Agriculture Reference
In-Depth Information
Box 8.3 Growth Rate Hypothesis
Short, cool growing seasons (f) are a disadvantage for plant growth. To over-
come and compensate for this disadvantage, the growth rate hypothesis
(GRH) predicts that natural selection will favor rapid growth in response to
increases in tissue nutrient concentration, especially phosphorus (P) because
of its critical role in the P-rich ribosomes required for protein synthesis (Elser
et al. 2000; Kerkhoff et al. 2005).
100
75
unfertilized
fertilized
50
Unwatered
25
100
75
50
6 mm/wk
25
100
75
50
25 mm/mo
25
MJ J
ASO
ND
JFMA
M
J
J
ASO
Fig. 8.4 Joint effects of fertilization and irrigation on desert evergreen plants. Open symbols ,
leaves emerging in spring; closed symbols , leaves emerging in autumn; wk weeks, mo months.
(From Lajtha and Whitford 1989)
 
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