THE PHOTOSYNTHETIC QUOTIENT 



33 



Table 3.1 

 The Photosynthetic Quotient (Qp = AO2/— ACO2) and the Respiratory 



Quotient (Qr = ACO2/- AO2) 



Species 



Ailanthus 



Aspidistra 



Begonia 



Cherry laurel 



Kidney bean (young) 



Pea 



Ricinus 



Sorrel 



Wheat 



Average (27 spp.) : 



Sambucus nigra 



Pelargonium zonale 



Sambucus nigra 

 Aesculus hippocastanum 

 Ilex aquifolium 



Leucobryum glaucum 



Hormidium flaccidum 

 Chlorella pyrenoidosa 

 Nitzschia closterium 



Nitzschia palea 



Observer" 



M.D. 

 M.D. 

 M.D. 

 M.D. 

 M.D. 

 M.D. 

 M.D. 

 M.D. 

 M.D. 

 M.D. 



W.St. 



W.St. 

 W.St. 



W.St. 

 W.St. 



W.St. 



W.St. 



W.St. 



v.d.P. 



M.S.D.D, 



B. 



Remarks 



B. 



B. 

 B. 



25° C, 5% CO2, illumi- 

 nated for 5 hrs., 45,000 

 lux 



Same after 12 hrs. in dark 



25° C; 2 hrs., 45,000 lux, 



low O2 (2%) 

 Same after 3.5 hrs. in dark 

 85° C, 45,000 lux, 6.5% 



CO2, 4.5 hrs. 

 10° C, 45,000 lux, 6.5% 



CO2 

 Leathery leaves, Qp > 1 



according to Bonnier 



and Mangin 

 Moss, 25° C, 5% CO2, 



22,000 lux 

 Alga (green) 

 Green alga, low light 

 Diatom, high light, 



12-31° C. 

 Same, low light, 



12-28° C. 

 Diatom, high light 

 Same, low light 



Qp 



1.02 

 1.00 

 1.03 

 0.97 

 1.12 

 1.00 

 1.03 

 1.04 

 1.02 

 1.04 



1.00-1.05 

 0.98-1.02 



1.01-1.02 

 1.01 



1.00-1.01 

 0.99-1.02 



1.00 



1.01 



0.92-1.07 



0.98* 



1.04 ±0.03 



1.07 ±0.02 

 1.03 ±0.03 



1.05 ±0.02 



Qr 



1.08 

 0.94 

 1.11 

 1.03 

 1.12 

 1.07 

 1.03 

 1.04 

 1.03 

 1.05 



0.93 ±0.04 



0.79 ±0.03 



" M.D. = Maquenne and Demoussy (1913); W.St. = Willstatter and Stoll (191S); v.d.P. = van der 

 Paauw (1932); B. = Barker (1935); M.S.D.D. = Manning, Stauffer, Duggar and Daniels (1938). 



6 Average of 18 single determinations of quantum yields of photosynthesis by simultaneous measure- 

 ments of ACO2 and AO2; single values varying from 0.3 to 1.5. 



In the same year, 1864, in which the correct value of the photosyn- 

 thetic quotient was first determined by Boussingault, a direct proof of the 

 formation of carbohydrates by photosynthesis was given by Sachs, who 

 observed the growth of starch grains in the chloroplasts of photosyn- 

 thesizing leaves. However, not all plants form starch after intense 



