9.2. Model Development
169
4.0 = conversion from light to sugar (microeinsteins/s quare
centimeter)
LeafArea = calculated average leaf area (square centimeter)
MaxSboot densuy» maximum shoo t density (#/s quare centimeter)
Nr_o!-shoots = total number of shoots in the population (#)
0.000000018 = conversion from micromoles of sugar to grams
(grams/ micromole)
The amount of sugar in above and below-groun d materials determines
the relative direction of sugar transfer. For example , if there is more sugar
available in the roots, then sugar will flow from the roots and rhizomes to
the shoo ts:
R&R_to_Shoot =Rbizkootta Sboot =Rbizkoot to Sboot'
=MAX(((R&R_CHO_concShoot;CHOJon c)/R&R_CHO_c onc))*0.05 *CHO_R&R,0).
0 )
Where:
R&R_to_Shoot = transfer of sugar from roots and rhizomes to shoo ts
(grams/ day)
R&R_CHO_con c =concentration of sugar in roots and rhizomes (grams/
liter)
ShooeCHO_conc =concentration of sugar in shoo ts (grams/ liter)
0.05 = rate of transfer (pe r day)
CHO_R&R = amou nt of sugar in roots and rhizomes (grams)
Conversely, if there is more sugar available in the shoots, then sugar will
flow from the shoots to the roots and rhizomes:
SboottoR b izlcoot =ShooC to_RhizRoot'-2
=IF Llg rounb =0 mEN 0 ELSE
MAX(((ShooeCHO_conc-R&R_ CHO_conc)/Shoot_ CHOJonc)
*O.l7*CHO_shoot,O).
(4)
Where:
Shoo ttoRbizkoot = transfer of sugar from shoots to roots and rhizome s
(grams/day)
Ll grouitb = growth of first leaf on new shoo t
ShooeCHO_conc = concentration of sugar in shoo ts (grams/ liter)
R&R_CHO_con c = concentration of sugar in roots and rhizomes (grams/
liter)
0 .17 = rate of transfer (pe r day)
CHO_shoot = amount of sugar in shoots (grams)
As stated, shoo t biomass also decreases through loss of leaves. Leaf loss is
the sum of discarded shoots calculated in the shoo t submodel (Figure 9.5):