Carbon allocation in banana plants – the effects of drought stress and suckers

Banana is a perennial crop that propagates vegetatively through the formation of so-called suckers. Suckers are photosynthetically active, but remain connected to the mother plant. Their initial formation is driven by a carbon flux from the mother plant, but it is not known to which extent this flux persists once the sucker develops further. Drought stress is one of the most important limitations to banana production. Nonetheless, the effect of drought stress on the integrated system of mother plant and suckers remains unknown. In a greenhouse experiment, we aimed to quantify carbon fluxes in banana plants and assess the effects of drought stress and suckers on carbon allocation. We labeled banana mother plants with and without suckers with ¹³CO₂, while the suckers were sealed gas tight. An optimal and suboptimal watering treatment were applied. The label was then traced in the phloem sap, in the leaves of mother plant and sucker and in the underground corm for a period of two weeks. Most of the label was either lost through respiration (37.5 ± 3.0 %) or allocated to the mother plant leaves (35.6 ± 2.2 %). Plants without suckers did not invest more in the growing mother plant, but instead, had higher respiratory losses. In plants with suckers, 3.1 ± 0.7 % of ¹³C assimilated by the mother plant was translocated to the sucker. Drought stress reduced the allocation to the sucker. On average, 5.8 ± 0.4 % of the label ended up in the corm, which connects all leaves and plant parts but also serves as a storage organ, by accumulating starch. Both drought stress and sucker presence increased overall translocation to the corm. Starch accumulation also increased under drought stress or in the presence of a sucker. However, when drought stress and a sucker were both present, starch accumulation was severely reduced. Finally, 17.2 ± 1.1 % of the label ended up in the wrapped leaf sheaths of the mother plant, that form the structurally important pseudostem. The pseudostem as well serves as a source of carbohydrates for future fruit and sucker development. Sucker presence increased carbon allocation to the pseudostem. In conclusion, it seems that suckers and drought stress affected carbon dynamics in banana plants similarly, namely by increasing carbon allocation to storage tissues. Their combination, however, resulted in an imbalance between carbon supply and demand and hence the plants’ investment in sucker growth, as well as in long-term storage were reduced.