Ultrastructural study on apricot floral nectary

Abstract：In order to understand the ultrastructural characteristics of mature floral nectaries of apricot,nectaries in flower buds that just begin to expose corolla were studied using light and electron microscopy.The significant findings include：（1） the nectary epidermal surface was specialized to form ridge-like protrusions and,concomitantly,to form deep holes and shallow pits between the ridges.This ridged pattern was consistent with cell wall protrusion pattern.（2） Plastids in nectary parenchyma cells were differentiated into chromoplasts,where plastoglobuli were accumulated at first,and then plastoglobuli were changed into crystals.It was supposed that the storage accumulation was mainly composed of lipid and carotenoids at first,but dominantly included proteins and carotenoids later.（3） The nectary parenchyma cells contained well developed mitochondria and rich endoplasmic reticula,indicating highly active energy transduction and active secretory protein synthesis.This was the characteristic of secretory cells.Therefore,the floral nectary in apricot was characterized by the presence of chromoplasts,the conversion of plastoglobuli to crystals,the existence of rich mitochondria and endoplasmic reticula,and the formation of ridged surface of the sectary tissue.