Effects of Humic Substances and Mycorrhizal Fungi on Drought-Stressed Cactus: Focus on Growth, Physiology, and Biochemistry

Abstract

Utilizing water resources rationally has become critical due to the expected increase in water scarcity. Cacti are capable of surviving with minimal water requirements and in poor soils. Despite being highly drought-resistant, cacti still faces limitations in realizing its full potential under drought-stress conditions. To this end, we investigated the interactive effect of humic substances (Hs) and arbuscular mycorrhizal fungi (AMF) on cactus plants under drought stress. In the study, a cactus pot experiment had three irrigation levels (W1: no irrigation, W2: 15% of field capacity, and W3: 30% of field capacity) and two biostimulants (Hs soil amendment and AMF inoculation), applied alone or combined. The findings show that the W1 and W2 regimes affected cactus performance. However, Hs and/or AMF significantly improved growth. Our results revealed that drought increased the generation of reactive oxygen species. However, Hs and/or AMF application improved nutrient uptake and increased anthocyanin content and free amino acids. Furthermore, the soil’s organic matter, phosphorus, nitrogen, and potassium contents were improved by the application of these biostimulants. Altogether, using Hs alone or in combination with AMF can be an effective and sustainable approach to enhance the tolerance of cactus plants to drought conditions, while also improving the soil quality.

Integration of Horse Manure Vermicompost Doses and Arbuscular Mycorrhizal Fungi to Improve Fruit Quality, and Soil Fertility in Tomato Field Facing Drought Stress

“…Figure 1 reveals a significant increase in total soluble sugar (TSS) and total acidity (TAC) accumulation in tomato fruits growing under DS conditions; however, protein content was reduced under the same conditions, in comparison with WW watered plants. Furthermore, AMF, C1, C2, AMF+C1, and AMF+C2 plants increased TSS accumulation (24,13,22,49, and 42%, respectively), TAC (6,11,16,9, and 15%, respectively) and protein content (49,69,81,87, and 65%, respectively), compared with control plants tested under DS conditions. In WW conditions, TSS and protein content increased substantially with the application of biostimulants, with a particularly marked increase recorded with AMF+C1 for TSS contents, and C1 for protein.…”

“…This is crucial for maintaining turgor pressure and metabolic activities in developing fruits, resulting in improved growth outcomes [ 51 , 52 ]. Furthermore, fungi contribute to the absorption and facilitation of nutrient uptake, particularly by enhancing the uptake of P in plants [ 24 ]. Phosphorus is vital for cellular energy transfer, photosynthesis, and the synthesis of nucleic acids, all of which contribute to increased fruit size and biomass [ 53 ].…”

“…Carotenoids and lycopene, known for their bright pigmentation in tomatoes, play an important role beyond aesthetic appearance [ 61 ]. Previous studies have shown that these compounds have strong antioxidant properties, effectively quenching singlet oxygen and various other volatile oxygen species, thus preventing potential damage to cellular components caused by water stress [ 24 , 63 , 64 ].…”

“…AMF regulate plant growth and development by forming extra-radical mycelium around the roots, which are inaccessible to roots or even root hairs, enabling the interchange of nutrients and water for carbon sources such as sugars and lipids [ 20 , 21 ]. Plants inoculated with AMF, such as Festuca ovina , Opuntia ficus-indica , and Zea mays , enhance plant growth and improve the absorption of nutrients, especially nitrogen (N) and phosphorus (P), demonstrating the usefulness of AMF to various plant species [ 22 , 23 , 24 ]. Recent research suggests that mycorrhizal fungi do more than just aid nutrient uptake.…”

“…Recent research suggests that mycorrhizal fungi do more than just aid nutrient uptake. They also play a major role in stimulating microbial and enzymatic activity, enhancing photosynthesis, and increasing water uptake and flexibility in the face of abiotic and biotic stresses, ultimately leading to increased yields [ 24 , 25 , 26 , 27 ].…”