Agriculture Reference
In-Depth Information
(ambient+300, and ambient+600 µmolmol−1 CO
2
) resulted in high fruit
dry matter, fructose, glucose and total sugar contents and low citric and
malic acid contents. High CO
2
growing conditions significantly enhanced
the fruit content of ethyl hexanoate, ethyl butanoate, methyl hexanoate,
methyl butanoate, hexyl acetate, hexyl hexanoate, furanol, linalool and
methyl octanoate. Thus, the total amounts of these compounds were high-
er in berries grown in CO
2
-enriched conditions than those grown in ambi-
ent conditions. The highest CO
2
enrichment (600 µmolmol−1) condition
yielded fruit with the highest levels of these aroma compounds.
The positive effects of elevated CO
2
in the fruit-storing environment
have been established. One of the most notable effects of high CO
2
levels
in postharvest handling is to inhibit ethylene binding and action competi-
tively hence delaying ripening in climacteric fruits (Kanellis at al., 2009).
High CO
2
will directly inhibit succinate dehydrogenase, thus impairing the
functioning of the tricarboxylic acid cycle and aerobic respiration. There
are numerous physiological disorders that can be attributed to high CO
2
stress, including black heart of potatoes (Davis, 1926), brown heart or core
in apples and pears (Meheriuk et al., 1994), surface bronzing in apples
(Meheriuk et al., 1994) and brown stain of lettuce (Kader and Saltveit,
2003). High CO
2
can also modulate chilling stress, ethylene induced dis-
orders and susceptibility to pathogenic attack (Kader and Saltveit, 2003).
17.3.3 RAINFALL
The majority of horticultural industries have a dependence on irrigation,
and very little rain grown production occurs. Rainfall has positive and
negative effects on horticultural production. When 'normal in-season'
rainfall events occur, irrigation storages (dams and aquifers) are replen-
ished, and the amount of irrigation required to grow crops is reduced. 'Out
of season' rainfall events, especially if high in intensity, often have devas-
tating consequences for product quality and production. All horticultural
regions will continue normal production for extended periods as droughts
develop. This situation has occurred in many horticultural regions for a
number of years without significant rainfall, which produces storage re-
plenishing runoff. This is in direct contrast with much of the broad-acre
and grazing industries, which depend on preplanting and in-crop rainfall
to produce economic yields.
