Fig. 1. SEM (A-D,I,K and O) and sections (E-H,J,L-N and P) of nectary development. (A) Arabidopsis flower before anthesis, stage 12-13 highlighting nectary glands (arrows). (B) Higher magnification of A showing lateral and medial nectary glands with intervening ridge (r) of tissue (arrow). (C) Close-up of lateral nectary gland showing reticulate pattern of the cuticle and modified stomata. (D) Close-up of medial nectary gland and intervening medial region without characteristic nectary gland cuticle. (E) Transverse section of two medial nectary glands and intervening region (arrow). (F,G) Transverse and longitudinal section of a lateral nectary gland, respectively. Arrows indicate sieve tube members (stm) and arrowheads indicate guard cells (gc). In G the nectary gland is expressing CRC::GUS. In E and F starch appears as dark grains within the cells of the nectary gland and intervening region. (H) Transverse section of the flower receptacle of a stage 9 flower. Arrows point to newly formed periclinal divisions of the L2 layer. (I) Morphology of a young lateral nectary gland from a stage 10 flower. (J) Transverse section of a stage 9-10 flower receptacle showing the early developmental anatomy of a lateral nectary gland. The gland is composed of two small protrusions from the receptacle. (K) Close-up of a medial and lateral nectary gland with intervening ridge of tissue (arrows) from a stage 13 flower. (L,M) Two serial consecutive sections of a stage 7/8 flower showing CRC expression. There is no expression in the medial domain in the region between the two medial stamens. (N) Transverse section of two medial nectary glands taken just within the receptacle of a stage 12 flower. Receptacle tissue is present in between the two glands and is expressing CRC::GUS (arrow). (O) A stage 13 crc mutant flower. The nectary glands are absent. (P) Transverse section through a stage 13 flower receptacle of a crc-1mutant showing three cell layers expressing CRC::GUS (red crystals), there is no expression in the middle of the medial domain. ln, lateral nectary gland; mn, medial nectary gland; lst, lateral stamen; mst, medial stamen; l, lateral domain; m, medial domain; pe, petal. Scale bars, 100 µm for A,B,D-H,K,N and O; 50 µm for I and J; 20 µm for C.