Agriculture Reference
In-Depth Information
temperatures, and thus at least partially offsetting the temperature effects
of supra-optimal temperatures on yield (Polley, 2002).
Higher temperatures can increase the capacity of air to absorb water
vapor and, consequently, generate a higher demand for water. Water stress
is of great concern in fruit production, because trees are not irrigated in
many production areas around the world. It is well documented that water
stress not only reduces crop productivity but also tends to accelerate fruit
ripening (Henson, 2008). Exposure to elevated temperatures can cause
morphological, anatomical, physiological, and, ultimately, biochemical
changes in plant tissues and, as a consequence, can affect growth and de-
velopment of different plant organs. These events can cause drastic reduc-
tions in commercial yield. However, by understanding plant tissues physi-
ological responses to high temperatures, mechanisms of heat tolerances
and possible strategies to improve yield, it is possible to predict reactions
that will take place in the different steps of fruit and vegetable crops pro-
duction, harvest and postharvest (Kays, 1997).
Photosynthetic activity is proportional to temperature variations. High
temperatures can increase the rate of biochemical reactions catalyzed by
different enzymes. However, above a certain temperature threshold, many
enzymes lose their function, potentially changing plant tissue tolerance to
heat stresses (Bieto and Talon, 1996). Pome and stone fruits require a spe-
cific amount of winter chilling to develop fruitful buds and satisfactorily
break dormancy in the spring. Increasing minimum temperatures under
climate change may induce insufficient chilling accumulation resulting in
uneven or delayed bud break. Color development in apples occurs through
the production of anthocyanin. Anthocyanin production is reduced by high
temperatures.
Simulations have shown that temperature influences processes in-
volved in fruit growth at the sink level, that is, fruit demand and growth
rate. The contribution of temperature to fruit demand can be associated
with the daily variation in degree-days used to compute fruit demand in
the model of mango growth in dry mass (Léchaudel et al., 2005a). It has
been suggested in other species, including Satsuma mandarin (Marsh et
al., 1999) and apples (Austin et al., 1999), that temperature may affect the
rate of cell division. Other preharvest factors such as resource limitation
during cell division due, for example, to carbon competition, can be a
source of variation of the initial fruit dry mass (Léchaudel and Joas, 2007).
