Agriculture Reference
In-Depth Information
in the major growing area of Wahiawa, Hawaii is 1850 mm per year (5 mm
per day). Even if annual rainfall closely approximates the optimal range, poor
distribution can result in periods of serious drought. In Loma Bonita and
Acayucan (Mexico) 89% and 82% of the rainfall, respectively, occurs between
June and November.
Despite the xerophytic characteristics of pineapple, growth is adversely
af ected by prolonged dry periods. Plants may not attain the desirable size
by the scheduled time for chemical fl ower induction. However, most areas of
the world where pineapple is cultivated have fairly high humidity, which can
reduce the impact of drought. At higher elevations, night air is cooled enough
to produce heavy dew, which condenses on the leaves and drains into the
heart of the plant and into the soil, providing supplemental moisture that can
be absorbed by roots in the leaf axils.
Temperature
In the absence of drought, temperature is the most important factor in
pineapple cultivation. The prevailing temperature determines the rate of plant
and fruit growth and, in conjunction with solar radiation, has a dramatic
infl uence on fruit total soluble solids and acidity, which are the primary
determinants of fruit quality. Under controlled conditions, the rate of root
growth at 18°C was less than 15% of the maximum, while the optimum
temperature was 29°C (Fig. 12.2). Leaf growth responds to temperature
in a manner similar to that of the roots, but growth is closer to 20% of the
maximum at 18°C and the optimum temperature is 32°C (Sanford, 1962).
Photosynthesis and plant growth approach a maximum when the day
temperature is near 30°C and there is about a 10°C diurnal range between
day and night temperatures (Malézieux
et al.
, 2003).
Warm days and cool nights provide the optimum environment for net
assimilation and growth. Growth is slow at an average temperature of 20°C
and at night temperatures below 15°C. In the cool season or in the cooler,
higher elevations, growth is delayed; leaves are upright, rigid and shorter;
the number of slips is higher; fruit may be smaller with prominent eyes; the
fl esh is opaque, higher in acidity and sugars are lower (Bartholomew
et al.
,
2003). However, the ef ects of seasonally cool temperature are confounded
with insolation, because irradiance decreases with the temperature during the
winter months.
Pineapple does not tolerate frost, and even night temperatures of 7-l0°C
for a few h for several weeks during winter can result in leaf-tip necrosis. Such
low temperatures can also cause fruit injury. A range of desirable minimum
night temperatures would be 15-20
°
C, while a comparable day temperature
range would be 25-32°C. The interaction of solar radiation and temperature
signifi cantly af ects the days from forcing to harvest. Further away from the
equator the amplitude of the temperature dif erence between seasons increases
and number of days from planting to harvest also increases.
