Growth and development of tomato fruitsin vivo andin vitro

Abstract

Abstract. Tomato (Lycopersicon esculentum Mill.) fruits of the male sterile cultivar Pearson (MS35 BC4,61) were transferred to in vitro culture during the cell division period. Fruits grown in vivo and in vitro were compared throughout their development according to various growth parameters: fresh and dry weight, cell number, cell diameter, and DNA and total protein content. In all cases, the values pertaining to fruits grown in vitro were significantly lower than their in vivo counterparts. The final fresh weight of fruits transferred to culture 2, 5, or 10 days after pollination was only 0.7, 1.2, and 3.4%, respectively, of that of plant-grown fruits. The results indicate that the reduced fruit size in vitro is related to the reduction in both cell number and cell size. It is interesting to note that the DNA content per cell increased 15-fold during the growth of the plantgrown fruits while this accumulation was only between 2-and 3-fold in all the cultured fruits. The time to first colour appearance of fruits cultured 2,5, or 10 days after pollination was 196, 132 and 85%, respectively, of that of plant-grown fruits.

The possible involvement of polyamines in the development of tomato fruits in vitro

“…The older the fruit when transferred to culture (towards the end of the cell division period), the greater is its final size [18]. Tomato fruits were therefore transferred to culture on day 2, 5, or 10 and compared at various time intervals with their in vivo counterparts with respect to ODC and ADC activity and the endogenous level of free putrescine, spermidine, and spermine.…”

“…We will refer to fruit age as starting from the moment of pollination. The fruits were allowed to develop on the plant or were transferred to culture [18]. Those in vitro fruits used in the determination of the endogenous level of free polyamines and of enzyme activity were transferred to culture on day 2, 5 or 10 (during the cell division period) while those used to determine the effect of exogenous putrescine were all transferred on day 2.…”

“…The cell number of fruits was determined with a haemocytometer on macerated pericarp tissue [10,18]. The dry weight was determined after drying tissue samples in an oven at 70°C for 72 h. The cell diameter was determined microscopically in thin slices of fruit pericarp tissue with an ocular micrometer.…”

“…It was previously shown by Teitel et al [ 18] that the smaller size of tomato fruits grown in vitro can be attributed to disruption of the processes of cell division and cell growth. Unlike tomato fruits in rive, where the DNA content increases several-fold during development [5,14,18], DNA accumulation in fruits in vitro was severely reduced [18].…”

“…Cellular DNA content has been shown to be positively correlated with cell size in tomato fruits [5,14,18]. Since the effect of polyamines on celt division may be due to their essential role in DNA replication [2] and synthesis of macromolecules such as RNA and proteins [13] that are essential for cell growth, polyamines may also influence overall cell growth in tomato fruits [5,14,18].…”