In the case of the plot containing the “Fino 49” trees grafted on
Sour orange, the irrigation treatment of 40% under a screen produced
fruits having a yellow-green coloration, not reaching the
characteristic intense yellow of lemons (Fig. 3, Table 1). The trees in
this treatment (under the screen, 40% ETc) were the only ones that
reached a leaf water potential at noon below
−2.5 MPa (Table 2).
In the case of the trees in the open, the leaf water potential did
not decrease below
−2.2 MPa in the drought treatments, while the
trees with the mulch had values above
−2.0 MPa. This suggests that
the water status of the plant is an important factor to take into
account in the natural process of de-greening of lemon fruits. In this
sense, Kallsen and Sanden (2011) observed, in Navel orange trees,
that drought treatments severely diminished the color of the fruit’s
skin at the end of November, retarding their natural de-greening.
Navarro et al. (2013), in research performed on Clemenule mandarins,
observed that the season in which irrigation is stopped can
differently affect the change in color of the fruits. Therefore, when
drought was applied from June to October the fruits had a lesser
coloration that when the period of drought was during October
and November. As for mulching, in other experiments we found
that a reduction of the soil temperature, produced by covering the
soil during the two months previous to harvesting through the use
of a white reflective plastic, brought forward the change of color
of the skin of Clementina (Clemenpons) fruit, allowing earlier harvesting
(Mesejo et al., 2012). However, we hardly saw an effect on
the change of the color in our current experiments.