MGRox
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- Aug 6, 2014
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I found another little paper abstract that ties into some of the suggestions made earlier relating to photosystem damage.
http://link.springer.com/article/10.1007/BF00194455
"Nitrate caused a rapid, but transient inhibition of the rate of net CO2 assimilation,....."
"Nitrite or ammonium feeding resulted in decreased rates of CO2 assimilation for as long as the nitrogen source was supplied"
"In all cases the degree of inhibition was greatest at high irradiance and least at low irradiance, even though the total amino-acid contents of the leaves were comparable at the time when maximum inhibition of CO2 assimilation occurred."
"Measurements of chlorophyll-a fluorescence showed that the quantum efficiency of PSII decreased and non-radiative dissipation of excitation energy increased as CO2 assimilation was inhibited by nitrate or nitrite. These metabolites had no direct effect on thylakoid PSII-based electron transport."
**The first couple points are mainly of interest that Nitrate, Nitrite and Ammonium all DECREASE CO2 assimilation!!
**It is very important to note that "the degree of inhibition was greatest at high irradiance". I.E more light nets lower assimilation!!
***finally and relating directly to photosystem damage, is the last point. "non-radiative dissipation of excitation energy increased as CO2 assimilation was inhibited" <<< As shown previously Calcium is required to "quench" this dissipation to prevent PSII damage.
Last I believe I have been able to re-create // witness the same effect and similar scenario as the OP. These pics are of the same plant (Fuel at appx week 6). One side of the plant was facing a 600w Hortilux HPS. The other side of the plant was facing a Gavita DE 600/750 (set on 600). Distance from light to plant on both sides was equal. (plant was stretched directly under gavita to eliminate burning variable).
First is the side of the plant facing the Hortilux 600w.
Second pic is from the same plant, same height and same time, but is the side facing the Gavita 600/750
IMHO PSII damage / repair was in excess on the Gavita facing side leading to destructive photosystem damage. While on the Hortilux side it was manageable to stay non-destructive. (Higher Ca when leaf was formed [appx wk 3] most likely would have averted this effect).
http://link.springer.com/article/10.1007/BF00194455
"Nitrate caused a rapid, but transient inhibition of the rate of net CO2 assimilation,....."
"Nitrite or ammonium feeding resulted in decreased rates of CO2 assimilation for as long as the nitrogen source was supplied"
"In all cases the degree of inhibition was greatest at high irradiance and least at low irradiance, even though the total amino-acid contents of the leaves were comparable at the time when maximum inhibition of CO2 assimilation occurred."
"Measurements of chlorophyll-a fluorescence showed that the quantum efficiency of PSII decreased and non-radiative dissipation of excitation energy increased as CO2 assimilation was inhibited by nitrate or nitrite. These metabolites had no direct effect on thylakoid PSII-based electron transport."
**The first couple points are mainly of interest that Nitrate, Nitrite and Ammonium all DECREASE CO2 assimilation!!
**It is very important to note that "the degree of inhibition was greatest at high irradiance". I.E more light nets lower assimilation!!
***finally and relating directly to photosystem damage, is the last point. "non-radiative dissipation of excitation energy increased as CO2 assimilation was inhibited" <<< As shown previously Calcium is required to "quench" this dissipation to prevent PSII damage.
Last I believe I have been able to re-create // witness the same effect and similar scenario as the OP. These pics are of the same plant (Fuel at appx week 6). One side of the plant was facing a 600w Hortilux HPS. The other side of the plant was facing a Gavita DE 600/750 (set on 600). Distance from light to plant on both sides was equal. (plant was stretched directly under gavita to eliminate burning variable).
First is the side of the plant facing the Hortilux 600w.
Second pic is from the same plant, same height and same time, but is the side facing the Gavita 600/750
IMHO PSII damage / repair was in excess on the Gavita facing side leading to destructive photosystem damage. While on the Hortilux side it was manageable to stay non-destructive. (Higher Ca when leaf was formed [appx wk 3] most likely would have averted this effect).