Feeding the world (and saving nature) in this populous century, Jane Langdale 
began, depends entirely on agricultural efficiency — the ability to turn a 
given amount of land and sunlight into ever more food.  And that depends on 
three forms of efficiency in each crop plant: 1) interception efficiency 
(collecting sunlight); 2) conversion efficiency (turning sunlight into sugars 
and starch); and 3) partitioning efficiency (maximizing the edible part).  Of 
these, after centuries of plant breeding, only conversion efficiency is far 
short of the theoretical maximum.  The photosynthesis in most plants (called 
“C3“) is low-grade, poisoning its own process by reacting with oxygen instead 
of carbon dioxide when environmental conditions are hot and dry.

But some plants, such as corn and sugar cane, have a brilliant workaround.  
They separate the photosynthetic process into two adjoining cells.  The outer 
cell creates a special four-carbon compound (hence “C4“) that is delivered to 
the oxygen-protected inner cell.  In the inner cell, carbon dioxide is released 
from the C4 compound, enabling drastically more efficient photosynthesis to 
take place because carbon dioxide is at a much higher concentration than oxygen.

Rice is a C3 plant — which happens to be the staple food for half the world.  
If it can be converted to C4 photosynthesis, its yield would increase by 50% 
while using half the water. It would also be drought-resistant and need far 
less fertilizer.

Langdale noted that C4 plants have evolved naturally 60 times in a variety of 
plant families, all of which provide models of the transition.  “How difficult 
could it be?” she deadpanned.  The engineering begins with reverse-engineering. 
 For instance, the main leaves in corn are C4, but the husk leaves are C3-like, 
so the genes that affect the two forms of development can be studied.  
Langdale’s research suggests that the needed structural change in rice can be 
managed with about 12 engineered genes, and previous research by others 
indicates that the biochemical changes can be achieved with perhaps 10 genes.  
The genes needed for the eventual fine tuning will emerge later.

When is later?  The C4 Rice project began in 2006 at the International Rice 
Research Institute in the Philippines, funded by the Bill & Melinda Gates 
Foundation.  The research is on schedule, and engineering should begin in 2019, 
with the expectation that breeding of delicious, fiercely efficient C4 rice 
could be complete by 2039.

It is the kind of thing that highly focussed multi-generation science can 

                                                                —Stewart Brand  
s...@longnow.org <mailto:s...@longnow.org>

[An illustrated, linkable version of this summary is on Medium, here 

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