ISHS Acta Horticulturae 711: V International Symposium on Artificial Lighting in Horticulture
LETTUCE TRANSPLANT GROWTH IN RESPONSE TO MEDIA SURFACE COLOR |
| Authors: | M.G. Karlsson, J.W. Werner |
| Keywords: | Lactuca sativa, seedling development, light quality, morphology, hypocotyl length, red/far-red ratio |
| Abstract:
A lettuce (Lactuca sativa) transplant suitable for mechanical transplanting, handling and field establishment is compact with a well-developed root system and short hypocotyl. The purpose of this study was to record potential benefits of mulch or other cover materials during early lettuce transplant development to accommodate desirable adjustments in transplant morphology. Pelleted seed of the cultivar ‘Alpha’ was placed directly on the surface of a moist peat-lite medium and covered with a thin layer of additional medium (5 mm) or perlite (8 mm) or a single layer of white or black surfaced plastic film with 5 mm large openings for seedling emergence. At the time of seeding, the pots were placed in a greenhouse environment of 18°C and 16-h photoperiod at 10 d-1mol-2. Lettuce seeded and covered with white plastic had significantly shorter average hypocotyl length at 5.2 mm after 14 days. The longest hypocotyl (11.0 mm) was recorded for seeds covered with black plastic. Lettuce grown on peat-lite medium had hypocotyl length of 10.7 mm. Perlite covered seed resulted in transplants with 6.4 mm long hypocotyl. Overall transplant height after 14 days, was similar for white plastic, peat-lite and perlite grown seedlings at 7.3 to 7.4 cm. Black plastic resulted in significantly taller seedlings of 9.1 cm. Independent of covering material, all seedlings averaged six expanded true leaves after 14 days. These results suggest white plastic mulch or perlite could aid production of compact lettuce transplants with short hypocotyl length. | |
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