Environmental Control of Garlic Growth and Florogenesis

An understanding of temperature and photoperiod effect on garlic (A. sativum L.) growth and florogenesis might solve the enigma of garlic sterility and provide environmental tools for flowering regulation and fertility restoration. The effect of storage temperature and growth conditions on the interactive relationships between the developing vegetative and reproductive organs was studied. A long photoperiod for more than 2 weeks was required for both dormancy induction of the axillary buds and clove formation. In contrast, combination of low temperatures with short photoperiod resulted in sprouting of the axillary buds. Four phases were recognized in the florogenesis of garlic, including: transition of the apical meristem, scape elongation, inflorescence differentiation, and completion of floral development. In garlic accession #2091, meristem transition is autonomous and occurs in growing plants under a variety of storage and growth conditions. A long photoperiod triggers the initial elongation of the scape in post-transitional plants. The temperature effect was quantitative: low storage and growth temperatures combined with long photoperiod promoted scape elongation, whereas warm temperatures and long photoperiod promoted the translocation of reserves to the cloves, and the degeneration of the developing inflorescence. Differentiation of topsets followed flower formation and was dominated by and required lengthy exposure to long photoperiod. Hence, under short photoperiod with only short interruption of long photoperiod, normal development of fertile flowers occurred. We conclude that in bolting garlic genotypes, manipulation of the environment, both before and after planting, can regulate the development of flowers and regain fertility. Normal flowering cannot be achieved if any of the four developmental stages of florogenesis mentioned above is inhibited.