
TY  - JOUR
A1  - Allaway, WG 
A1  - Austin, B 
A1  - Slatyer, RO 
T1  - Carbon Dioxide and Water Vapour Exchange Parameters of Photosynthesis in a Crassulacean Plant, <I>Kalanchoe daigremontiana</I>
JF  - Functional Plant Biology
JO  - Functional Plant Biol.
Y1  - 1974
VL  - 1
IS  - 3
SP  - 397
EP  - 405
KW  - 
UR  - https://doi.org/10.1071/PP9740397 
N2  - In 16-h days and under a 26/19&#176;C day/night temperature regime, leaves of K. daigvemontiana took up CO2 in the daytime as well as at night. Daytime net CO2 uptake was in two periods: an initial one about 5 h long, in which net uptake rose to a maximum and then fell to near zero; and, after a period in which stomata were closed and CO2 exchange did not take place, a second period of net uptake. In this second period net uptake rose rapidly to a steady rate which was maintained for about 8 h until the end of the day. In this period, mean rate of light-saturated photosynthesis in normal air was 25 ng cm-2 s-1; maximum obtainable photosynthesis rate averaged 87 ng cm-2 s-1 at this time. These values are considerably lower than those to be expected for C3 plants. The internal resistance to CO2 uptake averaged about 8 s cm-l. In normal air, leaf resistance to water vapour diffusion averaged about 8.5 s cm-1 in the steady period of photosynthesis. Both these resistances are higher than those often reported for C3 plants, and may explain the low photosynthetic rates. The CO2 compensation point during the period of steady photosynthesis was about 51 &#956; 1/1 (92 ng cm-3). This value, together with some biochemical evidence from pulse-chase experiments, suggests that photosynthesis in the last 8 h of the light period follows a C3-type pathway. 
ER  -

