Ds. Achor et al., ANATOMICAL AND HISTOCHEMICAL EFFECTS OF FEEDING BY CITRUS LEAFMINER LARVAE (PHYLLOCNISTIS-CITRELLA STAINTON) IN CITRUS LEAVES, Journal of the American Society for Horticultural Science, 122(6), 1997, pp. 829-836
Young expanding leaves of 'Ambersweet' [Citrus reticulata Blanco x C.
paradisi Macf. x C. reticulato.) x C. sinensis (L) Osb.] with feeding
injury by third larval stage of citrus leafminer (Phyllocnistis citrel
la) were examined by light and electron microscopy for extent of injur
y and tissue recovery over time. Results confirmed that injury is conf
ined to the epidermal layer, leaving a thin covering over the mine tun
nel that consisted of the cuticle and outer cell wall. Wound recovery
consisted of two possible responses: the production of callus tissue o
r the formation of wound periderm. The production of callus tissue dev
eloped within 3 days of injury when the uninjured palisade or spongy p
arenchyma below the injured epidermis produced callus tissue through p
ericlinal or diagonal cell divisions. After 1 month, the entire epider
mis was replaced by callus tissue. In the absence of secondary microbi
al invasion, this callus tissue developed a thick cuticle, followed by
development of a covering of platelet wax after 4 months. Alternative
ly, wound periderm formed if the outer cuticular covering was torn bef
ore the cuticle had developed sufficiently to prevent the exposed cell
s from being desiccated or invaded by fungi, bacteria, or other insect
s. The wound periderm consisted of a lignified layer of collapsed call
us cells, a suberized phellem layer, and a multilayered phelloderm-phe
llogen. Since there were always cellular collapse or fungi and bacteri
a associated with wound periderm formation, it was determined to be a
secondary effect, not a direct effect of leafminer feeding.