Maize harvest index and water use efficiency can be improved by inhibition of gibberellin biosynthesis

Abstract

Possibilities to improve maize harvest index and nutrient utilization efficiency by application of plant growth regulators were investigated. In container experiments, the effects of different growth regulators on the development of the maize (Zea mays L.) cultivars Pioneer 3906 and Fabregas were tested. Paclobutrazol (PAC) and chlorocholine chloride (CCC), two inhibitors of gibberellin biosynthesis, as well as gibberellic acid (GA3) were applied at growth stage V5. Three weeks after application of PAC, shoot growth of both maize cultivars was strongly affected with a significant decrease in plant height in the PAC treatment by 44% and 36% for Pioneer 3906 and Fabregas, respectively. The growth‐retarded plants had higher leaf areas and reduced transpiration rates. The higher shoot growth after GA3 application was accompanied by a reduction in leaf area and an increase in transpiration rate during 1 week before anthesis. CCC treatment showed no significant effects on plant height, leaf area and transpiration rate. The PAC‐treated cultivar Pioneer 3906 produced several cobs per plant, which were mainly barren at maturity. However, PAC application to Fabregas resulted in just one cob per plant with good kernel development and a grain yield, which was not significantly reduced in comparison with the control. With this similar grain yield in combination with a straw yield decrease of 32%, the harvest index was significantly improved by 12%. In addition, with PAC‐treated Fabregas plants, a 19% increased water use efficiency of the grain (WUEgrain) during the critical period of kernel setting was achieved. In this maize cultivar, CCC application also improved harvest index by 5%, but no effect on WUEgrain occurred. GA3 treatment decreased harvest index of both maize cultivars, and it either reduced WUEgrain (Pioneer 3906) or showed no effect (Fabregas). Utilization efficiencies of N, P and K were not increased with growth regulator application, even in the PAC‐treated Fabregas plants with a significantly improved allocation of assimilates to the grain, mirrored by the higher harvest index. The results indicate that fertilizer applications must be adjusted to the reduced demand of growth‐retarded plants, most likely leading to higher nutrient utilization efficiencies.

Water‐use efficiency of maize may be increased by the plant growth regulator paclobutrazol

“…This good grain yield performance could be due to the shortest ASI with optimal fertilization and least reduction in kernel number (Table 1, Figure 4a). Cultivar Fabregas showed a 9%** decrease in grain yield, which was similar to our previous study, although in this case the difference to the control was not significant (Hütsch & Schubert, 2018).…”

“…Excessive vegetative growth can aggravate water limitations by using too much water before flowering (Passioura & Angus, 2010), as sufficient water availability during the reproductive period is particularly important for yield performance (Yang & Grassini, 2014). The smaller PAC-treated maize plants of our previous study showed a significantly reduced water consumption in comparison with the untreated control (Hütsch & Schubert, 2018). For the cultivar Fabregas, which showed no significant grain yield depression, the water-use efficiency (WUE grain ) was improved by 19% around the time of silking.…”

“…Maize plants (Zea mays L.) were cultivated according to Hütsch and Schubert (2018) using the container technique. 120 L plastic containers were filled with 145 kg of a Luvisol subsoil (loam: 25.4% clay, 40.1% silt, 34.5% sand; CAL-P: 7.2 mg P kg −1 , CAL-K: 53.6 mg K kg -1 ; pH (CaCl 2 ) 5.5 prior to liming).…”

“…Additionally, the older cultivars Fabregas and Pioneer 3906 were grown for comparing the results with our previous study (Hütsch & Schubert, 2018). These six cultivars were chosen in order to achieve a high synchronization in plant ontogenesis.…”

Plant growth regulators interact with elevated temperature to alter heat stress signaling via the Unfolded Protein Response in maize

“…Compact plants have advantages such as less energy expenditure towards shoot growth, which allows the plant to put in more energy towards flowering, reproduction, and survival 17 . Paclobutrazol has recently been shown to reduce lodging and increase stem strength in maize, along with reducing plant height 18,19 ; low levels of uniconazole application increased abscisic acid and decreased gibberellic acid in both foliar and leaf treatments in maize kernels 20 and reduced plant lodging 21 .…”