Abstract
Humic substances (HS) are the most important natural biostimulant of plants. However, the relationship between their structure and biological activity in plants is still not well recognized. The objective of this paper was to assess the influence of molecular fractions of humic acids (HA) (HA < 30 kDa and HA > 30 kDa) on reducing negative effects of drought stress in soybean (Glycine max (L.) Merr.) seedlings of Progres and Nawiko cultivars. Drought stress was induced in laboratory conditions by the addition of polyethylene glycol 6000 (PEG 6000) to make a water potential of −0.5 MPa. HA were extracted according to the International Humic Substances Society procedure, and then were separated into two molecular fractions by membrane filtration. The following physiological and biometric parameters were determined: chlorophyll content, photosynthesis activity, electrical conductivity, fresh and dry mass of overground and roots, and plant length. The enzyme activity and ion contents were also measured. Differences in response to drought stress with the addition of HA < 30 kDa and HA > 30 kDa or not to the Hoagland’s solution were observed among studied cultivars. Drought stress caused a decrease in the most physiological parameters and increase in peroxidase activity in the case of both studied cultivars. However, the results of biometric measurements showed that the Progres cultivar appears to have better tolerance to drought stress. The significant influence of water deficit on most macroelement content in dry matter leaves of both studied cultivars was not observed, while its effect on microelement uptake by soybean plants was concluded. In the case of the Progres cultivar, the results showed a significant decrease in microelement content in the dry matter of leaves, whereas in the leaves of Nawiko cultivar there was a significant increase. The influence of HA > 30 kDa and HA < 30 KDa fractions on physiological features of both studied cultivars was varied. HA > 30 kDa fraction better up-regulated the antioxidant defense system. Unfortunately, no effect of either HA fraction on the macro- and micronutrients uptake system of both studied cultivars was observed.
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Claims 10
Claim · model-written summary
Cultivars differed in their response to drought and humic acid fractions.
- Taxon
- Soybean
Glycine maxt0 - Treatment
- HA < 30 kDa and HA > 30 kDae0
- Outcome
- response to drought stresse0
- Direction
- Differencese0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Differences in response to drought stress with the addition of HA < 30 kDa and HA > 30 kDa or not to the Hoagland’s solution were observed among studied cultivars.”
t0“Soybean”
Claim · model-written summary
Drought decreased most physiological parameters in both cultivars.
- Taxon
- SoybeanGlycine maxt0
- Treatment
- Drought stresse0
- Outcome
- physiological parameterse0
- Direction
- decreasee0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Drought stress caused a decrease in the most physiological parameters and increase in peroxidase activity in the case of both studied cultivars.”
t0“Soybean”
Claim · model-written summary
Drought increased peroxidase activity in both cultivars.
- Taxon
- SoybeanGlycine maxt0
- Treatment
- Drought stresse0
- Outcome
- peroxidase activitye0
- Direction
- increasee0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Drought stress caused a decrease in the most physiological parameters and increase in peroxidase activity in the case of both studied cultivars.”
t0“Soybean”
Claim · model-written summary
Progres appeared more tolerant of drought.
- Taxon
- SoybeanGlycine maxt0
- Material
- Progrese0
- Outcome
- tolerance to drought stresse0
- Direction
- bettere0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“the Progres cultivar appears to have better tolerance to drought stress”
t0“Soybean”
Claim · model-written summary
Water deficit had no significant effect on most leaf macroelement content.
- Taxon
- SoybeanGlycine maxt0
- Organ / stage
- leavese0
- Treatment
- water deficite0
- Outcome
- most macroelement contente0
- Direction
- not observede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The significant influence of water deficit on most macroelement content in dry matter leaves of both studied cultivars was not observed”
t0“Soybean”
Claim · model-written summary
Water deficit reduced leaf microelement content in Progres.
- Taxon
- SoybeanGlycine maxt0
- Material
- Progrese0
- Organ / stage
- leavese0
- Outcome
- microelement contente0
- Direction
- decreasee0
Not reportedTreatmentComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“In the case of the Progres cultivar, the results showed a significant decrease in microelement content in the dry matter of leaves”
t0“Soybean”
Claim · model-written summary
Water deficit increased leaf microelement content in Nawiko.
- Taxon
- SoybeanGlycine maxt0
- Material
- Nawikoe0
- Organ / stage
- leavese0
- Outcome
- microelement contente0
- Direction
- increasee0
Not reportedTreatmentComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“In the case of the Progres cultivar, the results showed a significant decrease in microelement content in the dry matter of leaves, whereas in the leaves of Nawiko cultivar there was a significant increase”
t0“Soybean”
Claim · model-written summary
Humic acid fractions had varied effects on physiological features.
- Taxon
- SoybeanGlycine maxt0
- Treatment
- HA > 30 kDa and HA < 30 KDa fractionse0
- Outcome
- physiological featurese0
- Direction
- variede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The influence of HA > 30 kDa and HA < 30 KDa fractions on physiological features of both studied cultivars was varied.”
t0“Soybean”
Claim · model-written summary
The larger humic acid fraction better up-regulated antioxidant defense.
- Taxon
- SoybeanGlycine maxt0
- Treatment
- HA > 30 kDa fractione0
- Outcome
- antioxidant defense systeme0
- Direction
- up-regulatede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“HA > 30 kDa fraction better up-regulated the antioxidant defense system.”
t0“Soybean”
Claim · model-written summary
Neither humic acid fraction affected macro- or micronutrient uptake.
- Taxon
- SoybeanGlycine maxt0
- Treatment
- either HA fractione0
- Outcome
- macro- and micronutrients uptake systeme0
- Direction
- no effecte0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“no effect of either HA fraction on the macro- and micronutrients uptake system of both studied cultivars was observed.”
t0“Soybean”
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