Research on tropical yeast ecology-1:-DETECTION OF REDUCING SUGARS FROM FLORAL NECTAR

Dr. Nandakumar Kamat nkamat at
Wed Aug 18 10:35:50 EST 2004

We are posting a copy of our paper for people interested in looking for
saccharophilic yeasts in floral nectar. Please acknowledge this source if
you use this technique/refer to it.
-Dr. Nandkumar Kamat
Da silva Nikita and Kamat Nandkumar
Department of Botany, Goa University, Taleigao, Goa, India
E-mail:-astronix2003 at
We report here a simple rapid reproducible microchemical  slide test using
Benedict’s reagent for detection of reducing sugars in floral nectar.
This work was necessitated because of our interest in studying ecological
and microbiological aspects of floral nectars containing reducing sugars
such as Glucose, Fructose and Sucrose  (Gillespie and Henwood, 1994).
Except in a few species, generally many flowers produce negligible
quantities of nectar. These quantities are difficult to sample and
estimate so it has been felt that some rapid tests may be necessary to get
an idea of the chemical composition of microquantities of nectar. An
estimate of presence or absence of sugars in nectar provides important
clues for high frequency isolation of saccharophilic nectar inhabitating
microorganisms. The present techniques such as HPLC or IR spectroscopy
require time consuming and sophisticated methods for detection of sugars
in nectar fluid (Ortiz et. al. 2003).  We have resolved this problem by a
simple modification of reducing sugar estimation technique using
Benedict’s reagent at a micro level. We use standard microscope slides for
this test. Small drops of nectar fluid, extracted from flowers using a
microcapillary are placed on a clean slide and mixed with a drop or two of
Benedict’s reagent. The slide is then heated gently till a permanent
colouration is observed. The intensity of the colour is noted. This gives
an idea of the concentration of sugars. We maintained control slides using
pure solutions of Glucose and Fructose treated in the same manner. A brick
red precipitate on the slide indicates the presence of glucose. Generally
the presence of Fructose is masked by this reaction so we assume that both
 Glucose and Fructose are present when a brick red or orange-red
colouration is found. Absence of brick red, orange colour after heating
the slide indicates absence of any sugars in the nectar sample.  Using
this test positive and reproducible results were obtained with micro
quantities of nectar from Thevitia peruviana (Pers.) K. Schum.  and
Momardica dioica Roxb. ex Willd. The positive tests direct us in
microbiological sampling.
Work is in progress for further improvement of this technique to give semi
quantitative estimates of sugar concentration in floral nectar. These
results would be separately published elsewhere.
Gillespie L.H. and Henwood J.M. (1994). Temporal changes of floral
nectar-sugar composition in Polyscias sambucifolia (sieb. Ex DC.) Harms
(Araliaceae), ann. Of Bot. 74:227-231.
Ortiz, C.M. Castro, I.P. Portilla, L.B.  Aranda, P.D. Arizmendi, Mdel, C.
Carbohydrate analysis of floral nectar using infra red.Phytochem Anal.
14(5): 319-24

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