Question

Describe & explain why the effect of temperature as a

Answer 1

Answer:

Although  the  light  dependent  reactions  of photosynthesis     are    not     affected     by changes in temperature, the light independent   reactions  of   photosynthesis are dependent  on  temperature.  They  are reactions  catalysed  by  enzymes.  As  the enzymes approach their optimum temperatures  the  overall  rate  increases.  It approximately   doubles   for   every   10°C increase    in    temperature.    Above    the optimum  temperature  the  rate  begins  to decrease, as enzymes are denatured, until it stops.

Explanation:

At  low  light  intensities,  as  light  intensity increases,the  rate of  the  light-dependent reaction,and   therefore   photosynthesis generally, increases proportionately (straight    line    relationship).    The    more photons  of  light  that  fall  on  a  leaf,  the greater     the     number     of     chlorophyll molecules  that  are  ionised  and  the  more ATP   and   NADPH   are   generated.   Lightdependent  reactions  use  light  energy  and so    are    not    affected    by    changes    in temperature.As light intensity is increased further, however, the rate of photosynthesis is eventually  limited by some other factor. So the rate plateaus. At very high light intensity, chlorophyll may be damaged and the rate drops steeply (not shown in the graph).Chlorophyll ais used in both photosystems. The wavelength of light is also important. PSI absorbs energy  most  efficiently  at  700  nm  and  PSII  at  680  nm.  Light  with  a  higher  proportion  of  energy concentrated in these wavelengths will produce a higher rate of photosynthesis.An    increase    in    the    carbon    dioxide concentrationincreases  the  rate  at  which carbon  is  incorporated  into  carbohydrate in  the  light-independent  reaction,  and  so the    rate    of    photosynthesis    generally increases until limited by another factor.As    it    is    normally    present    in    the atmosphere  at  very  low  concentrations (about  0.04%),  increasing  carbon  dioxide concentration  causes  a  rapid  rise  in  the rate  of  photosynthesis,  which  eventually plateaus   when   the   maximum   rate   of fixation is reached.