Abstract
The presence of extrafloral nectaries (EFNs) between leaflets is an
usual feature in Inga edulis (Vell.) Mart. (Leguminosae). Extrafloral
nectaries are secretory structures involved in production of nectar and
which serve in the protection of plants against herbivores through
association with ants. This study aimed to characterize the EFNs of I.
edulis at different developmental stages and describe their morphology,
histochemistry and ultrastructure. Leaf fragments, containing secretory
structures, were processed according to standard methods for light,
scanning and transmission electron microscopy. The EFNs were classified
into three stages based on morphology: pre-secretory, secretory and
post-secretory. The pre-secretory stage occurs in young leaves, whereas
secretory and post-secretory stages occur in developed and senescent
leaves, respectively. The EFNs possess a concave surface and a central
cleft in which nectar is accumulated and which was not observed in
pre-secretory EFNs. Histochemical tests identified the presence of
sugars, proteins, phenolic compounds, mucilage and lipids at all
developmental stages of the EFNs. Calcium crystals were identified in
all tissues and stages of the EFNs. The secretory cells of the EFNs
exhibit a granular cytoplasm, small vacuoles, prominent nuclei, smooth
endoplasmic reticulum and mitochondria. Post-secretory stage EFNs
exhibited intense cytoplasmic degradation and the presence of
microorganisms. The performance of EFNs of I. edulis appear to follow
the leaf development.
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