root zone manipulation
Root System Grafting
Genetics control many functions
of a plant’s root system. Thus,
the ultimate form of root zone
manipulation is to graft a plant
onto different, more desirable
rootstock. Grafting involves
growing two separate seedlings:
one for the rootstock and one for
the scion (the plant top that gets
graphed onto new roots). The
scion plant is bred specifically for
its fruiting characteristics and
other traits, while the rootstock
seedling is bred specifically for
its desirable root zone. This root
zone has distinct advantages
over the scion’s natural roots,
including disease resistance,
improved nutrient uptake, and
plant/root vigor. These traits
allow the graphed plant to
better overcome unfavorable
growing conditions, including
heat and cold stresses.
Root zone grafting is most
commonly carried out in tomatoes,
peppers, cucumbers, aubergines,
and melons (though other hydroponic
crops may also be suitable). Studies
show that in hydroponic tomato
production, grafting can result in fruit
weight, number of fruit, and overall
yield increasing up to 27 per cent.
Grafted tomato plants also often
produce fruit with higher soluble
solids (sugars) and vitamin C than
non-grafted plants. Grafting as a
form of root zone manipulation is
particularly successful with heirloom
tomatoes, which naturally have lower
vigor and yields than commercial green-
house hybrid plants. Grafting heirloom
scions onto a good commercial rootstock
can significantly increase disease resistance
and boost yields, making a crop much more
economically viable.
While its possible for growers to graft their
own plants, they can also buy grafted
seedlings for evaluation in hydroponic
systems. Plant breeders continually
develop new and improved rootstocks
for many common hydroponic crops, and
these root zone genetic advantages could
soon be commonplace in many indoor
hydroponic gardens.
Chilling Root Zones
Root zone temperature plays as much of a role in plant
growth and development as the surrounding air. This is
because the root tissue sends numerous non-hydraulic
messages to the shoots, and these influence the way the
shoots respond to the environment.
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feature
“
THE ULTIMATE form of
root zone manipulation
is to graft a plant
onto different, more
desirable rootstock.”
Top: Chilling the nutrient solution, as is being done in this
aeroponic system in Singapore, allows for lettuce crop production
under tropical conditions.
Bottom: Root zone volumes are restricted in hydroponics
compared to plants grown in soil.