Poplar trees (genus Populus, not to be confused with yellow-poplar, Liriodendron tulipifera) are among the fastest-growing trees in the world, and represent a diverse wide-spread genus of trees.  Poplars are grown in plantations for pulp and paper, and have great potential as feedstock for biofuels production.

Poplars have a lot of advantages as experimental plants, as they grow clonally from cuttings  and are easy to hybridize.  The poplar genome has been sequenced, making poplars even more attractive as research subjects and for advanced breeding.

Gary Coleman and his colleagues at the University of Maryland and Bowie State University have just received a $3.2 million grant from the National Science Foundation to take advantage of the poplar genome map to try to improve the prospects for poplars as a biofuel feedstock. 

Coleman’s group will use the poplar gene map to examine details about how poplars store and use nitrogen. Nitrogen is often the most limiting element in crop productivity, and trees are already fairly efficient at nitrogen use.  Understanding the molecular details of how poplars use nitrogen may help increase productivity of poplar plantations with minimal nitrogen input.

Poplars already have advantages over more familiar biofuel crops such as switchgrass and Miscanthus.  Poplars can grow on marginal farmland unsuitable for food production, minimizing competition between biofuels and food crops.  Increasing the nitrogen efficiency of poplar plantations is an important step in making biofuel production economically viable.

The annual maple sap flow has begun early in parts of Maine. According to the Bangor Daily News, mild day and night temperatures and a lack of snow is having a strong effect on Maine’s maple syrup industry.  The average start date for sap flow in Maine is March 20, with central Maine beginning March 7-10.

This year, sap flow is already strong in parts of the state, while daytime temperatures are still too low in other areas.  The forecast for this year’s production is unpredictable because of the strange weather patterns.

Sap flow in maples occurs when warm days and cold nights stimulate conversion of starch to sugar, and the osmotic potential created by high sugar concentrations in sap draws water in from the soil.  This creates a positive pressure in the xylem, allowing sap to flow from cuts in the stem.

Global warming is predicted to drive sap production further north, as spring weather warms more quickly.  Average night-time temperatures are increasing throughout New England, and this does not bode well for the long-term prospects for the US maple syrup industry.  However, 2009 was a record year for syrup production in Maine following a disastrous 2008. 

Here is a list of all the plants that we ate this Thanksgiving dinner. We made our usual dinner for 10 people, family and guests. Below the plant list is a list of the dishes we made.  Corn appears in many items that may not be obvious, such as mashed potatoes. However, turkey and dairy products are made from animals fed almost entirely on corn. So any item containing dairy products is listed as containing corn. The total number of plants is 42, though a few are different varieties of the same species. Sugar is of two potential sources, sugar cane and beet sugar. It happens that all the sugar we have on hand is cane sugar. Sugar not labeled as cane sugar is generally beet sugar.

We’d be interested in any other plants that you might have eaten this Thanksgiving. Please add in comments, and tell us both what plant you used (don’t worry about the species name and family) and in what dish you used the plant. 

Dishes:

When I was an undergraduate, one of my favorite courses was a seminar in biological clocks and circadian rhythms taught by Hugh Wilcox at Syracuse.  Biological clocks have fascinated biologists since the 19th century, but until recently it was not possible to look at the mechanisms underlying daily variation in behavior.  With the advent of molecular biology, it is now possible to look directly at genes expressed at various times of day. The trick is to separate gene expression that is cued by an external signal, like sunrise, from gene expression cued by an organisms internal clock.

Charles Darwin was probably the first to recognize that plants vary through the day and night in the rate of growth and movement. Most often, plants grow more at night than during the day.

Using DNA microarrays, Todd Michael and his colleagues have found that a group of genes related to expression of plant growth regulators in Arabidopsis are at a maximum during the night and are associated with a growth spurt just before dawn.  The peak in gene expression was associated with expression of phytohormone regulatory elements.  It appears that peaks in growth during the night are related to circadian variation in expression of regulatory elements with external cues (light and dark periods) setting the clock.

This research contributes to our rapidly increasing body of knowledge about how plants regulate themselves and optimize their use of resources throughout the day-night cycle.

Citation:

Michael TP, Breton G, Hazen SP, Priest H, Mockler TC, et al. 2008 A Morning-Specific Phytohormone Gene Expression Program underlying Rhythmic Plant Growth PLoS Biology Vol. 6, No. 9, e225 doi:10.1371/journal.pbio.0060225

Links:

News Release: ‘Biological Clock’ Genes Control Plant Growth