Agriculture Reference
In-Depth Information
climate conditions and the crop manage-
ment practices.
The postharvest storage conditions are
more linked to the genetic characteristics of
the cultivar and to the mineral nutrition
than to the climatic conditions during the
crop cycle (Urban, 1997a). Good posthar-
vest management in all the links of the dis-
tribution chain is of utmost importance to
ensure that the product has the proper qual-
ity when it gets to the consumer.
by means of cultural practices and
proper agronomic management (prun-
ing, thinning, fertilization, climate
control). Of all the climate factors,
temperature is the main tool to mani-
pulate the distribution of biomass.
Light and CO
2
do not have direct
effects in the partition of biomass,
although their availability influences
photosynthesis.
Radiation is the main factor determin-
•
ing bioproductivity, together with the
radiation intercepted by the canopy,
the efficiency in the conversion of inter-
cepted radiation into biomass and res-
piration losses.
The crop characteristics (arrangement
6.11
Summary
•
Growth is a consequence of a positive
carbon balance. That is, when the net
photosynthesis (difference between
gross photosynthesis and respiration) is
positive.
Gross photosynthesis is determined by
•
of the plants and the plant rows, leaf
area) and of the greenhouse (transmis-
sivity to radiation, radiation diffusion)
affect the amount of intercepted radia-
tion and its efficiency of use.
In the short term, growth mainly
•
the PAR, which is the main limiting
factor of the productive process. The
CO
2
concentration in the air is the main
factor to optimize the efficiency in the
use of the intercepted PAR. The influ-
ence of temperature in photosynthesis
is limited, except when it reaches
extreme values.
The boundary layer (static air layer sur-
•
depends on photosynthesis and respi-
ration (carbon balance) and the water
status of the plant.
In the long term, the productive process
•
is determined by the accumulation of
dry matter and by plant development,
by the distribution of dry matter to the
organs which are going to be harvested
and by the quality of the product.
The greatest effect of radiation on growth
•
rounding the leaf) is very thick inside a
greenhouse due to the absence of wind,
and may have a notable effect limiting
photosynthesis, if there is not a minimum
air movement inside the greenhouse.
Suboptimal conditions for photosyn-
•
is through photosynthesis. Temperature
affects leaf growth, primordial develop-
ment in young crops, and respiration,
basic for the carbon balance.
The positive effect of CO
•
thesis involve irreparable losses of
potential yield.
Photomorphogenesis is the effect of radia-
•
2
on growth is
important. The effect of ambient humid-
ity is limited, except when extreme
values occur.
Given conditions of an appropriate pho-
•
tion on plant development. The majority
of morphogenic responses are controlled
by the pigment phytochrome. Among
these responses is photoperiodism.
Respiration is quantitatively important
•
toperiod, water supply and nutrition,
the development rate depends mainly
on temperature. The thermal integral
received from a certain moment deter-
mines, in many cases, the beginning of a
certain stage of development.
The capacity of the plants to integrate
•
in the carbon balance. Primarily it
depends on temperature, increasing
with it, so its control is fundamental to
optimize the net photosynthesis (car-
bon balance).
The distribution of assimilates must be
•
•
temperature fluctuations in periods larger
than 1 day (24 h) may allow for more effi-
cient management: for instance, using
oriented towards the maximization of
the biomass in the harvestable organs,
