Growth, opium gum yield, and photoperiod response of five opium poppy accessions

Flowering time, growth, and opium gum yield from five seed sources (T, L, B 1, B3, B3) of opium poppy (Papaver somniferum L,) collected from different latitudes in three Southeast Asian countries were determined, Plants were g rown in six growth chambers at a 11-, 12-, 13-, 11-, 15-, or 16-hour photop eriod with a 12-hour, 25/20 degrees C thermoperiod, Flower initiation was o bserved under a dissecting microscope (40x) to determine if time to floral initiation was identical for all accessions across a wide range of photoper iods. The main capsule was lanced for opium gum at 10,13, and 16 days after flowering (DAF). Plants were harvested at 21 DAF for plant height, leaf ar ea, and organ dry-weight determinations. In a 16-hour photoperiod, flower i nitiation was observed 10 days after emergence (DAE) for B1 vs. 8 DAE for t he other four accessions. Flowering time was affected most by photoperiod i n B1 and least in B2, Flowering times for B3, L, and T were similar across the range of photoperiods, B2, B3, and L had the highest gum yields per cap sule; even though B1 had the greatest total plant biomass it produced the l owest gum yield, There was no difference among accessions in the average ra tio of gum : individual capsule volume, For the ratio of gun : capsule dry weight, only the difference between T and B1 was significant, Capsule size did affect these ratios slightly. T had a larger gum : volume ratio for lar ger capsules, and B3 had a smaller gum : dry-weight ratio for heavier capsu les, Flowering time varied up to 40%, capsule dry weight up to 41%, and opi um gum yield up to 71% for the five accessions across all treatments. No re lationship was found between flowering time and the latitude where the seed sources were collected, Time to flower initiation could not be used to pre dict time to anthesis because floral development rates varied significantly among accessions and photoperiods, Capsule volume and dry weight were usef ul in estimating gum yield.