THE EFFECTS OF PHOTOPERIOD, TEMPERATURE, AND LIGHT INTENSITY ON THE GROWTH OF THE LOWBUSH BLUEBERRY (VACCINIUM ANGUSTIFOLIUM AIT.)

Abstract

A study of the effect of environmental factors on the growth and development of the lowbush blueberry was carried out using clonally propagated plants. In a preliminary study a definite photoperiodic response was found. Under 8-hour days flower buds were formed and no vegetative growth occurred. Under 16-hour days vegetative growth resulted and no flower bud formation occurred. In a replicated greenhouse experiment, seven clones produced flower buds with 8-, 10-, and 12-hour days, but produced none with 14- or 16-hour days. One clone produced flower buds with 8-, 10,- 12-, and 14-, but none with 16-hour days. Two clones were able to produce flower buds under all five photoperiods. Under 8- and 10- hour photoperiods no vegetative growth occurred. Under 12, 14, and 16 hours progressively more vegetative growth occurred. In an experiment on the interaction of temperature and photoperiod, vegetative growth was significantly greater at 70° F than at 50° F with the differences being accentuated by day length. Flower bud formation occurred with 11- and 13-hour photoperiods regardless of temperature, but was more pronounced at the higher temperatures. At 70° F, 15-hour photoperiod, no flower buds were formed while at 50° F, 15 hours, three clones produced no flower buds and six clones produced an abnormal type of inflorescence. Similar abnormal inflorescences were produced by giving plants 2, 3, or 4 weeks of 8-hour days. Six weeks of 8-hour days was sufficient to initiate normal inflorescences. Shade, provided by two layers of cheesecloth, significantly reduced the number of flower buds compared with full sunlight. The growth of the lowbush blueberry under field and laboratory conditions is discussed in relation to environmental factors.