Photorespiration

Photorespiration

occurs when the CO2 levels inside a leaf become low. This happens on hot dry days when a plant is forced to close its stomata to prevent excess water loss. If the plant continues to attempt to fix CO2 when its stomata are closed, the CO2 will get used up and the O2 ratio in the leaf will increase relative to CO2 concentrations.
When the CO2 levels inside the leaf drop to around 50 ppm, Rubisco starts to combine O2 with RuBP instead of CO2.
The net result of this is that instead of producing 2 3C PGA molecules, only one molecule of PGA is produced and a toxic 2C molecule called phosphoglycolateis produced.

The plant must get rid of the phosphoglycolate
First it immediately gets rid of the phosphate group, converting the molecule to glycolic acid. The glycolic acid is then transported to the peroxisome and there converted to glycine.
The glycine is then transported into a mitochondria where it is converted into serine.
The serine is then used to make other organic molecules. All these conversions cost the plant energy and results in the net lost of CO2 from the plant.
To prevent this process, two specialized biochemical additions have been evolved in the plant world: C4 and CAM metabolism

("auxano" -- "I grow").

uxins derive their name from the Greek word αυξανω ("auxano" -- "I grow"). They were the first of the major plant hormones to be discovered and are a major coordinating signal in plant development. Their pattern of active transport through the plant is complex. They typically act in concert with (or opposition to) other plant hormones. For example, the ratio of auxin to cytokinin in certain plant tissues determines initiation of root versus shoot buds. Thus a plant can (as a whole) react on external conditions and adjust to them, without requiring a nervous system. On a molecular level, auxins have an aromatic ring and a carboxylic acid group (Taiz and Zeiger, 1998).
The most important member of the auxin family is indole-3-acetic acid (IAA). It generates the majority of auxin effects in intact plants, and is the most potent native auxin. However, molecules of IAA are chemically labile in aqueous solution, so IAA is not used commercially as a plant growth regulator.
Naturally-occurring auxins include 4-chloro-indoleacetic acid, phenylacetic acid (PAA) and indole-3-butyric acid (IBA).
Synthetic auxin analogs include 1-naphthaleneacetic acid (NAA), 2,4-dichlorophenoxyacetic acid (2,4-D), and others

uxins are often used to promote initiation of adventitious roots and are the active ingredient of the commercial preparations used in horticulture to root stem cuttings. They can also be used to promote uniform flowering, to promote fruit set, and to prevent premature fruit drop.
Used in high doses, auxin stimulates the production of ethylene. Excess ethylene can inhibit elongation growth, cause leaves to fall (leaf abscission), and even kill the plant. Some synthetic auxins such as 2,4-D and 2,4,5-trichlorophenoxyacetic acid (2,4,5-T) have been used as herbicides. Broad-leaf plants (dicots) such as dandelions are much more susceptible to auxins than narrow-leaf plants (monocots) like grass and cereal crops. These synthetic auxins were the active agents in Agent Orange, a defoliant used extensively by American forces in the Vietnam War.

Ashwagandha

Common name: Winter Cherry • Hindi: Ashwagandha अश्वगंधा, Rasbhari • Kannada: Kanchuki • Marathi: Ghoda, Tilli • Gujarati: Ghodaasun • Telugu: Vajigandha • Malayalam: Amukkuram • Tamil: Amukkuram Botanical name: Withania somnifera Family: Solanaceae (Potato family)
Ashwagandha, is native to drier parts of India. It is a perennial herb that reaches about 6 feet in nature. In the greenhouse they flower in the late fall and winter. Orange fruits in persistent papery calyxes follow the small greenish flowers. Ashwagandha is propagated by division, cuttings or seed. Seed is the best way to propagate them. Seed sown on moist sand will germinate in 14-21 days at 20° C. A postal stamp was issued by the Indian Postal Department to commemorate this flowers. Medicinal uses: Ashwagandha has been a prized top notch adaptogenic tonic in India for 3000 - 4000 years. The plants contain the alkaloids withanine and somniferine, which are used to treat nervous disorders, intestinal infections and leprosy. All plant parts are used including the roots, bark, leaves, fruit and seed.