Agriculture Reference
In-Depth Information
Exfoliation of sloughed epidermal and cortical cells is part of the normal growth
processes. These cells have a life span of a few weeks (Holden, 1975) and after their
death, cell walls and cytoplasm mix with the root and microbial mucilages adhering to
the extremity of the root to form the mucigel.
3.2.3.3
Chemical composition of exudates (sensu lato)
General pattern
Root exudates are basically a mixture of carbohydrates (simple sugars and polysaccha-
rides), amino compounds, organic acids, nucleotides, flavones, enzymes and growth
factors (see,
e.g.,
Smith, 1970; Rovira and Davey, 1974; Chaboud and Rougier, 1981;
Curl and Truelove, 1986) (Table III.9). The chemical diversity of exudates is compara-
ble to that of living cells since most cytoplasmic components have the capacity to
be leached. For example, Bowen and Theodorou (1973) identified 10 carbohydrates,
14 organic acids and 21 amino acids from the seedlings of ten forest species. Exudates
of seven species of cultivated plants (wheat, oats, maize, peas, lucerne, rice and peanut)
included 21 amino acids, 9 organic acids and 10 carbohydrates (Lespinat and Berlier,
1975). In both cases, significant differences among species were observed.
