Patent ID: 12185680

DETAILED DESCRIPTION OF THE EMBODIMENTS

FIG.1Aschematically depicts an embodiment of a horticulture lighting arrangement1000. The arrangement1000comprises a lighting system100configured to provide horticulture light101to a plant1, e.g. a Basil plant1, the horticulture light101having a controllable spectral power and spectral power distribution, and a control system300configured to control the spectral power and spectral power distribution of the horticulture light101.

The horticulture lighting arrangement1000comprises one or more light generating devices. Here, by way of example the horticulture lighting arrangement1000comprises first light generating devices110and second light generating devices120. The former is configured to generate first device light111, and the latter is configured to generate second device light121. The horticulture light101may comprise one or more of the first device light111and the second device light121.

The horticulture lighting arrangement1000may especially be configured to provide (in an operational mode of the horticulture lighting arrangement1000) the horticulture light101according to an on-off schedule wherein consecutively an on-period D and an off-period N are applied.

The horticulture light101comprises one or more of first horticulture light1011comprising a wavelength selected from the range of 400-600 nm, red light1012comprising a wavelength selected from the range of 600-700 nm, and far-red light1013comprising a wavelength selected from the range of 700-800 nm. As schematically depicted, in this embodiment the first light generating device110is configured to generate first device light111comprising far-red light1013, and a second light generating device120configured to generate second device light121comprising one or more of first horticulture light1011and red light1012. Other embodiments may also be possible. For instance, the first device light111may also comprise (some) red light1012and the second device light121may also comprise (some) far-red light1013.

The on-period D may in embodiments last in in the range of 12-20 hours. The off-period N may in embodiments last in the range of 4-12 hours. Especially, the on-period D comprises an end-of-day period EOD at the end of the on-period D. This end-of-day period EOD lasts in embodiments in the range of 0.5-4 hours. Further, during at least part of the on-period D before the end-of-day period EOD a R/Fr ratio, defined as a ratio I600-700 nm/I700-800 nmof red light1012and far-red light1013, may especially be selected from the range of 4-20. Further, in embodiments during at least part of the end-of-day period EOD the R/Fr ratio may be selected from the range of 0.1-4. Especially, the end-of-day period EOD lasts in embodiments in the range of at least 1 hour.

Hence, in specific embodiments during the on-period D before the end-of-day period EOD a contribution of the first device light111to the horticulture light101(comprising one or more of the first device light111and the second device light121) may be less than 10%, and during at least part of the end-of-day period EOD a contribution of the first device light111to the horticulture light101(comprising one or more of the first device light111and the second device light121) may be at least 20%.

As indicated above, the fact that during the EOD period there is far-red light does not exclude the presence of also other types of light, like red light. Likewise, the fact that during the on-period part preceding the EOD period there is one or more of first horticulture light and red light (which may together be PAR light), does not exclude the presence of other types of light, like far-red light. Hence, in embodiments during part of the end-of-day period EOD first horticulture light1011, red light1012, and far-red light1013are provided.

Reference h1indicates a height above a substrate20(or average substrate surface, such as water, soil, etc.). This height or distance is measured from a light emitting surface115or exit surface of a light generating device. The distance is indicated with reference d, which is for the light generating devices110,120which are configured above the plants1the same as the height h1.

FIG.1Aalso schematically depicts an embodiment of a horticulture system2000, especially for a plant, such as more especially for a Basil plant1. The horticulture system2000especially comprises an indoor facility2100. Further, the horticulture system2000comprises the horticulture lighting arrangement1000as defined herein. In embodiments, the horticulture lighting arrangement1000may especially be configured to provide the horticulture light101in the indoor facility2100, especially for growing of the (Basil) plant1.

In embodiments, the horticulture system2000comprises a plurality of light generating devices110, configured at different first heights h1of the light emitting surfaces115(or exit surfaces) above the substrate20; see e.g. inFIG.1Athe light generating devices110above and next to the plant(s)1. As indicated above, in embodiments the lighting system100may comprise the first light generating device110, which may especially be configured to generate at least part of the far-red light1013. The first light generating device110may comprise a light emitting surface115(see also above), of which during operation far-red light1013emanates. In the operational mode the contribution of far-red light1013to the horticulture light101during the end-of-day period EOD may be controlled as function of the first heights h1of the light emitting surfaces115above the substrate20. Hence, in embodiments the method may (further) comprise controlling (in the operational mode) the contribution of far-red light1013to the horticulture light101during the end-of-day period EOD as function of a position of the corresponding light generating device110relative to a canopy of the Basil plant1to which the far-red light1013is provided.

Especially, the horticulture lighting arrangement1000is configured to provide during the on-period D the horticulture light101with an average intensity selected from the range of at least 50 μmol/m2/s, especially selected from the range 100-600 μmol/m2/s at a distance d from the light generating devices110,120of the lighting system100of at least 30 cm. Further, in embodiments the horticulture light101during at least part of the on-period D before the end-of-day period may comprise 5-20% of the photons in wavelength range of 400-500 nm, 0-30% of the photons in wavelength range of 500-600 nm, 50-95% of the photons in wavelength range of 600-700 nm, and 0-6% of the photons in wavelength range of 700-800 nm, with the aggregate contribution of photons from different wavelength ranges not exceeding 100%. Yet further, in embodiments the horticulture light101during at least part of the end-of-day period EOD may comprise 0-10% of the photons in wavelength range of 400-500 nm, 0-15% of the photons in wavelength range of 500-600 nm, 0-80% of the photons in wavelength range of 600-700 nm, and 20-100% of the photons in wavelength range of 700-800 nm, with the aggregate contribution of photons from different wavelength ranges not exceeding 100%.

As indicated above, in the operational mode the contribution of far-red light1013to the horticulture light101during the end-of-day period EOD is controlled as function of one or more of a growth time, a growth phase or age of one or more plants1, and a canopy density (defined by one or more plants1). A way to estimate the canopy density is e.g. a shadow measurement.

FIGS.1B-1Cschematically depict a non-limiting number of embodiments of the day-night horticulture lighting scheme, with D indicating providing horticulture light (day-period), and N indicated essentially not providing horticulture light (night period). The horticulture light101that is mainly used for growing may be indicated as grow light GL.

This horticulture light101may comprise one or more of first horticulture light1011comprising a wavelength selected from the range of 400-600 nm and red light1012comprising a wavelength selected from the range of 600-700 nm. Optionally, however, see alsoFIG.1C, this grow light may comprise far-red light1013(comprising a wavelength selected from the range of 700-800 nm). During essentially the last part of the day period, (additional) far-red light1013may be provided. This may partly overlap in time with the time grow light is provided, though this is not necessarily the case. After the far-red EOD period, the night period N may commence.

Hence,FIGS.1B-1Cschematically depict an embodiment of a method of providing horticulture light (to a Basil plant) wherein the method comprises: providing during a controlling mode horticulture light101(to the Basil plant1, seeFIG.1A) according to an on-off schedule wherein consecutively an on-period D and an off-period N are applied. The horticulture light101comprises one or more of first horticulture light1011comprising a wavelength selected from the range of 400-600 nm, red light1012comprising a wavelength selected from the range of 600-700 nm, and far-red light1013comprising a wavelength selected from the range of 700-800 nm. Further, the on-period D may last in in the range of 12-20 hours and the off-period N may last in the range of 4-12 hours, wherein the on-period D comprises an end-of-day period EOD at the end of the on-period D. Yet further, during at least part of the on-period D before the end-of-day period a R/Fr ratio, defined as a ratio I600-700 nm/I700-800 nmof red light1012and far-red light1013, is selected from the range of 4-20, and during at least part of the end-of-day period EOD the R/Fr ratio is selected from the range of 0.1-4. Especially, the end-of-day period EOD may last in the range of 0.5-4 hours.

As schematically depicted inFIGS.1B-1C, during part of the end-of-day period EOD first horticulture light1011, red light1012, and far-red light1013may (also) be provided. Likewise, some far-red light1013may also be available during the part of the day period preceding the EOD.

FIGS.1B-1Conly depict a single cycle. Such cycles may (continuously) be repeated during one or more weeks, especially a plurality of weeks (see alsoFIG.1E).

FIG.1Dschematically depicts a spectral powder distribution of an embodiment of horticulture light101. Of course, completely other spectral power distributions may also be possible. Here, by way of example essentially all types of horticulture light mentioned herein are available, including first horticulture1011light which may have intensity in the blue and/or green, especially at least blue, red light1012, which may have intensity in the red, and far-red light1013, which may have intensity in the far-red. During the day period, the spectral power distribution of the horticulture light may substantially change when moving from the period preceding EOD into the EOD period.

Whether or not EOD light is applied, may also depend upon the growth stage, growth time or age of the plant. This is very schematically depicted inFIG.1E. Here, an embodiment is schematically depicted of a method comprising growing the Basil plant over a growing period t, wherein t may in embodiments be at least three weeks, and wherein the method may further comprise applying during a first part of the growing period t during the entire on-periods D horticulture light101having a R/Fr ratio of at least 4 (see schematically the first three days D), and applying during a second part of the growing period t during at least part of the end-of-day periods EOD the horticulture light101having the R/Fr ratio selected from the range of 0.1-4 (see schematically the second three days D). The height of the bars and the width of the bars are not on scale, and are only schematically.

Basilicum(Ocimum basilicumL.) is a culinary herb, which can provide aroma. People use the aroma of fresh leaves in food to adjust the flavor. During the storage process, basil easily gets a chilling injury when the temperature is lower than 12° C. Chilling injuries are seen as a dark spot on the leaf, wilting and loss of aroma. This invention relates amongst others to a method for optimizing the use of far-red light to induce chilling resistance on basil plant during their growth with an optimum light sequences such that energy is saved and unnecessary far-red exposure inducing unwanted physiological changes on the plant is achieved.

Applying short day photoperiod (<15 h) versus long day (18 h) may improve also sometimes the chilling resistance. However, a long day photoperiod is most beneficial for a grower as the grower than would make most beneficial use (in terms of hours of use) of the lighting system he has installed. Applying far-red during all day. on the other hand, may lead toBasilicumstretching too much (under this prolonged exposure to far-red) but it would improve the chilling resistance of theBasilicum.

When planting in high density for optimizing the growth and light use efficiency, a natural shading of the plant canopy occurs and therefor enable towards the end of the growth a low R:FR ratio on the plants. Therefore a dynamic dosing of far-red could take into account the natural R:FR variation due to the canopy in order to reduce energy usage of far-red light during the growth. Camera or sensor aided light control would enable a direct adjustment of the light level (red or far-red) in order to maintain the R:FR dose on the plant leaves.

Amongst others of Cinnamon, Dolly, Emily, and Lemon cultivars were tested. These all showed an increase in chilling resistance, especially when relatively longs days were applied, such as at least 14 hours, even more especially at least 16 hours. Cinnamon cultivar appeared to be extremely responsive to far-red.

Experimental Evidence

Determining the R:FR Range

Support for the range of low R:FR range of 0.1 to 4 is provided as follows and based on the following considerations. Far-red wavelengths are known to signal the presence of shade to plants which triggers a specific behavior of the plants and leaves. When growing plants in a farm, plant density—in terms of number of plants per area—may lead to the creation of shades in a canopy as the plants grow.FIG.2Billustrated the effect of canopy size on the the creation of shadows underneath the canopy top. The left pictures inFIG.2Bare taken at position C (camera position) as indicated in the left part ofFIG.2A. The pictures as the right inFIG.2Bare taken at a position near the substrate indicated as the lower position S (sensor position) in the left part ofFIG.2A. When measuring light transmission in a canopy, the first thing noticed is that, as you lower the sensing position into the crop (see lower position S in the left part ofFIG.2A), the Photosynthetic Active Radiation light level (PAR light, covering the wavelengths ranging from 400-700 nm) strongly decreases. This decrease is stronger and more abrupt with higher plant density. The second thing to notice is that this decrease in intensity is much less for far-red light (which is in the range between 700-800 nm). This is because of the low leaf absorption and high leaf transmission of wavelengths above 700 nm. This means that as the plant canopy is growing, the R:FR ratio perceived by thebasilicumcanopy, especially at lower locations in the canopy, is changing over time. The right part ofFIG.2Ashows the changes in measured R:FR ratio at the bottom of the canopy as a function of plant growth (horizontal axis represents time in terms of days of growth) for two different planting densities.

State of the art horticulture lighting apparatus may comprise a small amount of far-red (5% to 7%) and as a result provide a R:FR ratio of 10 or more. The inventors have seen thatBasilicumgrown under these conditions is sensitive to chilling. In order to significant improve the chilling resistance, the inventors have found that the R:FR ratio needs to be lowered, i.e. the amount of far-red needs to be increased. The shade naturally occurring in a canopy during growth creates a de facto R:FR ratio for the lower leaves of 6 or 4 (see right part ofFIG.2A) depending on planting density. It has been found that the lower leaves of harvestedBasilicumplants grown at high planting densities, i.e. leaves that have experienced substantial shadow periods wherein increased far-red is present, showed improved chilling resistance. Therefore, the inventors consider an amount of additional far-red in the horticulture light corresponding with a R:FR ratio of 4 as a minimum amount to achieve a chilling resistance effect inBasilicum. Therefore, in order to have a significant effect on chilling resistance the R:FR ratio should be bellow 4. As most of the currently available far-red light sources, such as far-red LED, also have some of their spectral power in the red part of the spectrum, i.e. the tail of the spectral distribution of the far-red LED towards the red wavelengths, there is always a small amount of red providing by the far-red LED and hence the maximum amount of far-red as expressed in a R:FR ratio of the horticulture light is 0.1, being the minimum R:FR ratio achievable.

Effect of End-of-Day Far-Red on Chilling Resistance of Basil: Cultivar Lemon

Basil cultivar Lemon was used in this experiment. Seeds were sown manually in soil trays at a density of 1000 plants per m2. Once the seeds were sown, the seed trays were covered with plastic film to keep 100% humidity and placed in darkness at 20° C. to induce germination. Two days after the sowing, the seedlings were transferred to a growth cell and illuminated under 180 μmol/m2/s of horticulture light with a red-blue LED spectrum (RB 180) in a photoperiod of 18 hours. The temperature was 24° C., and relative humidity 70%. Irrigation was applied every 24 hours, using a fixed ebb-flood system. Seven days after the sowing, the plastic films were removed. Twelve days after the sowing, the plants were transplanted to rockwool blocks of 7*7 cm, and the plant density was 100 plants per m2.

A control group of plants (also referred to as the DRW Fr group) was illuminated with a control horticulture light having a light intensity of 232 μmol/m2/s and a deep red+white+far-red spectrum (DRW Fr 232 μmol: 11% blue, 18% green, 71% red, 7% Far-red) during an on-period of 18 hours. The control horticulture light had a R:FR ratio of 10. An experimental group (also referred to as the EOD Fr group) of plants was illuminated using a dynamic EOD-Fr light recipe comprising the same horticulture light conditions as the control group during the first 17 hours in the on-period and additional far-red at an intensity of 164 μmol/m2/s during a three-hour end-of-day with one hour overlap with DRW Fr of the first 17 hours of the on-period, the additional far-red enabling a R:Fr ratio of 1, followed by only far red ration in hour 19 and 20, enabling a R:Fr ratio of 0.1.FIG.3Aillustrated the horticulture light recipe used in the control group and the EOD Fr group.

Sixteen days after the transplanting and subjected to the lighting conditions as set out above, the plants were harvested and some of the harvest was kept in a storage to measure shelf life and chilling resistance. It is to be noted that the total additional far-red light used in the experimental group relative to the control group added up to 28 moles in total during the entire growth cycle of theBasilicum.

The overall visual quality (OVQ) of theBasilicumleaves was measured during storage on 10 samples in the control group and 10 samples in the experimental group. The concept of overall visual quality (OVQ) measurement is described in article “Systems for Scoring Quality of Harvested Lettuce” by Kader et al. and is available on http://ucce.ucdavis.edu/files/datastore/234-417. pdf. The samples were stored at 4° C. with a relative humidity of 65%. Overall visual quality was taken every two to three days, scoring according to a scale from 2-9. A customer acceptance threshold was set at score 6 on that same scale. When a sample got below that score, it is considered unsellable however assessments were nonetheless continued. The results are shown inFIGS.3B(graphical) and3C (pictures).FIG.3Cshows that the plants grown under DRW Fr experience significant chilling injury (darkening of the leaves) already starting at day 5 of storage whereas the plants treated with EOD Fr do not show chilling injury.

Effect of End-of-Day Far-Red on Chilling Resistance of Basil:Cultivars Cinnamon and Dolly

Cultivar Cinnamon and Dolly were used for this experiment. Light settings were identical as in the experiments described above with respect to the cultivar Lemon. The results on overall visual quality (OVQ) during storage are shown inFIG.4Afor Cinnamon andFIG.4Bfor Dolly.

Effect of End-of-Day Far-Red with a Ratio R:Fr˜4

Cultivar Piccolino was used for this experiment. A control of these plants was illuminated with a horticulture light having a light intensity of 300 μmol/m2/s and a deep red+white+Fr spectrum (DRW Fr: 11% blue, 18% green, 71% red, 7% Far-red) in an on-period of 15 hours. The control horticulture light had a R:Fr ratio of 10. The experimental EOD-Fr light recipe comprised the same horticulture light condition as the control group during the first 14 hours of the on-period and a three-hour far-red light at an intensity of 50 μmol/m2/s was added with one hour overlap in hour 15 with the DRW Fr preceeding the end-of-day period, enabling a R:Fr ratio of 4, and then followed by only far-red light in hours 16 and 17, enabling a R:Fr ratio of 0.1.

Some plants from each of the treatment groups, i.e. the control group and the EOD-Fr group, where harvested at their grow temperature of 24° C. and other plants from each of the treatment groups were harvested at a lower temperature of 16° C. while also grown on 24° C. It is known that the Piccolino cultivar is more sensitive to temperature than otherBasilicumcultivars. The results show that harvesting temperature had a mild effect on the chilling injury and that a significant effect of the EOD Fr application is observed in both cases. The results are depicted inFIGS.5A(harvesting temperature 24° C.) and5B (harvesting temperature 16° C.).

Effect of Pre-Harvest Application of Far Red on Chilling Resistance ofBasilicumCV Emily

Cultivar Emily, was grown in the same way as cultivar Lemon explained above. However, after the plants had been transplanted into their final grow environment they were exposed to horticulture light at an intensity of 150 μmol/m2/s and a deep red+white spectrum DRW having 11% blue, 18% green, 71% red, 1% far-red. The control horticulture light had a R:Fr ratio of 70 and was applied with a photoperiod of 16 h per day on-period. Next to the control group, who did not receive additional far-red during growth, there was also a second group receiving additional 180 μmol/m2/s of far-red light during the whole on-period during a period of 3 weeks before harvest and a third group receiving the additional 180 μmol/m2/s of Far-red light during the whole on-period only during a period of 1 week before harvest. The additional far-red (on top of the DRW) resulted in a R:Fr ratio of 0.65. The results inFIG.6show that there is a strong improvement of shelf life (due to chilling resistance) with 5 to 6 days. This also shows that a week of pre-harvest far-red treatment is almost as good as 3 weeks pre-harvest far-red treatment. This suggest that the chilling resistance is especially created in the last week before harvest. In such week the total amount of additional far-red applied is 70 moles. In comparison, the EOD far-red experiments discussed earlier used 28 moles.

It is therefore more advantageous to use the EOD far-red concept to increase chilling resistance than the ‘whole day’ far-red during the week before harvest to save energy, as far-red LEDs are not very efficient in terms of energy consumption. The duration of the end-of-day period is a trade-off between a minimum duration to achieve an increase in chilling resistance and a maximum duration taking into account energy consumption (which is relatively high for far-red LEDs) and elongation of the plant as a result of the far-red.