Nectary structure of Labiatae in relation to their nectar secretion and characteristics in a Mediterranean shrub community - Does flowering time matter?

We studied the interrelation between nectary structure (13 parameters), nec tar characteristics (yield, chemical composition), and flower size of 11 La biatae species in a Mediterranean shrub community near Athens, Greece. We a lso explored whether the above attributes are affected by the Mediterranean summer drought constraints. Our findings show that among all nectary param eters studied, nectary size and stomatal opening are the most important in (positively) shaping nectar secretion, nectary size being the most meaningf ul. Nectary structure is correlated to quantity of the nectar secreted, not its quality. Wide Rowers bear wide nectaries with large stomatal openings, whereas deep flowers are not related to any nectary size. Corolla size (bo th length and width) and nectary stomatal opening decrease with flowering t ime. This applies also to nectary size, nectar volume and sugar content of the perennials (9 species). Ail above cases of time dependence show that th ere is a constraint effect of Mediterranean climate on floral and nectary s tructure, reflected also as a decrease in nectar secretion. Nectary structu re in Labiatae is largely shaped by both phylogenetic and climate constrain ts. On the other hand, although nectar is largely influenced by nectary str ucture, it is to a large extent ecologically biased, implying that, in addi tion to phylogeny, there are many other ecological parameters interfering i n its secretion such as time within the season, life history, and light req uirements.