Feeding the World in 2050

Forty years from now will there be enough food to supply the world’s growing human population? Perhaps the best answer is “It depends”. It depends on how much we can improve the energy efficiency of producing and transporting food. It depends on what we are willing to eat (“Excuse me sir – would you like the beef or the crickets?”). It depends on what we do about climate change, how much damage we do to the environment, and how efficiently we use our precious supplies of fresh water. It depends on whether we’re willing to use genetically modified crops.

A special section of Science magazine available online examines some of these and other issues on the subject of food security. There are some pretty interesting and thought-provoking ideas out there. There’s even an article on what kinds of careers might be available for persons interested in this subject.

Basalt and granite

I think it was Whitney who asked a question about the relationship between basalt rock and granite rock. It turns out that this is key to understanding which plate 'wins' when they collide. Basalt rock is heavier and granite is lighter. Plates made of basalt tend to be forced under the lighter granite plates. The lighter granite plates form the continents. Basalt and granite are addressed here at the Ask a Geologist page. The analogy seems backwards though - the heavier truck ends up on top of the lighter VW whereas the heavier basaltic plate ends up underneath the lighter granitic plate.

As it turns out, most of the ocean floor is basalt, and most of the continents are granite. Basaltic crust is dark and thin and heavy, while granite is light and accumulates into continent-sized rafts which bob about like corks in this "sea of basalt." When a continent runs into a piece of seafloor, it's much like a Mac truck running into a Volkswagon. Not very pretty, but at least there's a clear winner. And the seafloor basalt ends up in pretty much the same position as does the VW - under the truck (or continent, as the case may be). This may seem like a drag for the basalt, but remember that it isn't all that happy on the surface anyway, and this gives it the heat it needs to re-melt and try to complete the differentiation process which was so rudely interrupted at the spreading ridge. If successful and allowed to continue, what's left behind is a "purified" magma with most of the iron, magnesium, and other heavy elements removed. When it cools, guess what forms? And the continental land mass just got a wee bit larger.

The following YouTube video from National Geographic is a little dramatic and they fail to mention now speculative the positions of the early continents are but even so I thought I'd post it because it nicely covers several topics we looked at from the bombardment of the earth, to the origin of life, to the production of heat via radioactivity and the movement of the plates.

Can a single layer of cells control a leaf's size?

Found this online and thought it was interesting. Especially because we were talking a lot about what makes the plants growing longer on one side.

http://www.biologynews.net/archives/2010/02/25/can_a_single_layer_of_cells_control_a_leafs_size.html

Ever looked carefully at the leaves on a plant and noticed their various sizes and shapes? Why are they different? What controls the size and shape of each individual leaf? Very little is known about the developmental control of leaf size and shape, and understanding the mechanisms behind this is a major issue in plant biology.


A leaf's size is determined by a combination of cell number, cell size, and intercellular space. Michael Marcotrigiano from Smith College, Massachusetts, wanted to find out what role cell layers played in regulating leaf size and shape. He utilized a powerful tool—the synthesis of graft chimeras—that has allowed him to carefully analyze the developmental regulation of leaf size and shape in Nicotiana and has published his findings in the February issue of the American Journal of Botany (http://www.amjbot.org/cgi/content/full/97/2/224).

By grafting plants of different Nicotiana genotypes Marcotrigiano was able to recover shoots from the graft union that were chimeras. These shoots were composed of both genotypes. Eventually he recovered leaves with two genetically distinct cell layers. He grafted N. tabacum, a large-leaf genotype, and N. glaucum, a small-leaf genotype, to produce leaves where the resulting epidermal cell layer was a different genotype than the mesophyll cell layer—but on only one side of the leaf, allowing for direct comparison of the growth of the leaf from one side to the other. Thus, one side of the leaf could act as a "control" for the other side of the leaf. This enabled him to set up some nicely designed comparisons where on one side of the leaf the outer cell layer (the epidermis) differed in genotype from the rest of the leaf.

"Since leaves generally vary in size along the length of the stem and leaf size is strongly influenced by environmental factors, my method allowed me to compare one side of a leaf to the other, negating the complications that arise when comparing different leaves on a single plant or leaves on different plants," Marcotrigiano said.

Creating these graft chimeras was time-consuming and involved an element of chance; often the growing tip of the chimeral shoots reverted back to a non-chimeral shoot rendering the leaves generated from that point on useless for analysis. However, over the past decade enough leaves were recovered that were perfectly bisected, homogeneous on one side of the midvein and with a unique epidermis on the other. This allowed Marcotrigiano to use them to examine how leaf cell layer affects leaf size and shape.

Marcotrigiano's most striking finding was the important role that the epidermal cells played in determining leaf size. He found that leaves grew asymmetrically when one side of the midvein contained identical cell layer arrangements and the other side contained epidermal cells that differed genetically from the mesophyll cells. When big-leaf epidermal cells surrounded small-leaf mesophyll cells in an otherwise all small-genotype leaf, the big-leaf epidermal cells caused that side of the leaf to be bigger than the other side. In contrast, when small-leaf epidermal cells surrounded big-leaf mesophyll cells in an otherwise all big-genotype leaf, the small-leaf epidermal cells caused that side to be smaller than the other side.

Epidermal cells not only controlled overall leaf size, but also influenced the number of cells produced in the mesophyll layer. For example, small-leaf epidermal cells surrounding big-leaf mesophyll cells caused the mesophyll cells to have many fewer cell divisions than when they were surrounded by big-leaf epidermal cells. Interestingly, the epidermal cells did not influence, or change, the size of the mesophyll cells.

Marcotrigiano concludes that while regulation of leaf size is complex and influenced by many factors and many genes, his findings show that communication between adjacent cell layers plays an important role in determining leaf size. Cells in one tissue layer can control the rate of division of cells in another tissue layer, which in turn influences overall leaf size.

Source : American Journal of Botany

More Lotusland

More photographs courtesy of Lauren. Again, click for a larger version of the contact sheet.
Here are a couple of my favorites in all their glory:
DSC_5187 - lemons
DSC_5193 - rain

I uploaded some more photos from the first contact sheet. See the post below.

Lotusland Pictures

Lauren sent me some great pictures she took at Lotusland. I made a contact sheet out of them (fyi Photoshop will do this automatically for you using File> Automate> Contact Sheet if you have a directory full of photo images) and if you click on the image you should get a slightly larger version.

I uploaded a number of the photographs at their full size and they are available here:
CSC_5355.JPG
DSC_5095.JPG
DSC_5099.JPG
DSC_5114.JPG
DSC_5128.JPG
DSC_5132.JPG

I'll upload a second contact sheet and some more full size images shortly.

Earthquake in Chile shifts Earth's axis

Hopefully it's common knowledge by now that there was an earthquake in Chile over the weekend. Upon learning the magnitude of an earthquake my thoughts generally drift toward concern for the people of that region. However, in addition to the 700+ people who died and many who were injured, the Earth took a toll as well, slightly shifting its axis in response to the quake. As a result, it is estimated that days on Earth have been shortened by about 1.26 microseconds. While the change is seemingly negligible, I found it interesting that it could happen at all.

Here's the link to the NASA report:

http://www.nasa.gov/topics/earth/features/earth-20100301.html

Ancient plant has hot, stinky sex

If you go into science journalism you too can get to write headlines like this:
Ancient plant has hot, stinky sex
The actual paper this news article is based on has the decidedly more prosaic title of:
Odor-Mediated Push-Pull Pollination in Cycads
The reproductive organs of some plants self-heat, release scent, and attract pollinators. The relations among these processes are not well understood, especially in the more ancient, nonflowering gymnosperm lineages. We describe the influence of plant volatiles in an obligate pollination mutualism between an Australian Macrozamia cycad (a gymnosperm with male and female individuals) and its specialist thrips pollinator, Cycadothrips chadwicki. Pollen-laden thrips leave male cycad cones en masse during the daily thermogenic phase, when cone temperatures and volatile emissions increase dramatically and thrips are repelled. As thermogenesis declines, total volatile emissions diminish and cones attract thrips, resulting in pollination of female cones. Behavioral and electrophysiological tests on thrips reveal that variations in b-myrcene and ocimene emissions by male and female cones are sufficient to explain the observed sequential thrips' repellence (push) and attraction (pull). These dynamic interactions represent complex adaptations that enhance the likelihood of pollination and may reflect an intermediate state in the evolution of biotic pollination.