Yl. Ruan et al., THE COMPOSITION OF APOPLAST FLUID RECOVERED FROM INTACT DEVELOPING TOMATO FRUIT, Australian journal of plant physiology, 23(1), 1996, pp. 9-13
A pressure dehydration technique for recovering sap from the apoplast
of the pericarp tissue of developing tomato fruit has recently been de
veloped. Samples of this sap from two cultivars have now been analysed
for sugars, amino acids, organic acids, ammonia and inorganic ions. T
he measured solutes accounted for 92 and 97% of the osmolality of the
apoplast sap from the two cultivars. The osmotic potential of the apop
last samples was similar in the two cultivars, and the apoplast sample
s were distinctly different in osmolality and in composition from samp
les of the bulk sap obtained after thawing frozen tissue. Hexoses and
inorganic compounds, principally potassium and chloride, accounted for
75% of the osmotic potential of the apoplast samples. There is little
prior information on the composition of the apoplast in fruit. The im
pact of this new knowledge is discussed in relation to the uptake of s
olutes into fruit cells, the partitioning of solutes between apoplast
and symplast, and the ionic environment of the cell wall and wall-boun
d enzymes.