Agriculture Reference
In-Depth Information
TABLE 1.5
Correlation Coefficients (r) between Lowland Rice Grain Yield
and Tiller Number at Different Growth Stages
Parameter
1st Year
2nd Year
3rd Year
0.59**
0.41*
0.23
NS
Tiller number m
−2
at IT
0.69**
0.43*
0.34*
Tiller number m
−2
at AT
Tiller number m
−2
at IP
0.79**
0.59**
0.68**
Tiller number m
−2
at B
0.67**
0.52**
0.46**
Tiller number m
−2
at F
0.70**
0.37*
0.52**
Tiller number at PM
0.77**
0.48**
0.44*
Source:
Adapted from Fageria, N. K. and V. C. Baligar. 2001.
Commun. Soil Sci. Plant
Anal
. 32:1405-1429. With permission.
Note:
IT, initiation of tillering; AT, active tillering; IP, initiation of panicle; B, booting;
F, flowering; PM, physiological maturity.
*,**Significant at the 5% and 1% probability levels, respectively. NS, not significant.
The decrease in tiller number was attributed to the death of some of the last tillers as a result
of their failure in competition for light and nutrients (Fageria et al., 2011a). Another explanation is
that during the period of growth beginning with panicle development, competition for assimilates
exists between developing panicles and young tillers. Eventually, the growth of many young tillers
is suppressed, and they may senesce without producing seed (Dofing and Karlsson, 1993). A cor-
relation between grain yield and the number of tillers per meter square at different growth stages is
presented in Table 1.5. Tillering was related significantly with grain yield at all the growth stages;
however, the highest correlation in all the 3 years of experimentation was obtained at the initiation
of panicle growth stage. This means that the number of tillers determined at this growth stage had
more significance than that at any other growth stage in lowland rice.
A tiller number is quantitatively inherited. Its heritability is low to intermediate depending on
the cultural practices used and the uniformity of the soil. Although often associated with early vigor
in short-statured materials, the tiller number is inherited independently of all other major charac-
ters. In many crosses, tiller erectness or compactness is recessive to a spreading culm arrangement
(Jennings et al., 1997). Developing good plant types with high tillering capacity is rather simple.
Many sources of heavy tillering are available in traditional tropical rice cultivars. When their
culms are shortened, their tillering ability generally does not decrease and may increase (Jennings
et al., 1997).
1.2.1.3 Shoot Dry Weight
Shoot dry weight is an important growth trait in crop plants. N has significant influence in increas-
ing shoot dry weight of crop plants (Fageria, 2007; Fageria and Santos, 2008). Shoot dry weight of
lowland rice increased significantly in the vegetative as well as reproductive growth stages (Table
1.6). The increase in shoot weight is mainly associated with an increase in leaf and culm weights
during these growth stages. Rice plant weight mainly consists of organic matter such as protein and
carbohydrate. Carbohydrates are composed of cell wall substances such as cellulose and reserved
substances such as starch. The protein metabolism dominates in the vegetative growth stage and
carbohydrate metabolism does in the reproductive growth stage (Murayama, 1995). The portion
of inorganic matters in the weight of the rice plant is generally small. However, rice straw gener-
ally has high silicon content. In the mature shoot of rice, the silicon content can be as high as 10%
(Murayama, 1995).
