Biology Reference
In-Depth Information
Table 3.
Advantages and disadvantages of photosynthetic and non-photosynthetic nectaries.
The same volume of nectary parenchyma has a higher nectar production rate when nectar is
produced by hydrolysis of stored starch than by direct photosynthesis.
Advantages
Disadvantages
Nectar can be produced for days
Nectar carbohydrates are produced
and presented for consumption only
in the day if starch is hydrolysed only
at night
or months as in extrafloral
nectaries
Nectar carbohydrates at least
partly originate from photosynthe-
sis by nectary parenchyma
Nectar production rate is low and
proportional to nectary parenchyma
volume
Nectar carbohydrates are pro-
duced close to the presentation
site
Nectar sugar concentration rarely
reaches high values
Nectary may continue photosyn-
thesis when nectar production is
over, to the benefit of developing
fruit
The nectary can be a portal for
pathogens because of long nectar
production*
Nectar removal by insects may
lead to further nectar production
Nectar may be exposed to con-
sumers at any time of day
Nectar is derived from photosynthe-
sis by green floral parts, bracts or
leaves close to the flower which are
affected by environment
Large amounts of nectar can be
produced in a short period of time
Nectaries commonly fall after nectar
secretion and any unconsumed nectar
has been reabsorbed
It is possible to produce nectar
with a high sugar concentration
No further nectar can be produced
after consumption
Reabsorption of unconsumed
nectar may occur by the nectary
itself and empty amyloplasts may
temporarily store nectar carbohy-
drates
*The presence of antimicrobial proteins avoids this disadvantage.
