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.

Have you every looked closely at tree leaves in spring?  Our eyes are drawn to showy flowers and flitting birds, but a close look at emerging leaves shows some astonishing beauty. The most interesting thing about spring leaves is the intricate folding.  Leaves are often folded in half (as in redbud and hickory) or have complicated, compact folding schemes (as in oak and ash). Watching leaves emerge from their tight folding in buds to become full-grown leaves is fascinating.

Next time you are outside, have a look at some growing leaves. Visit the same plants over a few days and you will be amazed at the rapid changes you see.

Here are a few pictures of spring leaves in development (I will add more later).  Click on the pictures to see a high-resolution version.

bitternut hickory, Carya cordiformis. Leaflets are folded in half as the rachis (leaf stem) grows.

Yellow buckeye, Aesculus flava. Leaves emerge with the flowers. Leaflets are tightly rolled.

Eastern redbud, Cercis canadensis. Leaves are folded in half as they emerge, quickly unfolding.

northern red oak, Quercus rubra. Bright red leaves are compactly folded along sinuses. The leaves transition from red to green as they unfold.

Two pictures of green ash, Fraxinus pennsylvanica.  Leaflets are folded in half and folded against the rachis, spreading and unfolding as they develop.