Paclobutrazol Application Favors Yield Improvement of Maize Under Semiarid Regions by Delaying Leaf Senescence and Regulating Photosynthetic Capacity and Antioxidant System During Grain-Filling Stage

Abstract

In the present study, we examined the potential role of paclobutrazol in delaying leaf senescence, in causing changes in the activities of antioxidants, and in the maintenance of photosynthetic activity during the senescence process, and, therefore, on the grain yield of maize under semiarid field conditions. Maize seeds were pretreated with 0 (CK), 200 (PS1), 300 (PS2), and 400 (PS3) mg paclobutrazol L−1. Our results indicated that elevated levels of reactive oxygen species (ROS) and higher accumulation of malondialdehyde (MDA) contents were positively associated with accelerated leaf senescence during the grain-filling periods. The leaf senescence resulted in the disintegration of the photosynthetic pigments and reduced the net photosynthetic rate after silking. However, the resultant ROS burst (O2− and H2O2) was lessened and the leaf senescence and chlorophyll degradation were evidently inhibited in leaves of paclobutrazol-treated maize plants, which was strongly linked with upregulated activities of antioxidant enzymes in treated plants. The enhanced chlorophyll contents and availability of a greater photosynthetic active green leaf area during the grain filling period facilitated the maintenance of higher photosynthetic rate, and light-harvesting efficiency of photosynthesis associated with photosystem II (PSII) resulted in higher kernel number ear−1 and thousand kernel weights, and thus increased the final grain yield. The average maize grain yield was increased by 18.8% to 55.6% in paclobutrazol treatments, compared to untreated control. Among the various paclobutrazol treatments, PS2 (300 mg L−1) treatment showed the most promising effects on enhancing the activities of antioxidative enzymes, delaying leaf senescence and improving the yield of maize. Thus, understanding this effect of paclobutrazol on delaying leaf senescence introduces new possibilities for facilitating yield improvement of maize under semiarid conditions.

Zinc and Paclobutrazol Mediated Regulation of Growth, Upregulating Antioxidant Aptitude and Plant Productivity of Pea Plants under Salinity

“…The stimulating effect of Zn under normal or stress conditions is dedicated to accelerating the photosynthesis processes and accelerated photoassimilation translocation into the plant [ 19 , 28 , 29 ]. Additionally, Zn induces indole acetic acid (IAA) biosynthesis, accelerating cell division and enlargement, and eliminating ROS [ 14 , 15 , 21 ]. The encouragement role of PBZ on plant growth could be related to its effect on increasing internal carbon dioxide concentration and leaf thickness, enhancing plant cell water retention, and increasing water use efficiency [ 21 ].…”

“…Additionally, Zn induces indole acetic acid (IAA) biosynthesis, accelerating cell division and enlargement, and eliminating ROS [ 14 , 15 , 21 ]. The encouragement role of PBZ on plant growth could be related to its effect on increasing internal carbon dioxide concentration and leaf thickness, enhancing plant cell water retention, and increasing water use efficiency [ 21 ].…”

“…Zinc probably keeps chlorophyll assimilation through the protection of the sulphydryl group and improved Mg uptake [ 34 , 35 , 36 ]. Paclobutrazol application has been documented to boost chlorophyll under normal or stress conditions [ 21 ]. This increment may be ascribed to raise the cytokinin concentration [ 14 ] that consecutively improved chloroplast differentiation and chlorophyll assimilation, preventing chlorophyll degradation [ 37 ].…”

“…Ascorbic acid (AsA) is a small water-soluble powerful antioxidant in several plants that accumulate about 2–25 mM under normal conditions [ 41 ]. Under saline conditions, and Zn [ 3 ] and PBZ [ 21 ] availability, plants accumulate more AsA in their tissues. Ascorbic acid acts directly to neutralize ROS and contributes to the cellular homeostasis through multiple strategies [ 41 , 42 ]: (1) AsA can eradicate numerous ROS molecules and α-tocopherol, thereby protecting cellular biomembranes; (2) AsA reduces the production of H 2 O 2 in the stroma; and (3) AsA acts in an imperative role in plant biochemical pathways and developmental processes, including the regulation of cell division and expansion.…”

“…Phytohormones like triazole compounds (plant multi-stress protectants) play an imperative function in regulating various growth and behavioral processes under normal or stressful conditions [ 20 ]. Paclobutrazol (PBZ) is now extensively used in agriculture for regulating plant development and increasing crop yield under normal or stress conditions [ 14 , 21 ]. The most prominent and likely hypothesis on increasing plant production and stress tolerance induced by PBZ has been attributed to it sustaining the endogenous cytokinin concentration, maintaining water status, improving nutrient uptake and carbohydrate synthesis, improving chlorophyll biosynthesis, and promoting antioxidant capacity [ 20 , 21 ].…”