Cuphea Production and Management - Industrial Crops: Breeding for BioEnergy and Bioproducts - page 298

Fig. 13.1 Cuphea PSR23 growth stages (Reprinted from Berti and Johnson [ 63 ]. With permission
from Elsevier)
533-578 GDD were required from planting to reach initial flowering [ 7 ] and about
1,200-1,350 GDD to reach harvest maturity [ 16 ]. Despite cuphea's indeterminate
growth, having a descriptive growth staging system, such as that for corn [ 72 ],
would be beneficial for making agricultural management decisions for its produc-
tion. Recently, Berti and Johnson [ 63 ] developed such a system for PSR23 cuphea
from emergence to harvest maturity that associates growth stages with accumulated
GDD and includes visual cues for key growth stage events (Fig. 13.1 ). For instance,
they defined initial flowering (R1) to occur between 600 and 800 GDD, physiolog-
ical maturity occurring around 900-1,000 GDD, and harvest maturity
(R5) occurring around 1,000-1,250 GDD [ 63 ]. This system greatly aids in the
timing of postemergence herbicide application and timing of harvest management.
Cuphea Water Requirements
Soil temperature and water are also critical factors that influence germination and
seedling establishment and subsequent plant growth and development. Field studies
have indicated that cuphea has low water use efficiency and may be susceptible to
drought [ 25 , 73 ]. A more recent study published by Gesch et al. [ 74 ] clearly showed
that cuphea seed and biomass production suffer from drought stress when the plant