Both types of far-red light
absorbing photoselective filters reduced height of all species tested in
preliminary trails but the magnitude of height reduction varied with the
species. (Table 2 and
2). In general, watermelon seedlings showed the greatest height
reduction followed by bell peppers, tomato, and chrysanthemum. Number of
leaves was not affected, indicating that height reductions were caused
by shorter internodes. The height reduction increased as the dye concentration
in the panels increased but total shoot dry weight was reduced because
of the severe light reduction as the dye concentration increased. Therefore,
a dye concentration that gives a light transmission of 75% was selected
for photoselective film production and further experimentation.
Table 2. Effect of dye concentrations in YBM-1 and YBM-10 photoselective
chambers on height of chrysanthemum, watermelon, bell pepper, and tomato
plants. The number followed by the film indicates the percent light transmission
through the panels. Percentage height reductions compared to control plants
are given in parentheses.
|Plant height (cm)|
|YBM-1 #85||26.6 (-10)||21.7 (-24)||17.2 (-22)||-|
|YBM-1 #75||23.7 (-20)||14.6 (-49)||13.9 (?37)||-|
|YBM-1 #65||20.9 (-30)||14.5 (-49)||13.9 (-37)||-|
|YBM-1 #55||21.8 (-27)||14.9 (-48)||12.0 (-46)||-|
|YBM-10 #85||31.0 (+3)||38.9 (-26)||11.2 (-23)||32.5 (-7)|
|YBM-10 #75||25.9 (-14)||38.1 (-27)||10.0 (-31)||23.2 (-34)|
|YBM-10 #65||26.2 (-13)||35.0 (-33)||9.9 (-31)||23.4 (-33)|
|YBM-10 #55||27.0 (-11)||33.2 (-37)||9.6 (-34)||23.7 (-32)|
(image: Response bell pepper (top), tomato (center), and cucumber (bottom) seedlings to photoselective films.) Based on initial findings, photoselective greenhouse films with red and far-red light absorbing films (SXE-4 and YXE-10 films, respectively) were produced with a dye concentration that results in a 75% light transmission ( light spectrum (image) of two types of films). Growth of several vegetable transplants and ornamental bedding plants was evaluated inside growth chambers covered with these films. The results are summarized in Table 3. Plants produced under the far-red light absorbing film were, in general, shorter (except snapdragon and miniature roses) than the control plants while plants produced under the red light absorbing film had similar or increased height compared to the control plants. The magnitude of height reduction varied with the species and cultivar.
We also evaluated flowering
of selected ornamental crops inside the chambers under natural short day
conditions. Flowering of miniature rose plants was not affected (Table
3). Flowering of cosmos, zinnia, and chrysanthemum (short day plants) was
slightly delayed (by 1-2 days) under the far-red light absorbing film.
Photoselective films had the greatest influence on flowering of snapdragon
and petunia (long-day plants). Flowering of these species was delayed by
7-13 days under the far-red light absorbing films. Red light absorbing
film did not significantly affect flowering of these species tested.
Table 3. Influence of red and far-red light absorbing plastic
films (SXE-4 and YXE-10, respectively) on plant height and flower development
(days to anthesis, DA) under natural short days of selected crops. Control
is a clear polyethylene film.
|Control film||SXE-4 film||YXE-10 film|
|Cucumber ‘Sweet Success’||17.3 b||-||19.8 a||-||8.6 c||-|
|Tomato‘Mountain Pride’||15.0 a||-||15.8 a||-||11.2 b||-|
|Bell pepper ‘Capistrano’||11.1 a||-||11.4 a||-||8.4 b||-|
||48.3 b||63 b||53.8 a||61 b||48.9 b||70 a|
||25.5 a||51 b||24.7 ab||50 b||23.0 b||59 a|
|Florida pink||23.6 b||26 a||27.2 a||27 a||22.5 b||25 a|
|Florida blue||31.2 a||30 a||30.4 a||28 a||27.9 b||31 a|
|Florida sky blue||26.7 ab||30 a||28.1 a||30 a||23.4 b||32 a|
||-||53 b||-||54 b||-||66 a|
||24.5 b||33 ab||28.4 a||32 b||18.8 c||35 a|
||38.0 a||35 c||40.9 a||36 b||30.4 b||37 a|
|‘Sonata White’||37.3 a||26 a||38.1 a||27 a||33.5 b||27 a|
|‘Cherry Cupido’||28.8 a||46 a||29.2 a||46 a||27.2 a||46 a|
|‘Bright Golden Anne’||32.6 b||64 a||34.6 a||65 a||28.4 c||65 a|
|‘Iridon’||22.6 b||59 a||25.8 a||60 a||19.8 c||62 a|
|‘Yellow Snowden’||50.8 a||55 a||50.4 a||57 a||40.7 b||56 a|
|Pachystachys lutea||30.1 b||38 a||32.8 a||38 a||27.0 c||38 a|
|Strobilanthes dyerianus||34.2 ab||-||38.9 a||-||30.2 b|
Response of Petunia and Snapdragon (long day plants) to photoselective films.
Response of Zinnia and Cosmos to photoselective films.
Response to 'Iridon' (top), 'Bright Golden Anne' (center), and 'Yellow Snowdon' (bottom) chrysanthemums to photoselective films.
Response to Strobilanths (top) and Pachystachys (bottom) to photoselective films.
Photoselective greenhouse films with red and far-red light absorbing films (SXE-4 and YXE-10 films, respectively) produced with a dye concentration that results in a 75% light transmission.