This paper describes the CO
2 concentration in tissue culture vessels and the net photosynthetic rates of tissue cultured plantlets in the closed vessels with stopper.
Firstly, this paper shows changes with passage of time in CO
2 concentration in the closed vessels containing plantlet (s) cultured under usual conditions. Secondly, it gives the estimated net photosynthetic rates of plantlets cultured in the closed vessels. Lastly, it estimates the effects of CO
2 enrichments on the photosynthetic rate of one of the plantlets used.
The plantlets used were 8 genera of ornamental foliage, and had grown large enough to pot. The CO
2 concentration was measured by using a gas chromatograph.
In order to estimate the photosynthetic rates of the plantlets in the closed vessels, a model of CO
2-net photosynthesis was developed, and the parameters of the model were estimated on the basis of the measured values of the CO
2 concentration in the closed vessels.
The model is given by the following equation:
P
n=P
ns⋅[1-exp {-G/P
ns⋅(K
c-C)}]
where
Pn is the net photosynthetic rate [μcm
3 CO
2 mg
-1 h
-1],
Pns the saturated net photosynthetic rate for CO
2 concentration [μcm
3 CO
2 mg
-1 h
-1],
G the gradient of CO
2-net photosynthesis curve at CO
2 compensation concentration [μcm
3 CO
2 mg
-1 h
-1 vpm
-1],
Kc the CO
2 concentration in the closed vessel [vpm], and
C the CO
2 compensation concentration [vpm].
Pns,
G and
C are the parameters of this model.
The results can be summarized as follows:
(1) In all closed vessels, the CO
2 respired in the dark period was accumulated to the concentration level from about 3000 to 9000vpm. One or two hours after the start of the light period, the CO
2 concentration in the vessels are rapidly decreased to less than 90vpm by the photosynthesis of plantlets. Thus, it became clear that all plantlets have photosynthetic ability under the light period.
(2) The plantlets could not fully achieve their photosynthetic capacity, because the CO
2 concentration in the closed vessels were too low in most of the light period.
(3) Estimated net CO
2 uptake per day of all plantlets in the closed vessels were negative. This means that the plantlets had grown by using sucrose in the media as the main source of carbonhydrate.
(4) The results of the estimation on the effects of CO
2 enrichment indicate that net photo-synthetic rate of a plantlet may be increased not only by increasing the inside CO2 concentration, but also by increasing the outside concentration or by increasing the number of air changes of the vessel when the outside concentration is higher than that of inside during the light period.
The above results indicate that tissue cultured plantlets in the closed vessels can be grown photoautotrophically during and after the multiplication stage by improving the CO
2 and light environments in the closed vessels.
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