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<p>The current climate change scenario with high temperatures and severe droughts threatens açai palm production in the Amazon. High sensitivity to drought reduces seedling production in nurseries and drastically hinders the plantings renewal in the field. As an alternative to increase plant tolerance to drought and reduce mortality, biostimulants based on growth-promoting rhizobacteria or seaweed extracts have been used. However, the combined use of different biostimulants to increase drought tolerance and help with water recovery has not yet been tested. The study objective was to evaluate the separate and combined effect of the biostimulants <i>Bacillus subtilis</i> (BS) and seaweed extract (SE) on physiological and biochemistry changes caused by water deficit (WD) and to analyze their rehydration capacity in açai palm seedlings. The experiment was carried out in a greenhouse with the biostimulants applied separately as BS and SE or combined as BS + SE in açaí seedlings. After 7&#xa0;days of WD, seedlings biostimulated with SE increased net CO<sub>2</sub> assimilation rate (<i>A</i>), stomatal conductance (<i>g</i><sub>s</sub>), transpiration (<i>E</i>) and carboxylation efficiency (<i>A</i>/<i>C</i><sub>i</sub>), respectively, by 76%, 100%, 39% and 75%, compared to the control treatment. After 14&#xa0;days of WD, plants with SE and BS + SE increased by 71% and 35% in <i>A</i>; 100% and 63% in <i>g</i><sub>s</sub>. At 14&#xa0;days of WD, the MDA concentration of control plants was higher than biostimulated plants. Plants treated with SE showed higher enzymatic activity for superoxide dismutase (SOD) and catalase (CAT) and with BS + SE for SOD, CAT and ascorbate peroxidase (APX). After rehydration, all biostimulated plants had statistically higher averages of net CO<sub>2</sub> assimilation rate (A) and carboxylation efficiency (<i>A</i>/<i>C</i><sub>i</sub>). Plants with SE increased 101% <i>A</i> and 100% <i>A</i>/<i>C</i>i. Açai palm seedlings biostimulated with BS, SE and BS + SE accumulated more proline during rehydration. The BS + SE treatment showed greater activity for the SOD, CAT and APX, higher than WD control. BS and SE or BS + SE can attenuate changes in water status, gas exchange and antioxidant responses up to moderate levels of drought, while at more severe levels only SE and BS + SE were able to activate osmoregulation and photosynthetic apparatus protection, in addition to improving physiological plasticity after rehydration. SE or BS + SE can be an efficient alternative to reduce losses in nurseries and contribute to a clean technology that can improve the adaptation of açaí palm to global climate change.</p>

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Combined application of Bacillus subtilis and seaweed extracts in açaí palm seedlings subjected to water deficit and recovery

  • 期刊论文

  • 发表日期：

    2025年6月11日

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  • Maria Carolina Sarto Fernandes Rodrigues,
  • Maria Luiza Brito Brito,
  • Verônica Daniely Pereira Paz da Silva,
  • Danielle Pereira Mendonça,
  • Maria Joselina Gomes Ribeiro,
  • Gisele Barata da Silva,
  • Gledson Luiz Salgado de Castro

摘要

The current climate change scenario with high temperatures and severe droughts threatens açai palm production in the Amazon. High sensitivity to drought reduces seedling production in nurseries and drastically hinders the plantings renewal in the field. As an alternative to increase plant tolerance to drought and reduce mortality, biostimulants based on growth-promoting rhizobacteria or seaweed extracts have been used. However, the combined use of different biostimulants to increase drought tolerance and help with water recovery has not yet been tested. The study objective was to evaluate the separate and combined effect of the biostimulants Bacillus subtilis (BS) and seaweed extract (SE) on physiological and biochemistry changes caused by water deficit (WD) and to analyze their rehydration capacity in açai palm seedlings. The experiment was carried out in a greenhouse with the biostimulants applied separately as BS and SE or combined as BS + SE in açaí seedlings. After 7 days of WD, seedlings biostimulated with SE increased net CO2 assimilation rate (A), stomatal conductance (gs), transpiration (E) and carboxylation efficiency (A/Ci), respectively, by 76%, 100%, 39% and 75%, compared to the control treatment. After 14 days of WD, plants with SE and BS + SE increased by 71% and 35% in A; 100% and 63% in gs. At 14 days of WD, the MDA concentration of control plants was higher than biostimulated plants. Plants treated with SE showed higher enzymatic activity for superoxide dismutase (SOD) and catalase (CAT) and with BS + SE for SOD, CAT and ascorbate peroxidase (APX). After rehydration, all biostimulated plants had statistically higher averages of net CO2 assimilation rate (A) and carboxylation efficiency (A/Ci). Plants with SE increased 101% A and 100% A/Ci. Açai palm seedlings biostimulated with BS, SE and BS + SE accumulated more proline during rehydration. The BS + SE treatment showed greater activity for the SOD, CAT and APX, higher than WD control. BS and SE or BS + SE can attenuate changes in water status, gas exchange and antioxidant responses up to moderate levels of drought, while at more severe levels only SE and BS + SE were able to activate osmoregulation and photosynthetic apparatus protection, in addition to improving physiological plasticity after rehydration. SE or BS + SE can be an efficient alternative to reduce losses in nurseries and contribute to a clean technology that can improve the adaptation of açaí palm to global climate change.