Sorry about the errant entry notification sent earlier today. I made some updates to that entry and the upgraded software decided that was enough to send out a new notification, so I’ll have to figure out how to suppress that in the future.
Here’s today’s entry, written by Connor:
Also known as orache and mountain-spinach, Atriplex hortensis can be found in cultivation worldwide. It is possibly native to central Asia, but the widespread cultivation obscures its origin. Mountain-spinach was formerly in the Chenopodiaceae before this entire family was included in the Amaranthaceae (via Wikipedia).
Plants For A Future Database reports a number of intriguing uses of orache. Not only do they taste like spinach, the leaves of mountain-spinach are suggested as an externally-applied remedy for gout. The seeds, when mixed with wine, are thought to be a possible treatment for jaundice.
Atriplex hortensis is a halophyte, meaning it grows well in saline soils. This is an increasingly valuable trait in cultivated plants, given the widespread use of irrigation. About one-half of the Earth’s land surface is “perennial desert or drylands” requiring irrigation for use in cultivation, a consequence of which is soil salinization (from Improving crop salt tolerance (PDF)). Irrigation salinity is “the rise in saline groundwater and the build up of salt in the soil surface in irrigated areas. Inefficient irrigation or applying more water than the plants can use means that this excess water leaks past the root zone to groundwater (recharge). This excess water can cause the watertable to ‘mound’ under irrigation areas and in some cases the ground becomes waterlogged.”
Species of Atriplex are able to tolerate saline soils because they concentrate the accumulated salt in specialized cells on the leaf surface called trichomes (from Vesiculated Hairs: A Mechanism for Salt Tolerance in Atriplex halimus L. (PDF)). In Introduction of a Na+/H+ antiporter gene from Atriplex gmelini confers salt tolerance to rice, the ability of transgenic rice plants to tolerate saline soil was evaluated. A gene from Atriplex responsible for a protein pump which transports salt ions across the cell membrane and the vacuole membrane was incorpoarated into rice plants. The transgenic plants were more tolerant of saline conditions not because they transported more ions into their cells reducing water loss through osmosis, but because they were able to transport more salt into the vacuoles of individual cells. Older leaves of the transgenic plants died because of this but the younger leaves continued to grow.