Cell expansion as an important driver of fruit growth
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Fruit growth and development undergoes four major stages. The first phase involves floral initiation, carpel formation and preanthesis cell division and ends at anthesis. The second phase starts with flower pollination followed by fertilization of ovules and fruit set which marks the restart of cell division. At this early stage, cell division is the main process by which fruits increase in size. This wave of cell division continues for approximately 2 weeks in the tomato pericarp but in some genotypes, it is still significant 25 days after anthesis. However, the duration of cell division is much longer in the epidermis, where it continues shortly after the fruit has attained its full size. The third phase of fruit development is characterized by cell expansion, leading to spectacular increase in cell size and consequently fruit size. This phase involves a great import of water and sucrose, accumulation of starch and its hydrolysis into fructose and sucrose. Despite this observation in cell size increment during the third phase,past research has only reported a positive correlation between cell number and fruit size and no correlation between volume and fruit size. The objective of this research was to devise methods of cell size estimation that reveal the positive correlation between cell volume and fruit size i.e. assume different cell shapes and methods of obtaining average cell volume. The research was carried out using secondary data from an earlier research and the data was collected on the the following parameters, cell largest length and largest width and then this was subjected to the different formulae according to the different assumptions made. Results obtained from the research only showed a positive correlation between cell volume and fruit size at 24 days after anthesis and not at breaker stage regardless the cell shape assumption. Secondly, cells assumed sphere showed a stronger correlation between cell volume and fruit size compared to the other assumptions. It also showed that it is better for the average cell volume to be obtained from a rectangle of cells than from individual cells.