Composition of the shoot tissue of lettuce changes with environment. Light intensity or daily light integral affects the concentrations of nitrate, sugars, and other metabolites in various leafy green vegetables, including lettuce and spinach
Greenhouse production of coleus generally occurs between the months of February and May in the United States to coincide with spring bedding plant sales. Mean outdoor daily light integrals (DLIs) at this time of year in the northeastern United
( left ) compared with a sunny day ( right ) as measured by a quantum sensor. The four photoperiod (12, 15, 18, and 21 h) treatments all had a daily light integral of 12 mol·m −2 ·d −1 . Rudbeckia fulgida can be difficult to germinate with variable
Daily light integral is a measure of the total photosynthetic photon flux ( PPF ) density delivered over the course of 1 day. This measurement has proven to be an extremely useful tool for assessing the irradiance delivered to various horticultural
decreased by 1.1 nodes as the DLI increased to 17.2 mol·m −2 ·d −1 ( Table 1 ). There was no effect of DLI on the node number below the terminal inflorescence of K. lacinitata and K. velutina ( Table 1 ). Table 1. Effect of daily light integral (DLI) on
, which includes Korea, the northern half of the United States, and Europe), the mean photosynthetic daily light integral (DLI) can be a limiting factor in the production of many greenhouse crops during the winter and early spring ( Faust, 2003 ). The DLI
. Sowing and harvest dates, mean photosynthetic photon flux ( PPF ) provided by high-pressure sodium lamps, shadecloth percentage, mean daily light integral (DLI), and leaf and air temperatures during 5 weeks of Tecoma stans seedling propagation. Effects
Growers of leafy greens in mid-latitude (40–50°) high tunnels who wish to extend their growing season past mid-autumn are faced with two significant challenges: low air temperatures, primarily at night, and low daily light integral (DLI) due to
, whereas the daily light integral inside the greenhouse averaged 16.8 ± 4.9 mol·m −2 ·d −1 (means ± sd ). Temperature and relative humidity were measured using a humidity and temperature probe (HTO-45; Rotronic, Huntington, NY) and photosynthetic photon
, production begins in June, when liners are transplanted to small containers for bulking. During this time, the ambient outdoor daily light integral (DLI) is 35 to 65 mol⋅m −2 ⋅d −1 ( Faust and Logan, 2018 ); however, growers may need to deploy shade curtains