Environmental Control of Garlic Growth and Florogenesis

Abstract

<jats:p>An understanding of temperature and photoperiod effect on garlic (<jats:italic>A. sativum</jats:italic> 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.</jats:p>

Phospholipase D from Allium sativum bulbs: A highly active and thermal stable enzyme

“…Similar results have been observed in the case of a recombinant thermostable glutamate dehydrogenase (GDH) from a hyperthermophilic archaeon which was activated 2.6-fold upon heat treatment, i.e. 80 • C for 15 min [25]. It was observed that the heat treatment resulted in a reduction of the helical content of GDH along with the increase in the specific activity.…”

Effect of Low Storage Temperature on Some of the Flavour Precursors in Garlic (Allium Sativum)

“…The storage environment is a micro-climate which can further affect the composition of the bulb and cloves. While low temperatures promote the breaking of dormancy in garlic [11,16], garlic cultivars stored at 0 • C and 25 • C for eight weeks showed no significant differences in production of allicin, a breakdown product of alliin [17]. Cantwell et al [18], however, identified an increase in alliin, thiosulfinate and total pyruvate, all measures of flavour sources, in garlic stored at 0-1 • C for up to 4 months.…”

New phenological growth stages of garlic (Allium sativum)

“…During its domestication process, garlic began to lose its capacity to sexually reproduce, and seeds are not produced in the majority of current cultivars (Al‐Zahim et al , ; Volk et al , ). Viable seeds are only produced by some varieties from near of Centre of Origin (Hong & Etoh, ; Shemesh et al , ) and under specific environmental conditions (Kamenetsky et al , ; Shemesh et al , ). The current means of garlic propagation is vegetative, from cloves of harvested bulbs (Messiaen et al , ).…”

“…In addition, not all cultivars completely develop an inflorescence, as many intermediate forms exist (in hard‐neck cultivars), or the apical bud may be substituted by a central clove (in soft‐neck cultivars). Although this is a genetic characteristic frequently used to classify plant material, distinct environmental conditions may noticeably modify the expression of a single cultivar (Kamenetsky et al , ). With regards to the formation and development of an inflorescence, Takagi () and Kamenetsky & Rabinowitch () claim that garlic types can be classified as one of the following: complete bolting, non‐bolting and incomplete bolting.…”