Abstract
This paper investigated changes in growth and carbohydrate content of shoots and root systems in response to source-sink manipulation in field-grown coffee trees. The source-sink manipulations were carried out using manual de-fruiting. Two plots of trees were established: in one group, the fruit was left on the tree, while in the second group all fruits were removed manually. Similar results were obtained for coffee trees with and without fruit in terms of height, stem and skirt diameter and branch lengths. A biochemical evaluation of the roots showed that no differences were found between the levels of carbohydrates. In the leaves, levels of soluble sugars and reducing sugars were higher in plants with fruit. The starch concentration in leaves and roots did not vary between the plots. Root length density did not vary between plants with and without fruit in the 0 - 0.4 m soil layer. However, plants without fruit had a higher root length density than plants with a full fruit load. These results contrast with results published by others on source-sink relationships of coffee plants. The joint data analysis shows that young trees, with a moderate fruit load, and with good nutritional and health status, produce carbohydrates in sufficient quantities to maintain vegetative and reproductive growth, without harming root system growth.
Highlights
The growth and development of plants involves a complex relationship between shoots and the root system
Our data shows that the presence of fruit on the plants limited the mobilization of assimilates to the root system since, in this organ, the levels of soluble sugars were lower than those plants without fruit (Figure 3)
The joint data analysis shows that young trees, with moderate fruit load, and with good nutritional and health status produce carbohydrates in quantities sufficient to maintain the vegetative and reproductive growth, without harming the growth of the root system
Summary
The growth and development of plants involves a complex relationship between shoots and the root system. The assimilated compounds produced by the leaves during the process of photosynthesis are translocated throughout the plant to satisfy demand for the carbon and energy that will be responsible for the formation of new tissues (TAIZ; ZEIGER, 2006). According to their ability to export and import photoassimilates, plant organs can be classified as source and sink, respectively (WUBS et al, 2009). Cannel (1976) studied the partitioning of assimilates between leaves and fruits, and concluded that a leaf area of 20 cm is required to fulfill the requirements of each coffee fruit growth.
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