INVESTIGATIONS ON THE INTERCELLULAR SYSTE M OF APPLE FRUIT BY DIGITALIMAGE-PROCESSING METHODS

The intercellular system of plants is needed for gas exchange of the c ells, and it forms an internal atmosphere. The investigations aimed to evaluate the intercellular system of apple fruits quantitatively and to find out possible parameters affecting it. Therefore, plastic embed ded material of hypodermis, cortex, and core area was sectioned at 5 m um, stained with hematoxylin, and processed to permanent slides. The s amples were investigated quantitatively using a digital image processi ng system for the volume percentage of the intercellular spaces. It wa s shown that within the fruit the intercellular volume increases from below the skin (hypodermis), reaching its maximum in the cortex and de clining to the core area. The cortex, which comprises the major part o f the fruit, possesses a rather uniform intercellular volume. The comp arison of small and large fruits of the same variety showed positive c orrelations between fruit size and intercellular volume of all varieti es investigated. Therefore, increasing fruit sizes result in a higher intercellular volume. higher intercellular volume compared to varietie s with small fruits. The growth rate of the intercellular volume was h ighest in the equatorial plane of the cortex as the increase in fruit size is highest in this area. The comparison of 9 varieties showed tha t the intercellular volume is specific for a given variety, which is m ost pronounced in the hypodermis area, decreasing to the cortex and co re area. A negative correlation was found between specific weight of a variety and the intercellular volume. Thus, varieties with a high spe cific weight have a lower gas content in their fruits and vice versa. Development of the intercellular volume during the vegetation period a nd storage was followed in five varieties. It was shown that the inter cellular volume increases in accordance with fruit growth, forming an S-shaped curve. Within the fruit the cortex increases most intensively . During storage intercellular volume increases continuously, especial ly in the cortex area.