MORPHOLOGICAL, HISTOLOGICAL AND CHEMICAL INVESTIGATIONS OF Tagetes patula L. | ||||
| Journal of Plant Production | ||||
| Article 9, Volume 25, Issue 8, August 2000, Page 5051-5076 PDF (878.53 K) | ||||
| Document Type: Original Article | ||||
| DOI: 10.21608/jpp.2000.259552 | ||||
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| Authors | ||||
| K. F. El-Sahhar,; L. A. Badr; R. K. Harb; H. A. Abd Al-Mageed | ||||
| Department of Agricultural Botany, Faculty of Agriculture, Cairo University, Giza, Egypt. | ||||
| Abstract | ||||
| Available botanical information on species of Asteraceae is little . Hence, this study aimed to present detailed information about the morphology ,histology and composition of the volatile oil of Tagetes patula L. throughout consecutive stages of plant growth in two years. Data obtained could be summarized as follows : Seeds of French marigold are disperesed in form of achene fruits, oblong 9 mm long and 1 mm width having a persistent calyx . Germination is epigeal with percentage of 36.75% .The seedling stage came to an end after 3-4 wks of sowing . The apex of the main stem differentiated into an inflorescence. Lateral branches (4-5) were responsible of the majority of shoot growth. Stem and lateral branches were erect, glabrous, more or less hairy, solid and greenish purple in colour . The main stem length reached 15 cm. Lateral branches are responsible of the actual height of plant, 45 cm.The average number of internodes of the main stem was 7 and the average diameter of basal internode was 12 mm. The dry weight of leafless shoot gained no considerable increments upto 14 wks old . At the following ages significant increments in the dry weight were achieved till the end of the growing season . The first foliage leaf develops 3 wks after sowing. Leaves are compound, opposite, decussate and imparipinnate . The active period in growth as indicated by dry weight of leaves occurred from 16 to 22 wks old. Flowering starts when plants aged 10 weeks. Both reproductive and vegetative growth continued parallel to each other till the end of the growing season. Lateral branches played a main role in flowering. The inflorescence is a capitulum developing at terminals of main stem and lateral branches and consists of ray and disc flowers arranged on a receptacle which is surrounded by an involucre arranged in one series .As to colour , ray flowers are golden yellow with red marking . Disc flowers are yellow with red colour at terminal of its internal surface. Seeds are produced in both ray and disc flowers.Number of consecutive pickings of inflorescences carried out fortnightly was 8-9 .The highest yield of inflorescences was obtained at the seventh picking .Fruit is ebony in colour with creamy persistent calyx atop the fruit , 1-5 hairs . Its base is also creamy in colour . From histological point of view, the main root is comprised of an epidermal layer followed by a cortex of 4-10 layers of cells ending with the endodermis . The pericycle surrounds a diarch vascular cylinder. The xylem occupies the centre and the phloem parenchyma cells have relatively thick walls. At the following ages these cells serve as supporting fibres .The secondary growth starts after 4 wks, and continued in the common manner. The shoot apex has 2- layered tunica surrounding the corpus. The xylem is the first vascular tissue to differentiate followed by the phloem, The stem directly below the apex is more or less pentagonal.The median internode of the main stem at flowering onset consists of an epidermis and cortex of 6-9 layers of cells. The first 2-3 layers of it are collenchymatous . The fascicular cambium forms more secondary xylem and less secondary phloem . The interfascicular cambium forms lignified parenchyma to the inside and thin walled parenchyma to the outside. The leaflet has 2 epidermal surfaces . The upper epidermis is concave in shape, while the lower one is convex. Stomata are of anomocytic type.The palisade layer is formed of 1 row of slender loosely arranged cells .The spongy tissue is consisted of 4-5 layers of chlorenchymatous cells , occupying 1/2 the whole thickness of the mesophyll. The midrib bundle has relatively narrow phloem, and a wider xylem area. The number of xylem rows in the midrib is 5-7 each of 3-5 vessels. The histology of ray and disc flowers was investigated. Also the fruit, the exocarp is consisted of epidermis and subepidermis . Some of the epidermal cells differentiate into a trichome of twinned hairs in addition to other glandular trichomes . The mesocarp is consisted of 2 layers which are palisade- like cells. The upper layer has cells which are more lignified than the lower one. The endocarp is consisted of 1-2 layers of thin- walled cells and prominent intercellular spaces. The seed coat is consisted of more or less spongy parenchymatous tissue . The inflorescences and the shoot produced volatile oil reaching 0.5%. The volatile oil of the inflorescences comprised of 31 components , tagetone being the main component . The volatile oil of the shoot comprised of 33 components with γ - terpinene as the main component . | ||||
| Keywords | ||||
| Tagetes patula L; morphology; histology; volatile oil | ||||
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