Biology Reference
In-Depth Information
Table 1.
Composition of LxS8 nectar. Nectar from LxS8 plants was analysed by a variety of
methods and these components have been identified as significant nectar constituents.
Volume (µl)
24
Protein (µg/ml)
240
Sugars (M)
Sucrose
0.55
Glucose
0.47
Fructose
0.43
Amino acids (µM)
Proline
2,020
Tyrosine
547
Serine
319
Asparagine
114
H
2
O
2
(mM)
4
Ascorbate (µM)
920
due to the accumulation of β-carotene. The duration of the ripening stage is
approximately 12-24 h.
Nectary maturation
occurs from floral stage 9
through floral stage 12, during which nectar proteins begin to be synthesized.
Nectar flow begins at late stage 10, approximately 18 h prior to floral open-
ing.
Anthesis
occurs at stage 12. The duration of the maturation stage is
about 12 h. The
post-maturation stage
encompasses all stages that occur
after anthesis. It lasts as long as the flower is receptive to pollination. During
this time, nectar flow continues; the flow is strongest at the beginning and
weakens the longer the flower remains open. This stage can sometimes last
6-8 days if the flower is not pollinated.
The nectaries of LxS8 ornamental tobacco plants produce a nectar com-
posed of specific compounds (Table 1). Chief among these are the sugars
glucose, fructose, and sucrose, although specific amino acids, vitamin organic
acids, proteins, and reactive oxygen species are all significant components of
this nectar (Carter et al., 1999, 2006; Carter & Thornburg, 2000, 2004a, b, c).
3
DEVELOPMENTAL PROCESSES
When examining the development of nectaries in ornamental tobacco, it is
clear that there are a number of changes that occur as the nectary matures.
The two most obvious changes relate to the size of the nectary and its change
in colour (Fig. 1). Although this is difficult to see in the figure, by stage 2
