different maturation time of androecium and gynoecium in the same flower is
Plant reproductive morphology The primary mechanism used by flowering plants to ensure outcrossing involves a genetic mechanism known as self-incompatibility. Various aspects of floral morphology promote allogamy. In plants with bisexual flowers, the anthers and carpels may mature at different times, plants being protandrous (with the anthers maturing first) or protogynous (with the carpels mature first).[citation needed] Monoecious species, with unisexual flowers on the same plant, may produce male and female flowers at different times.[citation needed]
Papilionaceous flower The flowers have a bilateral symmetry with the corolla consisting of five petals. A single, large, upper petal is known as the banner (also vexillum or standard petal). The semi-cylindrical base of the banner embraces and compresses two equal and smaller lateral wings (or alae). The wings in turn enclose a pair of small keel petals, that are situated somewhat lower than the wings, but are interior to them.[1] They have concave sides and correspond with the shape of the wings. The two keel petals are fused at their bases[3] or stuck together[4] to form a boat-shaped structure that encloses the essential flower organs,[5] namely the androecium and gynoecium. Typically these flowers have a vexillary (i.e. descendingly imbricate or overlapping) aestivation.[3]