Agriculture Reference
In-Depth Information
TABLE 1.17
Maximum Root Length (MRL) and Root Dry Weight (RDW)
of 61-Day-Old Corn Plants as Influenced by N Levels
N Rate (mg kg
−1
)
MRL (cm)
RDW (g per plant)
0
42.75
1.19
100
40.75
1.60
200
35.50
1.44
400
33.25
1.09
600
27.75
0.52
F-test
**
**
CV (%)
8.78
16.73
Regression Analysis
N rate versus MRL = 42.77 - 0.03X + 0.0000095X
2
, R
2
= 0.88**
N rate versus RDW = 1.29 + 0.0019X - 0.0000054X
2
, R
2
= 0.77**
**Significant at the 1% probability level.
2001). Rice (2007) reported that the essential nature of N as a plant nutrient is based primarily on
its role as a component of enzymes, which are either entirely protein or largely composed of protein.
Enzymes catalyze virtually every anabolic reaction (formation) and catabolic reaction (breakdown)
within the plant and orchestrate the rate, timing, direction, and extent of most metabolic reaction
pathways. Approximately, a large part of the total N (80-85%) in green plant material is sequestered
in protein (Rice, 2007). The remaining is distributed in nucleic acids (about 10%) and across the
soluble metabolic pool of amino acids (about 5%) and their amines and amides (Mengel et al., 2001).
Unlike humans, plants synthesize all transaminases needed to produce the 20 specific amino acids
required for the synthesis of all required plant proteins (Rice, 2007).
FIGURE 1.19
Root growth of corn at different N levels.
