 fixation may occur early in the light period. The original light–dark cycle was 24 h·d −1 with 12 h light and 12 h dark on 27 to 29 Aug. 2012. By

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Doritaenopsis Tinny Tender, in which net CO 2 uptake rate declined with increasing period of drought and had a sudden revival after rewatering ( Cui et al., 2004 ). However, up to the present, there has been no research related to the effects of long-term dark

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require a long, uninterrupted dark period to induce flowering; this dark period is considered to be more important than the light period itself ( Lumsden and Vince-Prue, 1984 ). Cultivators have found success with flowering cannabis under a 12.0-h dark

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; FAOSTAT, 2009 ) and the demand for watermelon seedlings (≈33 billion per year in China), seedling storage is essential for meeting market demands. The most common method of preserving seedlings for a short-term period is low-temperature storage in darkness

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Star) and lily ( Lilium hybrida cv. Yellow Overlord) stems under alternating light and dark regimes during their vase period. Materials and Methods Plant materials Cut rose ( Rosa hybrida cv. Movie Star) and lily ( Lilium hybrida cv. Yellow Overlord

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continuous dark (31.3 ± 4.4%), continuous light (32.7 ± 2.6%), and alternating light (30.5 ± 3.8%) conditions ( Fig. 3C ). For the same storage period, percentage germination of opercula-removed seeds showed no significant difference at PPFD ranging from 0

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two repetitions. During the 7-d postgrafting period, there was an interaction between heat and dark treatments for average and maximum air temperatures ( Table 1 ). Healing chambers subjected to the heat treatment had higher maximum air temperatures

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reduction in dark respiration ( Nemali and van Iersel, 2004 ; Xu et al., 2004 ). However, supplemental light is mainly used during the dark period of the year where light conditions during the day and nights are low and the increase in photosynthesis with

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