LEAF INITIATION RATES AND VOLUME GROWTH RATES IN THE SHOOT APEX OF CHRYSANTHEMUM

摘要: The leaf initiation rate and apical volume growth of lateral shoots Chrysanthemum inorifolium 'Improved Albatross III' were determined for plants growing under controlled environment conditions. After removal the terminal bud, top two buds produced leaves at a 1.4 to 1.6 leaves/day first 9 or 10 days. At about 10th day there appeared be an abrupt shift lower 0.7 0.8 leaves/day. Defoliation by periodic larger than 1 cm caused statistically significant increase in rate, but not as high that days bud growth. Volume rates region from transverse sections five apices, according method Richards (1951). was found have radial expansion 0.1623/plastochron vertical 0.0494/plastochron. calculated 0.3740/plastochron doubling time 1.85 plastochrons 56 63 hr. IN THE STUDY shoot several parameters can directly, these other derived. However, relatively few such quantitative studies apex been carried out. primordia wvhich grow away center dome directly (Richards, 1948, 1951). Other which could include ontogenetic seasonal changes cell volume. From information estimates made rates, division rates. This paper presents some vegetative chrysanthemum apex. overall objective this series determine rate(s) relate specific work presented determination degree constancy rate. MATERIALS AND METHODS-Culture plant mater-ial-Cuttings morzfolium Bailey provided Cal-Florida Propagators, Received publication 5 June 1968. Supported part National Science Foundation Cooperative Graduate Fellowship granted senior author University California, Davis, NSF Grant GB-6591 junior author; submitted doctoral dissertation. 2 Present address: U.S.D.A., Forest Service, Fire Laboratory, Riverside, California 92507. Fremont, Calif. rooted cuttings selected uniformitv size, vigor, root mass. They potted singly 4-inch clay pots potting mixture consisting 50 % sand, 25 peat, fir bark (Baker, 1957). then placed greenhouse 2-4 weeks watered daily with one-half-strength Hoagland's solution (Hoagland Arnon, 1950). again stem removed (pinched), leaving eight nine on plant. final selection homemade chamber. light intensity chamber 13001500 ft-c height. source 24 T-8 cool-white fluorescent 14 60-w incandescent bulbs 18 inches above plants. Daylength kept 20 hr continuous 4 darkness order provide maximum maintain state. Later increased, used later experiments grown 1800-2000 ft-c. higher compared light-intensity regime. temperature held constant ?4 1.5 C. solution. Leaf rate-The pinched quickly became dominant over buds. Because obvious differences between buds, only used. Samples 10-16 collected population intervals 3 beginning period (in all observations experi-