Tolerance to Lime - Induced Chlorosis and Drought in Grapevine Rootstocks - Abiotic Stress: Plant Responses and Applications in Agriculture - page 279

soil depths. Distribution of root systems of individual rootstocks enables to identify their
uptake capacity for nutrients. This means that different rootstocks have a different capacity to
uptake individual nutrients from soil (Somkuwar et al., 2012).
Within the framework of their response to edaphoclimatic conditions individual rootstocks
also show differences in growth capacity of their roots, water uptake, transport of water into
annual shoots, metabolic activity and storage of carbon.
Water uptake and its transport represent one of the most important functions of roots. The
distribution of roots in soil and the root turnover are the key parameters of water uptake; they
are also important for the hydraulic redistribution (Bauerle et al., 2008a).
Root architecture refers to the spatial configuration of the root system, specifically focusing on
the geometric properties of root axes and laterals, mostly concerned with the entire root system
characteristics (Lynch, 1995). Typically, root distribution studies include root biomass or root
length as a function of soil depth, distance from the plant stem, and position between neigh‐
bouring plants (Bassoi et al., 2003).
The available soil volume is probably the most important factor dictating the size and the
distribution of root system (Saayman, 1982). The spatial root distribution is predominantly a
function of the soil environment, while root density is a function of rootstock (Southey &
Archer, 1988).
From the viewpoint of tolerance to abiotic factors associated with climatic and soil conditions
it is important to study and understand both vertical and horizontal distribution of roots in
soil. For example the Dog Ridge and Salt Creek rootstocks, which belong to Vitis champinii , put
forth prolific root systems of thickness of < 2 mm and 2-5 mm in the top depths of 0-30 cm up
to 60 cm away from the trunk, and later thicker roots of > 5 mm beyond 60 cm from the trunk.
However, St. George, which belongs to Vitis rupestris , has less root length in all categories at
all blocks horizontally up to a 150 cm distance from the trunk. In the vertical direction, Salt
Creek showed the greatest root length in the category of < 2 mm at a depth of 0-30 cm, while
Dog Ridge and St. George were at par for root length. However, at depths of 31-60 cm and
61-90 cm, Dog Ridge produced the greatest root length, followed by Salt Creek and St. George
(Simkuwar et al., 2012).
The rootstock shows a significant effect not only on the distribution of roots in soil but also on
the architecture of the root system. In Vitis rupestris, major roots create vertically a narrow angle
and can penetrate deep into the bottom soil layers. On the other hand, roots of Vitis riparia are
distributed in a wide angle and most of them are situated in a shallow top layer of soil (Perold,
1927). Swanepoel & Southey (1989) analysed the distribution of roots within a wider spectrum
of rootstocks growing under conditions of South Africa (Table 1).
Also abiotic factors may influence growth and development of the root system. In this case,
above all the vertical distribution of roots within the soil horizon is important.