Helianthus
or sunflowe s is a
70 species in the family Asteraceae. Except for thr e species in South America, all Helianthus species are na ive to North America. The com on name, "sunflower," also a plies to the popular annual species Helianthus annuus, the c mmon sunflower. This and other species, notably Jerusale artichoke H. tuberosus , are cultivated in temperate regions as food crops and ornamental plants.
Sunflowers are usually tall a nuals, that grow to a height of 50–400 centimete s (20–157 in). The rough and hairy stem is branched in the upper part in wild plants but is us ally unbranched in domesticated cultivars. The petiolate leaves are . , ovate or often heart-shaped. They bear one or several to any wide, terminal capitula (flower heads), wit bright yellow ray florets at the outside and yellow or maroon (also known as a brown/red) disc florets insi e. Several ornamental cultivars have red-colored r y florets; all of them stem from a single original muta t. During growth, sunflowers tilt during the d y to face the sun, but stop once they begin blooming. his tracking of the sun in oung sunflower heads is called heliotropism. By the time the are mature sunfl wers enerall face east. Helianthus species are used as food plants by the larvae of many lepidopterans.
Scientific Classification Kingdom: Pla tae u ng om: Tracheobionta Superdivisio : Spermatophyta Division: Magnoliophyta •
•
•
•
Subclass: Ast ridae Order: Asterales Family: Aster ceae Genus: Helia thus
• • • •
The sunflower reproduces sex ally through the method of pollination. On one indivi ual flower, the sunflower contains both the female and ale sex or ans. On the disk of the sunflower, if looke at closely, one will be able to see a five pointed, fuse corolla. This is actually five petals commixed together to make a whole corolla. Found in the center of each co olla, are both the male and female reproductive orga s. The anther which contains the pollen, besets the style of the pistil. Then as the style progresses to grow, the pollen is propelled out. This is where the insects, llured by the petals, come find pollen. Once found by the insects, the pollen is picked up and moved to oth r sunflowers. Then when the style is completely done gr wing and the pollen is all gone, the style becomes dis losed and waits for pollen left from insects from a other flower.
The sweet pea is an annual flower grown in cool mariti e or mountain , all summer. They're est in cool seasons like winter a d early spring.
Sweet peas are vini g plants that climb vi orousl -- six to ei ht feet over fences and oth r supports. The flowers are pin , white, red, lavender, purple, and near blue
Scientific cl ssification Kingdom:
Plantae
(unranked): Angiosperms (unranked): Eudicots (unranked): Rosids Order:
Fabales
Family:
Fabaceae
Tribe:
Vicieae
Genus:
Lathyrus
Species:
L. odoratus
Materials Required:
, , dissecting microscope, slid s etc.
,
,
Sunfl wer Experimental Procedure:Take sunflower and cut it into two e ual halves b a longitudinal cut passing t rough the centre. Observe its florets carefully with the help of hand lens and under the microscope.
Observation: Sunflower is an inflorescen e called capitulum or head in which small, sessile flowers called florets are borne on a flattened rec ptacle in centripetal manner. The inflorescence s surrounded b one or more whorls of bracts cal ed involucre. In sunflower, the central florets are bisexual and tubular called disc florets w ile the peripheral florets are ligulate called ra florets. 1)Ray florets. These are pres nt in the periphery and have brightly coloured strap shaped petals. Stamens are absent and ova ies are without ovules. Ray florets act as or ans of attraction for insects. 2)Disc florets. These are pre ent in the central region of the inf lorescence. heir corolla consists of five fused petals forming tube. Stamens are five with fused anthers and ree filaments. This condition of stamens is call d syngenesious. The ovary consists of two fused arpels containing only one ovule. The style is long with two stigmas. The nectary lies at he rase of the style.
Pollination Mechanis Sunflower is protandrous i.e. the sta mens ripen before the stigmas. In the young disc florets, the anthers split along their inner sides, so that the pollen grains are shed into the tube formed by the joined anthers. You might have observed pollen grai ns with the help of the lens on the non-receptive surface of the sti ma. In young disc florets, the short st le below the ollen tube an d the rece tive surfaces of the two stigmas are pressed together so that pollen grains of the same lower cannot reach them. Later, in older disc florets, the style elongates, pushing the pollen grain out of the anther tube. And t e stigmas open out to expose the stigmatic (receptive) surface. B the time, the central young ones have reached the stage whe re only the pollen grains are released, the older disc florets (out r ones) have already got their stigmas above the stamens and their stigmatic surfaces are exposed. The honey-bee, which generally cau es pollination in sunflower first settles in the centre of the head (ca pitulum). It receives pollens all over its legs and under-surface a it walks outwards. You may o serve po en grains on t e egs an un er-sur ace o t e ee wit the help of hand lens. When the be reaches the older flowers, the pollen grains (obtained from other f lower heads) from its body are spread on the exposed stigmatic receptive surface and crosspollination is affected. If cross-pollination fails, the stigmas curl round to pick up their own pollen grains and thus secure self-pol lination.
Conclusion: Sunflower has following adaptive features for pollination: •Ray florets have coloured to attract insects as bees. •Nectaries are present at the base of the ovary to attract the pollinators. •Protandrous condition o the flower prevent self pollination. •The style elongates and the stigmatic surface is exposed only in older lower to ensure cross pollination. Adaptations for self Pollina ion cross-po na on a s, e s gmas cur roun o pick up their own pollen grains to ensure pollination.
II. SWEET PEA FLOWER
Experimental Procedure Take a flower of sweet pea (Lathyrus odoratus) cut a vertical section of the flower and study the structure and arrangement of floral parts. Observe flowering sweet pea p ant and find out what type of insect visit it.
OBSERVATION Sweet pea f lower has 5 f sed sepals. Corolla consists of 5 petals. The osterior petal is large called standard, t o lateral ones are called wings, two anteri r one unit to form a boat shaped structure called keel. n e ee are 10 s mens arrange n two groups 9 + 1. Filame ts of 9 stamen fused to form a filament tube in which nectar is secreted from the nectar y. Gynoecium is monocarpellary and consists of a long style, bent upwar s rouhly at right angle and bears the hair stigma. Pollination Like sunflower, sweet pe also shows protandry i.e. anthers m ture before stigma. The mature anthers burst when stigma is still . over them to suck necta from staminal tube and get pollen grains on their legs and abdomen in the process. But it is not able to pollinate the immature stigma. These pollen loaded bees when visit ature stigma of other plant, bring about successful pollination i.e., cross pol lination:
CONCLUSION Coloured petals of flower attract the insect to collect nectar from th m and promote cross-pollination which ecomes essential due to rotandr .
Comprehensive lab manual-Biology www.google.co.in www.howstuffwork.com Wikipedia Flower.org
• • • • •
