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Abstract
Datura gave the highest average in plant height (158.3 cm.) which was achieved at the age of 120 days followed by pepper plant (83.2 cm) at the age 150 days and potato plant was the lowest being 67.3 cm. when plants were 105 days.
The three genera Solanum tuberosum L. (potato), Capsicum annuum L. (pepper) and Datura stramonium L. (datura) gave nearly the same average in diameter of the third basal internode of the main stem, being 2.08, 2.16 and 2.28 cm., respectively.
As for the number of internodes per main stem, potato gave the highest average (16.2) followed by pepper (14.8) and datura (5.0) internodes. A reverse corresponding relation could be noticed between plant height and number of internodes, as datura was the highest in plant height (158.3 cm) and the lowest in internode number (5.0), followed by pepper plant (83.2 cm) in height and (14.8) internodes, potato plant ranked the lowest in plant height (67.3 cm) and the highest in internode number (16.2). It is also noticed that the number of internodes of the main stem in Solanum was 5.4 internodes at the age of 30 days. Thereafter continuous gradual increases in number were achieved during the following stages until the end of the growing season being 16.2 internodes. The same trend was observed in Capsicum, as the number of internodes recorded 8.3 internodes at the age of 30 days. This was followed by continuous gradual increases during the successive stages until the end of the growing season (150 days), being 14.8 internodes. A different trend was noticed in Datura regarding the number of internodes of the main stem, as the number reached 3.35 internodes at the age of 30 days, thereafter continuous gradual increase was present until the age of 75 days, being 5 internodes, and this number remained constant till the end of the growing season (120 days).
Datura recorded the highest average in fresh weight of leafless shoots / plant (681.4 g), than potato (83.2 g) and pepper (312.1 g). This matches with the plant height, as datura was the highest (158.3 cm) followed by pepper (83.2 cm.) and potato (67.3 cm). The same trend of the fresh weight was apparent in the results for the dry weight of leafless shoots / plant, that recorded the highest average in datura (81.8 g), followed by pepper (37.7 g) and potato (12.5 g). Concerning to the leaf characters, pepper gave the highest average in number of leaves / plant (802.4) followed by datura (410.6) and potato (127.4) leaves / plant.
Datura recorded the highest average in leaf area / plant (11941.5 cm²) compared with pepper (8227.6 cm²) and potato (3026.7 cm²). Although pepper plant was the highest in average number of leaves (802.4 leaves) and datura ranked the second in number (410.6 leaves/ plant), yet datura was the highest in leaf area/ plant (11941.50 cm²) followed by pepper plant (8227.6 cm²). This unexpected result could be due to the area of the individual leaf, and not to the leaf number alone. Potato plants ranked the third (the lowest) in both average number of leaves/ plant (127.4 leaves) and leaf area/ plant (3026.7 cm²). Datura showed the highest average in both fresh weight of leaves (391.6 g) and dry weight (52.7 g) / plant, followed by pepper, which gave (223.5 g) and (26.7 g) for fresh and dry weights, respectively. While potato recorded the lowest average in fresh weight of leaves / plant (128.7 g) and dry weight of leaves / plant (16.8 g). the weight of the dried leaves was almost the 8th of the fresh weight of leaves/ plant in the 3 studied genera. The same sequence of fresh and dry weights of leaves/ plant, applies also to that of fresh and dry weights of leafless shoot/ plant; as datura was the highest followed by pepper and the lowest was potato.
II. Anatomical studies:
For comparing the anatomical features of the three studied Solanaceae genera under investigation. Generally, the main essential differences could be summarized as follows:-
The root of Datura showed the narrowest root vascular cylinder followed by Solanum while, Capsicum produced the wider one. With regard to the vascular cylinder structure the three studied genera showed radial protostele, with different types of xylem poles. Since, Datura showed tri-arch xylem poles, while it was poly-arch in case of Capsicum as well Solanum which, maintained penta-arch and hexa-arch for Solanum and Capsicum, respectively. Roots 21 days old of the three studied genera exhibited dissimilar degrees of differentiation of the metaxylem vessels as well the phloem. where, Solanum showed a fairly differentiated metaxylem with wide vessels and well developed phloem. In case of Datura it was poorly differentiated with narrow metaxylem vessels. While, Capsicum showed intermediated degree of differentiation for both metaxylem and phloem.
The stem layout as shown in transverse section of Solanum was nearly rounded or may tend to be polygonal in outline shape, Datura was round in outline, while, it was quadrangular with four furrows and four ridges in case of Capsicum Spp. The three studied genera showed normal basic epidermal cells with thin waxy cuticle. The epidermis showed single normal uniform barrel epidermal cells in the three studied genera. Epidermal hairs and trichomes were detected on the outer surface of the stem. As Solanum showed two types of multicelular uniceriate and glandular hairs while, capsicum showed unicellular, multicellular hairs as well glandular hairs. No epidermal attachements were found on the epidermis of Datura stem. Moreover, the three studied genera exhibited one row of hypodermal parenchyma. The three studied genera showed a well developed cortex that mainly characterized by two main distinctive layers. The outer one compresses many rows approximately (5-7) of angular collenchyma. This region of collenchyma almost appear as stem sheath surrounded the inner parenchyma region of the cortex. The vascular bundles mainly characterized by wide internal phloem with scattered clusters of fiber cells. Xylem vessels as shown in the secondary xylem of the three studied genera showed variable sized vessels arranged in radial pattern with a uni-seriate to multi-seriate rays 1-8 cells wide which dissected between the vascular bundles. The pith was unflanged in the three studied genera with relatively wide thin walled parenchyma cells. The three studied genera showed variable pith in diameter. As Solanum showed the wider pith followed by Datura and Capsicum. The variation in pith diameter was achieved according the changes found in thickening of the vascular cylinder. The pith of Datura Stem in median internode show hallow pith cavity.
The leaf petiole of the three studied genera was semicircle outline shaped in potato while it was reniform in case of pepper and round like in shape in datura. The bicollateral vascular bundle seemed to be differed in its shape and size. Since, the central vascular bundle was crescent in out line shape in both Solanum and Capsicum, while it was u shaped in Datura. The three studied genera could be ranked in descending order according to the central vascular bundle size as, Solanum followed by Datura and Capsicum. The central vascular bundle was relatively wider and thicker than the other two bundles. The three studied genera showed differed in the thickness of the vascular bundle. Xylem was varied in vessels size and mainly oriented toward the abaxial side. The external phloem in general was wider and thicker than the internal phloem.
The leaf midrib region of the three studied genera was differed in size. Though Datura showed the largest midrib region followed by Solanum and the Capsicum, that showed the narrowest midrib. This may be due to the size and number of parenchyma cells, that found in this area as well the differences in the thickness of the vascular bundle. Since, Datura showed the largest midrib region that compressed an abundant amounts of relatively large parenchyma cells and thick vascular bundle. The pepper leaf paisade tissue was extended toward the midrib and showed under laying row just beneath the midrib upper epidermis. Moreover, the differences in measurements and counts of different tissues being recorded in this study may be expressed to nature of growth of each genus.
The stolon cortex showed multilayered wide polygonal parenchyma cells followed by vascular cylinder exhibited bicollateral vascular cylinder, where xylem elements oriented between the outer and inner phloem. It is evident that the outer phloem was relatively thicker than the inner. Xylem showed variable sized vessels that arranged in arrays and compressed wide meta xylem vessels and comparatively narrow proto xylem. The pith was relatively wide.
Potato tuber in transverse section showed semi-circle in shape. The phellum showed 12 rows of well developed subernized cork cells that arranged in vertical arrays with no intercellular spaces. The phellum was followed by phellogen which appear to be in active periclinal. Phelloderm was apparently mixed with the cortex and characterized by wide parenchyma cells. It is difficult to differentiate between the boundary of the outer medulla and the inner one.
Pepper fruit pericarp was bounded by relatively thick waxy cuticle. The fruit mesocarp could be divided into three main regions; hypodermal, central parenchyma and giant parenchyma region. The hypodermis compressed abundant amounts of parenchyma cells. The inner most region showed giant parenchyma cells that varied in size and may showed parenchyma bridges at the end of the mesocarp that composed of single row of parenchyma cells. The endocarp was slightly thin
Datura fruit pericarp showed cuticle bounded the whole fruit exocarp which exhibited multi layers of small thick walled fibrous cells. The fruit mesocarp showed two distinguish layers; the outer composed of circular sheath of fibrous cells (sclernchyma) that bounded the fruit mesocarp. The inner region composed of multi layered parenchyma cells. The fruit endocarp was slightly thin and composed of single cell row.