Flower disk flowers

Palea One of the chaffy scales on the receptacle subtending the disk flowers in many composite plants or the upper bract, which, with the lemma, encloses the flower in grasses. 

The stem is erect, columnar at the base and branched at the top. The leaves are alternate, simple, rough, hairy, and ovate or heart-shaped with toothed edges. The heads are showy, with yellow to orange-yellow ray flowers and brown or dark reddish-brown disk flowers. Sunflowers begin to grow in early June, flower in August and September, and mature seed and die in late September. 

Flower heads occur alone or in groups at the ends of the stem and axillary branches. Each inflorescence is comprised of many small, yellow, tubular disk flowers in the center, surrounded by 10 to 20 sterile, yellow ray flowers, the ligules of which are often thought of as the petals (Figure 4.3). 

The number of disk flowers varies among clones and with position on the plant. In a representative clone, there was an average of 58.8 disk flowers per inflorescence, with the inflorescences ranging from 4 to 8.5 cm in diameter. The diameter was slightly larger on flowering branches than on the main stem. 

Fig. 235.-—Capitulum o a composite Jerusalem artichoke Helianlhus tuberosus). A, lengthwise section of capitulum, X i B. ray flower, X 6 C, disk flower, cut lengthwise, X 6. (A after Baillon, B and C, Robbins.)...

Dual choice tests with 8 pi of solvent or compound per 1.5 cm flower disk = significantly different from methanol control at p < 0.05 based on area consumed. 

Description Herbaceous annual or biennial, 30-90 cm tall, covered with long, white, raised hairs. Stems single or multiple, erect, branched. Lower stem leaves petiolate, tripartite-pinnatisect, 3-7 cm long cauUne leaves sessile, tripartite. Inflorescences 3-5-flowered capitula in panicles. Disk flowers yellow, punctate glandular ray flowers absent. Fruits obo-vate achenes, 2-2.25 mm long, olive-colored. 

Figure 3.23. Schematic and micrograph of spreading, breakup and solidification modes of liquid metal droplets impinging on a cold surface. (a)-(d) Pancake pattern regularly shaped disks with or without corona, (e)-(h) Flower pattern irregularly shaped platelets with or without corona. (Micrograph reprinted with permission from Ref. 403 and 407. Courtesy of Dr. J. M. Houben, Eindhoven University of Technology, Netherlands and courtesy of Dr. Seiji Kuroda, National Research Institute for Metals, Japan.)...

Petals usually absent, if present either choripetalous or sympetalous ovary unilocular mostly parasitic shrubs or herbs.Order Santalales 4 Flowers typically sympetalous, the choripetalous groups mostly with umbels epigynous hypanthium rare calyx often reduced or replaced by a specialized pappus frequently flowers in disks or heads. 

Disk In composites, the central portion of the head composed of the tubular flowers in many other species of flowering plants an enlargement of the receptacle around the pistil or androecium. 

Horseweed is a native annual plant that can grow to a height of over 2 m. When mature, several flowering stems appear at the apex, which branch frequently and create a multitude of tiny composite flowers. In each flower, there are numerous yellow disk florets in the center, which are surrounded by tiny white ray florets. There is no noticeable floral scent. The blooming period can occur any time from midsummer to fall, lasting about 3 wk. 

In the Compositae family are herbs such as Lads Love, Marigold, Mugwort, Tansy, Tarragon, Wormwood, etc., and these herbs have flowers which are ray or disk shaped, for example daisies, dandelions. 

Figure 11.4. Typical inclined extinction directions in columnar flower-like domains between horizontal and vertical crossed polarizers and its interpretation assuming tilted disks in curled columns extinction occurs in diagonal directions where the disks are parallel to a polarizer. (Reprinted with permission from Ferroelectrics 179, 203 1996, Gordon and Breach [6].)...

Acaricidal and insecticidal activities of the synthesized compounds were determined as follows. In the case of two-spotted spider mite (T. urticae), female adult mites were placed on the excised leaf of kidney bean seedling, and then, the test solution (test confounds were dissolved in acetone at 20 to 200 ppm) was sprayed onto die leaf. Mortality was determined 2 days after the treatment. In the case of western flower thrips (F. occidentalis), first instar larvae were released on released on the excised leaf of kidney bean seedling (15 larvae per a disk), which was then sprayed with the test solutioa Mortality was determined 2 days after the treatment. In die case of silver leaf Miitefly B. argentifolii), adult whiteflies were released on die cabbage leaf and allowed to oviposit for 24 hours. Adults were removed from the leaf and the leaf was stood for 7 days. A leaf disk of 20 millimeters in diameter was excised from the leaf and sprayed with the test solution. Mortality was determined 6 days after the treatment. The acaricidal and insecticidal activities were indicated as activity indexes 3,2 and 1 which represent the mortality of 100%, 99% to 50% and less dian 49%, respectively. 

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