Alternative Paths to Food Security - The Oxford Topic of Food, Politics, and Society - page 208

the plants' leaves, where they had significant effects on the plants' growth, physiology,
and productivity. Compared to rice plants that had no soil rhizobia living in their leaves,
rice plants inoculated with rhizobia exhibited a greater volume of roots and a greater
weight of the aboveground parts of the plant. Inoculated plants also had higher rates of
photosynthesis and greater water utilization efficiency, with twice as much photosyn-
thate produced per unit of water transpired. Rice plants with microbial inoculation had
grain yields 20 to 68 percent higher than the control plants' yield, with “crop per drop”
substantially increased.
The only difference associated with these changes in crop phenotype and productiv-
ity was whether the plants' leaves had become inhabited by soil organisms. In further
research, Chi et al. (2010) found that the presence of soil rhizobia in rice plants' leaf
tissues was correlated with the up-regulation of certain genes' expression in the leaves'
cells, producing more proteins that supported photosynthesis. Further, their presence in
root tissues and cells was found to correlate with producing more proteins that helped
protect rice plants against soil pathogens that can cause disease.
That soil bacteria infecting rice plants' leaves as well as their roots can raise grain yield
significantly suggests some shifting in the paradigm that we employ for understanding
and improving crop productivity (Uphoff et al. 2012). Crops' genetic potentials of course
are important; but the interactions between and among organisms within an ecosystem,
at both micro and macro scales, appear to be also important, even very influential.
Even more unexpected have been research results documenting beneficial effects for
the root growth of rice plant seedlings from “infecting” rice seeds with a certain fungus
( Fusarium culmorum ) before planting and germination (Rodriguez et al. 2009). This
fungus is known as a plant pathogen that causes a number of diseases in cereals, grasses,
and other plants. However, rice seeds inoculated with this fungus produced seedlings
with five times more early root growth, and root hairs emerged two days sooner, com-
pared to seedlings of same rice variety whose seeds were not inoculated with the fungus.
At ten days, the average weight of inoculated seedlings was 68 percent higher than for
seedlings from sterilized seeds with no microorganisms.
These studies open up an area for investigation rather than giving conclusive answers.
But they indicate that microbial endophytes, organisms living within plants in benefi-
cial or mutualistic associations rather than in parasitic relationships, can make signifi-
cant contributions to plant performance, which warrant more study (Uphoff et al. 2012).
Appreciation for what microorganisms contribute to plant growth and performance
parallels what is being learned in recent years about their contribution to animals,
including our own species Homo sapiens (Turnbaugh et al. 2007).
These and other findings suggest the importance of understanding plants as sys-
tems , rather than as discrete organisms. Plants depend, to an extent still inadequately
understood, on their associations with microorganisms in, on, and around their roots
and their shoots. Plants are not carbon-based, machine-like entities that are primarily
dependent upon our inputs, and whose genotypes need to be redesigned to become more
responsive to inputs that we provide them. Such a strategy forfeits some or many of the
benefits that can be reaped from providing plants with more conducive environments in