The second fundamental process – breathing provides energy for various
biochemical processes of synthesis associated with growth, the construction of new
structural elements of plants and transport of substances, as well as the support of vital
structures of plant organs. In this case, the organic substances accumulated in the
organs of plants are consumed.
The third fundamental process is growth. Photosynthesis and growth are
considered as interrelated processes. Energy provision of growth function by way of
photosynthesis is a prerequisite for growth. The system of donor-acceptor relations is
the main manifestation of the integration of photosynthesis and growth at the level of
the whole organism. Between the donor and the acceptor, temporary intermediate funds
of assimilates are formed. The funds can be found in each organ, but more mobile ones
are likely to be found in leaves and stems. Reserve assimilates, for a longer period, are
mostly accumulated in the roots.
The process of leaf photosynthesis is divided into two stages: diffusion of CO
2
molecules from the air to the centers of carboxylation in the cell which is described by
the laws of biophysics, and the biochemical cycle of photosynthesis in chloroplasts
which is described by the laws of photobiology and biochemistry [14].
To describe the diffusion of CO
2
molecules in the leaf, Gaastra applied the Fick
law:
,
r
r
r
c
-
c
md
sc
ac
C
A
+
+
=
L
Ф
(4)
where Ф
L
is photosynthetic rate, мg СО
2
·сm
-2
·с
-1
; c
A
& C
C
are СО
2
concentrations, respectively, in the air and in carboxylation centers, мg СО
2
·сm
-3
; r
ac
,
r
sc
, r
md
are diffusion resistance to CO
2
molecules, respectively, in the boundary layer
of the leaf, stomata and mesophilic cells.
The biochemical cycle of photosynthesis is described by the Michaelis-Menten
equation:
,
c
r
I
a
1
1
c
mx
Ф
Ф
+
=
Ф
Ф
(5)
where а
Ф
is initial slope of the light curve of photosynthesis; I
Ф
is PAR intensity;
χ
Ф
is PAR absorption coefficient by the leaf; r
mx
is carboxylation effective resistance.
To assess the dependence of photosynthesis intensity on the luminous flux
density, there exist many different formulas, but most often leaf photosynthesis is
described by the Monse and Saeko’s formula
,
max
max
j
o
ф
ф
ф
ф
І
а
Ф
І
а
Ф
Ф
+
=
(6)
where Ф
j
о
is photosynthesis intensity under optimal conditions of heat and
moisture in real conditions of illumination; Ф
мах
is photosynthesis intensity at light
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