Cultivation strategies to avoid malfunctioning stomata under high air humidity conditions in greenhouse production. Meseret T.

Transcription

1 Cultivation strategies to avoid malfunctioning stomata under high air humidity conditions in greenhouse production Meseret T. Terfa

2 BACKGROUND Saving energy is an important goal in greenhouse production To reduce the ventilation is a way to save energy but the air humidity will in certain periods be high - >85% Reduce the stomatal functioning, which will not close in darkness will not close in dry air 2 In several plant spp. it has been shown that RH >85 % result in poor post harvest life due to poorer water control

3 BACKGROUND Different techniques have been tested to avoid malfunctioning stomata: Increasing temperature/reducing RH during some hours each day Varying VPD, CO 2 and light intensity Light quality Application of ABA

4 Manipulation of stomata Eg. A short (6 hour) temperature increase (21 C 27 C) during the day or variation in the vapor pressure deficit (VPD) can trigger the stomata closure (Pettersen et al. 2007, Mortensen et al. 2007). However, the time and the magnitude of the temperature and\or VPD variation the plant must experience to develop functional stomata has not been investigated Also, it is not known if temperature and VPD variation work via the same or via distinct physiological mechanisms 4

5 Manipulation of stomata Besides, using of different light quality in stomata opening and closure of some commercial plants has been studied Yet, it is not known if the light quality responses can overcome the negative effect of high RH on stomata function Thus, studying effects of light quality, alone and in combination with VPD fluctuations to improve our understanding on how the climate during growth can control stomata function and general stress tolerance of plants has great importance 5

6 Abscisic acid regulation under high RH Tabell 1. Målinger under moderat og høy relativ luftfuktighet (RF) av ABA og bundet form (ABA-GE) og aktiviteten til enzymet som er ansvarlig for å frigjøre ABA tilbake til fri form. Resultatene viser hvordan ABA nivået øker i mørke i planter dyrket ved moderat RF, men forblir lavt i planter dyrket ved høy RF. Moderat RF (60%) Høy RF (90%) Lys Mørke Lys Mørke ABA (fri form) ABA-GE (bundet form) Enzymaktivitet (β-glukosidase)

7 Aim of the study Hence based on the above background we designed different experiments as follows: 1. How elevated growing temperatures and air humidity fluctuations control stomata function and stress tolerance of plants 2. To study interactions between relative air humidity and light climate on the growth performance and quality of roses To determine the stomatal sensitivity to humidity in light and darkness (photoperiod) To determine the stomatal sensitivity to humidity in different light qualities

8 Experiment I High relative air humidity and continuous light reduce stomata functionality by affecting the ABA regulation in rose leave High Relative humidity (90 %) Irradiance: 100µmol Temp: 1±20 20 hrs of mercury light 4 hrs of Dark (22:00-18:00) (18:00-22:00) Moderate Relative humidity (60 %) Irradiance: 100µmol Temp: 1± hrs of mercury light 4 hrs of dark (22:00-18:00) (18:00-22:00)

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10 Figure 1. Diurnal stomata conductance (mol m -2 s -1 ) measured on the adaxial side of the first fully expanded leaves with five leaflets of rose plants grown at moderate (60%) or high (90%) relative air humidity (RH). 85% reduction in conductance in moderate RH during dark 28.5% reduction in conductance in high RH during dark

11 Figure 2: Relative weight (A) and transpiration rate (B) of leaves of rose plants grown under moderate (60%, black) or high (90%, white) relative air humidity (RH) during 3 h of desiccation

12 Conclusion from Experiment I Plants under high RH have higher transpiration both during growth and during desiccation stress, and that there is no stomata response to darkness High ABA in low humidity during dark Hence, a dark period and reduced RH (<85%) are important for the development of functional stomata

13 Experiment II: Stomata response to humidity and a short temperature increase Experimental setup Treatments Temperature ( o C) RH (%) > 32(2 hours) -> > 55 -> 95

14 Relative weights UNIVERSITETET FOR MILJØ- OG BIOVITENSKAP Experiment II: Results Fig 1. Relative weight of leaves of A. thaliana plants grown under different relative air humidity (RH) and temperature treatment during 3 h of desiccation Temp High RH Low RH Time after detachment (in minutes)

15 Conclusions: A short temperature (2hrs) increase during day improves stomata functionality compared to high RH Plants given the temperature increase still have large stomata, but better stomatal functionality than stomata developed in continuous high RH

16 Experiment III Effect of light quality (high blue light proportion) on stomata functionality of rose plants grown under high RH High Relative humidity (90 %) Irradiance: 100µmol Temp: 1±20 20 hrs of LED/HPS 4 hrs of Dark Moderate Relative humidity (60 %) Irradiance: 100µmol Temp: 1± hrs of LED/HPS 4 hrs of Dark

17 Preliminary Results from Experiment III Fig 1: Relative weight of leaves of rose plants grown under different relative air humidity (RH) and light quality during 3 h of desiccation Relative Weight (%) LED-60%RH LED-90%RH HPS-90%RH HPS-60%RH Time after detachment (minutes)

18 Fig 2. Diurnal stomata conductance (mol m -2 s -1 ) measured on the adaxial side of the first fully expanded leaves with five leaflets of rose plants grown at relative air humidity (RH) regimes and light quality Stomata conductance mol m -2 s HPS-60 HPS-90 LED-60 LED Time of day

19 Tabell 3. Transpirasjonsrate (mmol m-2 s-1) målt med porometer (AP4 leaf porometer, DeltaT devices) i lysfasen og 1 time etter start av mørkeperioden for Rosa x hybrida Toril dyrket ved høy relativ luftfuktighet (RF) under SON-T eller LED (20% blått og 80% rødt) 20 timer per dag (4 timer mørke)i vekstkammer. Målingene er utført på fullt utviklede blader. Moderat RF (60%) Høy RF (90%) Lys Mørke Lys Mørke SON-T LED (20% blå, 80% rød)

20 On going experiments.. High Relative humidity: (90 %) Irradiance: 100µmol Temp: 1±20 20 hrs of LED with 100% R 4 hrs of Dark Low Relative humidity (90 %) Irradiance: 100µmol Temp: 1± hrs of LED with 90% R: 10% B 4 hrs of Dark

21 On going experiments.. High Relative humidity: (90 %) Irradiance: 100µmol Temp: 1±20 20 hrs of LED with 80% R: 20% B 4 hrs of Dark Low Relative humidity (90 %) Irradiance: 100µmol Temp: 1± hrs of LED with 100% B 4 hrs of Dark

22 Thank you for your attention!