Agriculture Reference
In-Depth Information
(
2001
) suggested that there is an improvement of taste and flavor of tomato fruits
by increasing the salinity, and applying the right humidity management program to
the shoot environment. Lowering the transpiration rate can modify the effect of the
root zone salinity, both by reducing the proportion of nonmarketable fruits, e.g. by
the incidence of blossom end rot and reducing the decline in fresh weight. In gen-
eral, manipulating the indoor climate, such as humidity, temperature and ambient
CO
2
level, may offset the negative effect of high salinity on yield and fruit quality
such as BER (Stanghellini et al.
1998
; Dorais et al.
2001
). These results were con-
firmed by Romero-Aranda et al. (
2002
) where greenhouse misting increased instan-
taneously improved the WUE of tomato yield and fruit size regardless of salinity.
On the other hand, low VPD can cause other disorders, such as, cracking and rus-
seting (fine hairline cracks) of tomato and bell pepper fruits. According to Demers
et al. (
2007
), a hypothesis could be drawn that low VPD decreases leaf transpiration
but increases root pressure, which in turn increases fruit water supply and turgor
pressure. Under such conditions, a greater stress would be applied to the fruit skin
and cuticle, which would increase the likelihood of the development of cuticular
and fruit cracking. Although, in this study, no significant effect of day/night RH
regimes on fruit russeting was observed, it is reasonable to presume that the effect
of high RH on russeting would be more pronounced if the high rH occurred at night,
when leaf transpiration is already reduced.
By contrast with light and temperature, data concerning the influence of air hu-
midity on internal greenhouse vegetable quality are generally scarce except for to-
mato fruits (Gruda
2005
). Bertin et al. (
2000
) and Guichard et al. (
2001
) reported
that, the dry matter and sugar concentrations of fruit exposed during their growth
to high VPD was higher than those of fruit exposed to low VPD, apparently due
to a decrease in water accumulation by the fruit which led to a 30 % reduction in
the net accumulation of water by the fruit (Guichard et al.
1999
). Investigations
by Mortensen and Fjeld (
1998
) with potted roses demonstrated that increasing air
humidity reduced the vase life of roses from 8-13 to 2-5 days and caused the early
onset of leaf drying and “bent neck” during the stage of shoot growth. According
to Torre and Fjeld (
2001
) and Mortensen and Gislerod (
2005
) air relative humidity
of 85-90 % during active growth is a critical environmental factor that reduces the
postharvest life of cut roses, mainly due to uncontrolled water loss from the cut
shoot. Torre et al. (
2003
) reported that roses subjected to high RH showed differ-
ences in leaf anatomy; stomatal morphology and stomatal function, may explain
the loss of water control from these plants. The authors concluded that stomatal
ontogenesis should occur at RH conditions below 85 % to secure roses with a high
postharvest quality potential.
