Agriculture Reference
In-Depth Information
Endophytes regulate plant growth and development
Eudiocots (tomato)
S (40 cm)
ative species (switchgrass)
NS (20 cm)
NS
S
Monocot (rice)
NS
S
FIGURE 6.2
Endophyte-induced growth responses in eudicot and monocot plants.
Nonsymbiotic (NS) and symbiotic (S) plants are the same age in each panel. Difference in
biomass between NS and S plants varied from 2× (tomato) to 10× (rice). Tomato plants were
grown under field conditions, and the others in a growth chamber.
Growth and development of inoculated plants could also be accelerated by
increased metabolic efficiency so that more biomass is produced per photosynthet-
ically derived carbon building block. This could occur as a result of endophytes
influencing plants' gene expression so that some genes are up-regulated and more
biochemical building blocks become available for tissue generation. To address this
possibility, the overall gene expression patterns and metabolic activity were ana-
lyzed in symbiotic and nonsymbiotic plants. This research indicated increases in the
number of up-regulated plant genes in symbiotic versus nonsymbiotic plants when
grown in the absence of abiotic stress (Woodward et al. 2012). However, metabolic
activity as measured by differential scanning calorimetry revealed little to no dif-
ference in either metabolic rates or efficiencies between symbiotic and nonsymbiotic
plants (rice or tomato). Thus, there was no apparent relationship between the number
of up-regulated genes and metabolic activity or efficiency and the growth metrics in
symbiotic plants.
Comparative analysis of photosynthetic activity in symbiotic and nonsymbi-
otic plants yielded similar results to the metabolic studies (Woodward et al. 2012).
Although there were no measureable differences in photosynthetic rates or stomatal
activity, symbiotic plants had significantly greater levels of photosynthetic efficiency
than nonsymbiotic plants. This suggests that symbiotic plants more efficiently trans-
fer energy from photons into C building blocks, and therefore have greater amounts
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