Types of GYMNOSPERMS
Angiosperms produce flower
Gymnosperms have odd seed container such as pine cones
Around 550 species of conifer trees exist worldwide and make up the largest group of gymnosperms. Conifers may be evergreen or deciduous
Examples of evergreen conifers include:
Their cones may be hard and dry, such as with pine and spruce trees, or fleshy, like with junipers.
Some conifers lose their needles or scaly leaves in winter:
Conifers tend to inhabit colder and drier habitats around the world.
Plants adapt through chemical signals
The three key pigments in photosynthesis: chlorophyll a, chlorophyll b, and β-carotene, to absorb darker frequencies of light a plant may produce more pigments that absorb dimmer light and become darker or appear red.
Auxin hormones help plants detect light, however, auxins are toxic to plants in large concentrations; they are most toxic to dicots and less so to monocots.
Auxins are used to produce seedless fruit.
Synthetic auxin herbicides, including 2,4-D and 2,4,5-T, have been developed and used for weed control, 2,4-D is a synthetic auxin.
The defoliant Agent Orange, used extensively by British forces in the Malayan Emergency and American forces in the Vietnam War, was a mix of 2,4-D and 2,4,5-T. The compound 2,4-D is still in use and is thought to be safe, but 2,4,5-T was more or less banned by the U.S. Environmental Protection Agency in 1979. The dioxin TCDD is an unavoidable contaminant produced in the manufacture of 2,4,5-T. As a result of the integral dioxin contamination, 2,4,5-T has been implicated in leukemia, miscarriages, birth defects, liver damage, and other diseases.
Talking to Plants