Study of the watering frequency of young seedlings of Acacia nilotica (L.) Willd. ex Del. (Mimosaceae) in the nursery on recovery after field transplanting in Maroua, Cameroon

Abstract

The environmental and social impact of deforestation can be partly offset by the planting of local woody species such as Acacia nilotica, but unless sown directly into their final positions, sooner or later, young seedlings have to be set out in the soil. This a crucial stage when the plants are vulnerable to drought stress. Therefore, this work aims at studying the effect of the induction of water stress in the nursery on the behavior of Acacia nilotica seedling after transplanting. The experimental design was a one-factor randomized block (watering frequencies). The blocks (03) constitute the repetitions. The five (05) watering frequency levels was F0 (control), F1, F2, F3, F4 and F5 respectively for twice-daily watering at field capacity after 12h, 24h, 48h, 72h, 96h and 120h. The stress applications took place seven (07) days after germination for ninety (90) days and transplant into the natural environment. After transplanting (60 days), the rate of increased in height and collar diameter as well as the survival rate increase with the stress level of the seedlings in the nursery. It emerges from this work that the more the level of stress increased, the more the aerial growth of the seedlings was reduced, unlike the root part. The aerial biomass went from 10.23g (F0) to 9.22g (F3) and to 8.67g for F5, ie a respective reduction rate of about 10 and 16%. On the other hand, the root biomass increased from 3.07g (F0) to 4.31g (F3) and 5.56g for F5, that is to say an increase rate of about 40 and 81% respectively. Biochemical analysis revealed that with the exception of chlorophylls (Chl T: 7.27 mg/g FM for F0 to 3.38 mg/g FM for F5), the other measured elements (Proline: 5.27% (F0) to 27.84% to F5; Polyphenol: 6.25% (F0) to 7.47% to F5, Soluble sugar: 15.17% (F0) to 36.66% to F5 and total Proteins: 24.84% (F0) to 28.64% to F5) increase with the level of stress but decrease at the highest level. Subjecting young seedlings to water stress in the nursery allowed them to develop mechanisms for acclimatization to water stress. These results could be useful to the various reforestation programs for the production of vigorous seedlings.