Reproductive biology of Saffron flower
The origin of saffron is still an open question to the science world. In this article, the Saffron Express team is trying to briefly explain the sexual reproduction of the saffron plant, which is a very interesting process. Continue reading in below:
Many studies have been dedicated to the biology of saffron flower reproduction. Due to its triploid, saffron flower is usually multiplied through selected corms. This process is carried out by man. Only rarely have seeds in Crocus sativus been reported in nature, despite the abundant production of sexual reproductive structures such as pollen and ovules.
The life cycle of the Plant
This plant has a life cycle characterized by a long summer break and vegetative activity from autumn to spring. The plant, after the loss of leaves, survives the summer as an underground corm. During this period the corm prepares the buds that will originate the new leaves and flowers. The
leaves sprout from apical buds on a short stem and are embedded by whitish bracts. Other apical buds originate from the flowers, which are frequently hysteretic or appear just after the leaves do. At the base of mother corms, smaller new corms also occur, creating a new saffron flower which normally produces only leaves. The number of new leaves, flowers, and daughter corms depend on the dimensions and age of the mother corms, on cultivation methods, and environmental conditions. The number and quality of buds originating leaves, flowers or young corms depend on the number of resources that the mother corm can accumulate during the vegetative period. Recent research considers it as a bulk of clones accumulated during the millennial cultivation of the plant by man. The selection of the bigger corms is proposed as a system for improving its cultivating.
Although the selection of the bigger corms is a common practice carried out by the farmers over many countries, a clonal selection of corms with high yield capacity is a program with great potential. The corm after some years of cultivation in the same field does not produce saffron flowers. The number of saffron flowers depends on various factors including the age of the corms. Such considerations date back to the law according to which, in a plant, the allocation of resources between vegetative and reproductive phase are correlated. If the plant uses more resources in producing flowers, in the following years it will have fewer resources for vegetative production such as corm, stem, leaves, flowers, and fruits. More recently, scientists described the bulbils versus seed production in the Liliaceae Gagea. These observations shed light on the very difficult conditions that saffron has to overcome in surviving as a wild plant in the natural state. Observations on corms left in the field for 10 years without cultivation practices demonstrated that the corms decreased their dimensions and flower production over the years. The smaller corms had only one leaf, whilst larger corms had 2-8 leaves. Thus, after ten years without cultural intervention, the corm loses its vigor and degenerates, giving rise to smaller corms unable to flower and produce new corms. As far back as a research in 1847, hypothesized that wild saffron flower disappeared as a consequence of changes occurring in its natural habitat.
Read also: The soil impact on saffron cultivation
The triploid condition of the product causes an anomalous pairing of the chromosomes at the prophase of meiosis, and irregular distribution of chromosomes at metaphase with a consequent infertile gametes production. The Saffron Express team informs you that however, often in the triploids, pollen and ovules do not exhibit the same behavior. Generally, infertility in uneven polyploids is much higher in the pollen when compared to the ovules. This aspect has been studied in saffron and compared to the behavior of the allied diploid species by focusing on the structural organization of the reproductive structure as well as on the process of compatibility and incompatibility among species of the Crocus group.
The data obtained to date by Saffron Express from archeology, systematic, cytology, molecular biology, physiology, and biochemistry are still insufficient to establish a precise place and moment for the origin of this herb or its parents. However, the information accumulated in recent years offers further indications about the probability that one of the diploid Crocus is the parent of C. sativus. All data agree that the most probable parent of saffron is C. cartwrightianus, only if the origin of saffron is considered by auto replied or together with C. thomasii, if the origin is due to allotriploid. In fact:
- remote archeologist and historical records suggest that a Crocus has been known and widely used since preHellenistic and Hellenistic times. All authors agree on considering cartwrightianus as the crocus used in therapy and other fields; wild and cultivated forms are already known;
- saffron grown and used today corresponds to sativus which morphologically is very similar to C. thomasii with which it has been confused in the past;
- reproductive biology makes it possible to ascertain that saffron is self- and allow sterile, although its ovules can be fertilized by the pollen of cartwrightianus as well of C. thomasii. The crossing leads to seed set and fruits;
- seeds from crossing saffron with cartwrightianus are viable and capable of germinating, giving rise to a seedling and then a plant from which new corms originate. The germination and growth behavior of the seeds are very similar to that of C. cartwrightianus;
- the chromoplast structure and pigment composition place saffron very close to thomasii and C. cartwrightianus;
- although the path of origin of saffron flower is still an open question, important new contributions could be reached by new research methods on chromosome structure and molecular genetics. The need now is to research its biological aspects, mainly on crossing with the diploid allied species and then examined the progenies with improved molecular methods. It will be a very long way but we think that a young research team could meet this goal and reach interesting results to solve the puzzle of parents of this product. The results could be useful to obtain the genetic amelioration of the cultivated saffron flower.
Saffron Express also invites you to read our previous articles about Historical Background of saffron use in arts and literature and to learn more about its stunning historical background and also read our article on Botanical Qualities to know more about this plant’s characteristics.
Agayev YM, Fernández J-A, Zarifi E (2009) Clonal selection of saffron (Crocus sativus L.): the first optimistic experimental results. Euphytica 169, 81-99
Chichiriccò G (1987) Megasporogenesis and development of embryo sac in Crocus sativus L. Caryologia 37, 233-239
Di Crecchio R (1960) Lo zafferano. L’Italia Agricola 97, 629-649
Grilli Caiola M, Canini Antonella (2010) Looking for Saffron’s (Crocus sativus L.) Parents. Functional Plant Science and Biotechnology 4 (Special issue 2). pp 7-8
Grilli Caiola M, Zanier R (2005) Self-incompatibility in different Crocus species and in Hermodactylus tuberosus (Iridaceae). Acta Biologica Cracoviensia. Series Botanica 4 (Suppl. 1), 57
Herbert W (1847) History of the species of Crocus. Journal of the Horticultural Society of London 2, 249-293 Piccioli G (1932) La coltura dello zafferano ne L’Aquila degli Abruzzi. Cellamare, L’Aquila, 178 pp
Schnittler M, Pfeiffer T, Harter D, Hamann A (2009) Bulbils contra seeds: reproductive investment in two species of Gagea (Liliaceae). Plant Systematics and Evolution 279, 29-40 Tammaro F (1987) Notizie storico colturali sullo zafferano (Crocus sativus L. Iridaceae) nell’area mediterranea. Micologia e Vegetazione Mediterranea 2, 44-59
Tammaro F (1990) Crocus sativus L. cv di Navelli (L’Aquila saffron): environment cultivation, morphometric characteristic, active principles, uses. In: Tammaro F, Marra L (Eds) Lo Zafferano, L’Aquila, Italy, pp 47-96