Seed Dispersal And Germination Characteristics Of Crocus Alatavicus (Iridaceae), A Gcocarpic Species

Crocus alatavicus, a geophytic-geocarpic species, is a perennial early-spring ephemeral that grows insubalpine areas of the western Tianshan Mountains. In China, the species occurs only in Xinjiang UyghurAutonomous Region (northwest China) and is found in the Yili valley in subalpine grasslands and forestedges. It is an early spring flowering geophyte that develops leaves and flowering shoots from buds on aperennial corm. The inferior ovary is belowground at anthesis, while the other floral parts are aboveground.Seeds have an elaiosome and are myrmecochorous. The primary aim of this study was to exploredevelopment of the underground ovaries and young fruits, seed dispersal, and the dormancy/germinationcharacteristics of seeds of this species. The main results are as follows:(1) Developmental time from flowering to emergence of the underground capsules above the soil wasabout35d. Thus, in C. alatavicus the fertilized ovaries and young fruits are protected from above-groundherbivores and damage by natural fires. Emergence of the underground capsules results from elongation ofthe peduncles, and then capsules dehisce and seeds are dispersed. Seeds of C. alatavicus have an elaiosome,which is typical of myrmecochores. Three ant species, Formica pressilabris, F. gagates and F. fusca, wererecorded near newly-dispersed seeds of C. alatavicus. The visiting frequency of F. pressilabris was thehighest, but F. fusca removed seeds faster and to a greater distance than the other two species. The averagedispersal distance of the three ant species was62.4±1.7cm. F. pressilabris, the major ant species takingseeds, ate the elaiosome after it moved the seeds into its nest and then stored more than50%of thetransported carried seeds in the nest. Thus, ants make a significant contribution to the dispersal of C.alatavicus seeds. Rodents and birds had no effect on seed dispersal of C. alatavicus, but hydrophily andanemophily played a minor role in short-distance dispersal.(2) In the natural habitat, the underdeveloped embryo in C. alatavicus seeds grows in early summer,and radicles emerge in early autumn. However, epicotyl emergence is delayed until the next spring. Radicle emergence was promoted by warm stratification and cotyledon emergence by cold stratification.GA3was ineffective in breaking either radicle or epicotyl dormancy. This is the first detailed study on theecophysiology of seed dormancy and germination in the genus Crocus.Ants make a significant contribution to the dispersal of C. alatavicus seeds. Formation of seedsunderground and their dispersal by ants help ensure that seeds escape damage from herbivores and fire andthat they are dispersed in a manner that reduces sib-competition and competition between mother plant andoffspring, thereby ensuring that seed germination and seedling establishment occur in a suitableenvironment. In the natural subalpine habitat, embryos grow during summer, radicles emerge whentemperatures start decreasing in the autumn, and the cotyledons did not emerge until the next spring. Weconclude that seeds of C. alatavicus have deep simple epicotyl morphophysiological dormancy. Theecological consequence of deep simple epicotyl MPD in seeds is that by emerging in spring seedlings canavoid exposure to severe winter environments. This pattern of dormancy is an adaptation to the seasonalcycle in temperate region.