Agriculture Reference
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in number of spikes per plant per year, number of florets per spike, maxi-
mum average yield of spikes per plant, spike length and a B:C ratio of 2.38
which were significantly higher compared to control.
Gardeners know how color in the flower garden depends on changes in
the weather. Many, but not all, species are triggered into flower by high-
er temperatures. Miller and Primack, (2008) in a recent study compared
flowering times and found that there had been an average rise of 2.4 °C
and also found that plants were flowering about a week earlier than 150
years ago. Naturally this figure masked huge variations between species
and even between closely related species. Sweet birch, Betula lenta, for
example, now flowers 3 days earlier for every increase of 1 °C, while the
Gray birch catkins,
Betula populifolia
have been advanced by 11 days for
each degree. In a study on effect of higher temperature on flower colo-
rand changes in the content of the main anthocyanins. Results revealed
that poor coloration of flowers was observed at 30 °C in all genotypes
except 'Chatoo.' All genotypes showed lower contents of the two antho-
cyanins tested [cyanidin 3-O-(6”-O-monomalonyl-beta-glucopyranoside)
and cyanidin 3-O-(3”,6”-O-dimalonyl-beta-glucopyranoside)] at higher
temperatures (Nozaki et al., 2006). It found that flowering was delayed in
all cultivars of spray chrysanthemum as day length increased from 13 to
14 h and abnormal flower formation was induced at over 13 h day length.
These results suggest that there were formation of abnormal flowers and
delay in flowering under high temperature. Delayed flowering of chrysan-
themum under hightemperature conditions is a serious obstacle for all-
year-round cut chrysanthemumflower production in southern temperate
and subtropical zones. In a study of Nozaki and Fukai (2008) two dif-
ferent genotypes of spray chrysanthemum (
Dendranthema grandiflorum
syn.
Chrysanthemum morifolium
) were grown under high-temperature
conditions: summer-to-autumn flowering type (SA type, hightemperature
tolerant) and autumn flowering type (A type, hightemperature sensitive).
Results showed that high temperatures slowed floral development in in-
florescence, thereby increasing the number of florets in both SA and A
chrysanthemum genotypes. Secondly, high temperatures slowed the de-
velopmental speed of inflorescence after the budding stage, and the time to
reach the bud break stage was prolonged, thereby delaying flowering. Eun
Joo et al. (2004) found that chrysanthemums that were exposed to high
temperature developed two types of abnormal flowers, that is, formation
of ray florets only and formation of ray florets with bracts at the center of
