Zinnia

Zinnia is a genus of 20 species of annual and perennial plants of the family Asteraceae. They are native to scrub and dry grassland in an area stretching from the Southwestern United States to South America, with a centre of diversity in Mexico.^[3] Members of the genus are notable for their solitary long-stemmed flowers that come in a variety of bright colors. The genus name honours German botanist Johann Gottfried Zinn  Sun exposure: Full Sun Soil type: Any, Sandy, Loamy Flower color: Red, Pink, Orange, Yellow, Purple, White,Multicolor Bloom time: Summer Get a zing from zinnias! Zinnias are one of the easiest annuals to grow, grow quickly, and bloom heavily. They make a massive burst of color in your garden. Zinnias have bright, solitary, daisy-like flowerheads on a single, erect stem. The most common zinnia is "dahlia-flowered" and grows up to three feet. Other types are "cactus-flowered." Use in an annual or mixed border. Smaller zinnias are suitable for edging, windowboxes or other containers. The narrow-leaf zinnia also works well in hanging baskets. Zinnias are very popular for cut flowers. Planting Zinnias are grown from seed; they grow very quickly in the right conditions. Zinnias do not like to be transplanted. Full sun is essential wiht a minimum daylight temperature of 60 degrees F. Zinnias are adaptable but prefer fertile, humus-rich, well drained soil at pH preference 5.5 - 7.5. If soil is amended with compost, the flowers will grow more quickly. Sow seeds 1/4-inch deep. Space plants 4 to 24 inches apart depending on variety. (Many common varieties are 6 inches within the row and 2 feet in between rows.) See back of seed package. Germination occurs at 74 to 80 degrees F in 5 to 76 days. Sow in succession for a longer flowering display. Care Deadhead to prolong flowering. Maintain moderate soil moisture and fertilize lightly. Zinnias will die with the first frost. Pests Bacterial and fungal spots, powdery mildew, bacterial wilt. Minimize wetting of foliage to avoid disease. Caterpillars, mealybugs, and spider mites also cause problems. Avoid spraying and tolerate some leaf damage unless the situation is uncontrolled. Harvest/Storage Zinnias generally take 60 to 70 days from seed to flower (though it depends on conditions). Recommended Varieties Get a full-size flower on a compact plant with cultivars of the 'Dreamland Series.' Dwarf and compact, these zinnias have fully double flowerheads, to 4 inches across in a wide color range; stems are 8–12 inches tall. The 'Thumbelinia Series' cultivars and dwarf and spreading, with single or semi-double, weather-resistant flowerheads in many colors. Their petals are 1-1/4 inch across and stems grow up to 6 inches long. The 'State Fair Series' are the biggest and tallest of them all with large, double flowerheads that are 3 inches across. Stems grow to 30 inches tall. Special Features Attracts Butterflies Wit & Wisdom The small narrow-leaf zinnias make nice dried flowers, too.

Uses

A number of species of zinnia are popular flowering plants. Their varied habits allow for uses in several parts of a garden, and their tendency to attract butterflies and hummingbirds is seen as desirable.

process of flower formation

plant metamorphosis - environment controls how the plant changes phase change - internal development >> competence, ability to reproduce reproductive structures added on to existing structures distinct juvenile, adult phases easier to revert adult into juvenile than to induce phase change flower production pathways - 3 regulated pathways to flowering light-dependent (photoperiodic) pathway - length of day (amount of daily sunlight) affects flowering daylight shorter than critical length (12 hours) >> flowering in short-day plants (blooms in late summer/fall) daylight longer than critical length >> flowering in long-day plants (crop plants, blooms in spring/summer) day-neutral plants - flower when mature, regardless of day length 2 critical photoperiods >> will not flower if day too long/short facultative-long-or-short-day-plants - flower speed depends on day length cryptochrome/phytochrome detect photoperiods repress gene that represses flowering >> flowering takes place temperature-dependent pathway - cold temperatures >> faster flowering vernalization - shoots/seeds chill >> reproduce gibberellin hormones controls flowering, expression of certain genes.zzz

parts of the flower - no direct contact between pollen, ovule

• pollinators - animals that transfer pollen between plants
• complete flower - has all 4 whorls (calyx, corolla, androecium, gynoecium)
• perfect flower - has stamen/carpel (androecium/gynoecium)
• calyx - outermost whorl
  • contains the sepals (protects the flower in the bud)
• corolla - collective name for the petals
  • used to attract pollinators
• androecium - stamens in a flower
  • microsporangia on anthers
  • held up by filaments
• gynoecium - female flower parts
  • contains single/fused carpel
  • ovules - produced in the ovary, become seeds
  • stigma - receives pollen at top of carpel
  • style - connects stigma to ovary
  • floral specialization - floral parts either fused or reduced/lost
    • more advanced angiosperm >> less parts in each whorl
    • modifications sometimes due to pollination techniques (wind replaces animals)
    • artificial selection >> flowers less able to adapt
      • corn (maize) wouldn’t be able to survive as easily w/o human aid
    • floral symmetry - different between primitive/advanced flowers
      • primitive >> radial symmetry
      • advanced >> bilateral symmetry
    formation of angiosperm gametes - gametophytes completely enclosed by sporophyte
    • male gametophytes = microgametophytes, pollen grains
      • forms in 2 pllen sacs in anther
      • microspore mother cells - found in specialized chambers of sac
      • microspore mother undergoes meiosis >> haploid microspores >> 4 pollen grains after mitosis

 female gametophytes = megagametophytes, embryo sac forms in ovules megaspore mother cells - found in each ovule megaspore mother cell undergoes meiosis >> haploid megaspores, only 1 survive >> 8 haploid nuclei after mitosis 1 nucleus >> egg, rest arranged in precise locations (2 polar nuclei in middle of sac, 2 in synergids flanking egg, 3 in antipodal cells)

Pollination without insects

It's not always insects that pollinate the flowers; plants may use the wind, birds or even bats as pollinators! With wind-pollinated plants - such as grasses, cereals and some trees - the flowers are very simple, with no bright colours or nice smells as they don't need to attract the insects. These plants have both male and female reproductive parts and they make a lot of pollen. This is why a pollen allergy is called 'hay fever'.

Pollination by insects

An insect can pollinate flowers accidentally when the pollen is rubbed off the body of the insect. Plants can produce nectar within flowers, a sugary liquid, which many insects feed on. Pollen is a useful source of protein for some insects, such as bees. Insects are attracted to the flower by scent, colours and nectar. They carry pollen from flower to flower, while collecting nectar and pollen for themselves. After pollination, the plant produces a seed, which mostly grows protected inside the plants' ovaries.

What is pollination?

Pollination takes place when pollen lands on the stigma of a plant. It then travels down to the ovary and it's here that the ovules are fertilised. Most plants have flowers with the male and female parts present in each flower. Mostly, plants rely on insects, such as bees, to take the pollen from the anthers to the stigma.

flower defination

The reproductive structure of some seed-bearing plants, characteristically having either specialized male or female organs or both male and female organs, such as stamens and a pistil, enclosed in an outer envelope of petals and sepals.