
TY  - JOUR
A1  - Lisson, S. N. 
A1  - Mendham, N. J. 
A1  - Carberry, P. S. 
T1  - Development of a hemp (<emph type="2">Cannabis sativa</emph> L.) simulation model 2.The flowering response of two hemp cultivars to photoperiod
JF  - Australian Journal of Experimental Agriculture
JO  - Aust. J. Exp. Agric.
Y1  - 2000
VL  - 40
IS  - 3
SP  - 413
EP  - 417
KW  - hemp, model, phenology, flowering, photoperiod response.
UR  - https://doi.org/10.1071/EA99059 
N2  - The duration from sowing to flowering is an important determinant of fibre yield potential in hemp, since maximum stem yield occurs shortly after flowering. As a short-day plant, daylength has a key influence on the timing of flowering in hemp. This paper reports on studies into the effect of photoperiod on the thermal time duration from sowing to flowering for 2 hemp cultivars, and develops parameters to enable simulation of post-emergent phenology in the hemp model described in the final paper of this series. The hemp model divides the post-emergent period into a vegetative phase that ends at floral initiation, aflower development phase (FDP) between flower initiation and appearance, and a short phase between first flower appearance and harvest maturity (male anthesis). The vegetative phase is further divided into a temperature-dependent basic vegetative phase (BVP) and a daylength-dependent photoperiod induced phase (PIP). For a short-day plant, the duration of PIP is assumed to be zero degree days at daylengths below a base or maximum optimum photoperiod (MOP). Daylengths in excess of the MOP lead to an increase in thermal time within PIP, the duration of which is determined by a genotype&#8217;s photoperiod sensitivity (PS). Two hemp genotypes, Kompolti and Futura 77, were exposed to 6 different photoperiod regimes ranging from 8 to 16 h in a growth chamber. Thermal time durations from emergence to flower initiation and first flower formation (harvest) were calculated from thermograph plots. The flowering responses for the 2 cultivars were typical for a short-day plant, with flowering occurring rapidly in daylengths less than about 14 h and with increasing delay at longer photoperiods. With the exception of a longer thermal time duration from flower formation to harvest maturity in the case of Kompolti, the 2 cultivars had similar values for the key phenology parameters. Respectively, for Futura and Kompolti: BVP was 383&#x02DA;Cd and 390&#x02DA;Cd, MOP was 14 h and 13.8 h, PS was 266&#x02DA;Cd/h and 252&#x02DA;Cd/h, and FDP was 76.8&#x02DA;Cd and 80.2&#x02DA;Cd. 
ER  -

