The effects of time and intensity of supplemental blue lighting during morning twilight on growth and physiological performance of cucumber seedlings.
Cucumbers (Cucumis sativus L. cv. Naoyosi) were grown hydroponically at air temperatures of 28/24 degrees C (D/N) and photosynthetic photon flux (PPF) of 300 micromoles m-2 s-1, in a walk-in type growth cabinet equipped with 3-band fluorescent lamps. Plants were subjected to supplemental blue lighting applied daily just before the 14-h photoperiod (morning twilight) under PPFs of 0, 10, 30, 100, and 200 micromoles m-2 s-1. Treatment periods were 0, 5, 30, or 120 min. Growth and morphological parameters were measured after 12 and 14 days of treatment. On the 13th day of treatment, the stomatal conductance (gs), transpiration rate (Tr), and net photosynthetic rate (Pn) were measured under 3-band fluorescent lamps at a PPF of 200 micromoles m-2 s-1. After 17-19 days of treatment, changes in Pn effected by supplemental blue light were measured continuously for 30 min. Treatment with 5 min of blue lighting promoted more growth than treatment for 30 or 120 min. Similarly, gs, Tr, and Pn were the greatest in plants grown with supplemental blue light of 30 micromoles m-2 s-1 and 100 micromoles m-2 s-1 PPF for 5 min. Pn in plants grown under blue light of 30 micromoles m-2 s-1 for 5 min increased by 60% compared with that of control plants. Pn rose and was maintained at a higher level with 5-min blue lighting treatment. Supplemental lighting with blue light in the morning twilight is considered to be effective for seedling growth, and can be utilized for bionursery facilities to increase efficiency of plant production.
Sung
I K
IK
College of Agriculture, Osaka Prefecture University, Sakai, Japan. sung@bansui.ige.tohoku.ac.jp
Kiyota
M
M
Hirano
T
T
D018553:Cucumis sativus / Q000254:growth & development* / Q000502:physiology / Q000528:radiation effects*; D004307:Dose-Response Relationship, Radiation; D004780:Environment, Controlled; D008027:Light; D017440:Photoperiod; D010788:Photosynthesis / Q000502:physiology / Q000528:radiation effects*; D018515:Plant Leaves / Q000254:growth & development / Q000502:physiology / Q000528:radiation effects; D018526:Plant Transpiration