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Phytohormones are important for the growth and development of plants. The objective of the experiment was to investigate the effect of foliar application of uniconazole (UCZ) at the four-leaf stage on hormone crosstalk and production of winter wheat. An experiment was carried out during 2015-2016 and 2016-2017 growth season in a semi-arid region, where UCZ at a concentration of 0 (CK, distilled water), 15 (FU 15 ), 30 (FU 30 ), and 45 (FU 45 ) mg L -1 were sprayed on wheat crop at the four-leaf stage at a rate of 138.8 mL m -2 . UCZ alters the endogenous hormone contents in flag leaves and in grains. UCZ inhibited gibberellic acid (GA) in flag leaves and in grains where the lower GA with UCZ improved the zeatin + zeatin riboside (Z + ZR) and abscisic acid (ABA) contents. The lower GA and higher Z + ZR and ABA contents with UCZ-treated plants improved the chlorophyll content and canopy apparent photosynthesis (CAP) as well as the grain-filling characteristics. The Z + ZR and ABA in flag leaves were positively correlated with chlorophyll content and CAP value while negatively with GA. Moreover, the Z + ZR and ABA were positively correlated with maximum grain weight, mean grain-filling rate, and maximum grain-filling rate, while negatively with GA level. Treatment FU 30 significantly improved the chlorophyll content, CAP value, spike weight, grain-filling characteristics, and hormone contents of Z + ZR and ABA while it decreased the GA level. The hormone crosstalk with UCZ significantly increased the yield of wheat crop, where FU 30 treatment performs better.

In northern China, large-spike wheat (Triticum aestivum L) is considered to have significant potential for increasing yields due to its greater single-plant productivity despite its lower percentage of effective tillers, and increasing the plant density is an effective means of achieving a higher grain yield. However, with increases in plant density, the amount of solar radiation intercepted by lower strata leaves is decreased and the rate of leaf senescence is accelerated. Row spacing can be manipulated to optimize the plant spatial distribution under high plant density, therefore improving light conditions within the canopy. Consequently, field experiments were conducted from 2010 to 2012 to investigate whether changes in row spacing under high plant density led to differences in canopy apparent photosynthesis (CAP), individual leaf photosynthesis and grain yield. Two different spike-type winter wheat cultivars, Jimai22 (a small-spike cultivar as a control cultivar) and Wennong6 (a large-spike cultivar), were grown at a constant plant density of 3,600,000 plants ha(-1) (a relatively higher plant density) over a wide range of row spacing as follows: 5-cm row spacing (R0), 15-cm row spacing (R1), 25-cm conventional row spacing (R2), and 35-cm row spacing (R3). The two-year investigations revealed that increased row spacing exhibited a significantly higher light transmission ratio (LT), which improved light conditions within the canopy; however, excessive light leakage losses in R2 and R3 treatments were not favorable to improved irradiation energy utilization efficiency. Aboveground biomass accumulation was influenced by row spacing. Two spike-type wheat accumulated greater biomass under 15-cm row spacing compared to other row spacing treatments, although a markedly improved photosynthetic rate (PN), effective quantum yield of photosystem II (ΦPSII) and maximal efficiency of photosystem II photochemistry (Fv/Fm) in the penultimate and third leaves were observed in R2 and R3 treatments. At the same time, a longer duration of CAP and green leaf area was maintained in R1 during grain filling. Compared with conventional row spacing, Wennong6 in R1 treatment obtained 21.0% and 19.1% higher grain yield in 2011 and 2012, respectively, while for Jimai22 it increased by 11.3% and 11.4%, respectively. A close association of yield with CAP and LAI at mid-grain filling was observed. In conclusion, for the tested growing conditions, decreasing the row spacing to an optimal distance (15 cm) maintained a longer duration of LAI and CAP during grain filling, made a better coordination of group and individual leaf photosynthesis, and accumulated higher aboveground biomass, leading to a greater grain yield. In addition, Wennong6 had a more rational canopy architecture than Jimai22 (improved LT and higher LAI) and CAP under 15-cm row spacing, leading to a higher grain yield, which indicated that the large-spike type cultivar has the potential to obtain higher yields by increasing plant density through optimum row spacing allocation (15 cm).

Excising the upper leaves strata of maize crops cultivated at high stand densities could possibly optimize canopy architecture to achieve enhanced canopy apparent photosynthesis, a more favorable distribution of 13 C-photosynthates to grain, and ultimately higher grain yields. To test this hypothesis, we conducted a leaf removal experiment in 2012 and 2013 growing seasons in Shandong, a province in the North China Plain. Jinhai5, a corn cultivar planted widely across China, was grown at a density of 105,000 plants ha −1 until 3 days after silking (DAS), when plants were subjected to the removal of the uppermost and next leaves (S 2 ), the four uppermost leaves (S 4 ) or the six uppermost leaves (S 6 ), with no leaf removal as control (S 0 ). In the S 2 treatment we found a longer duration of canopy apparent photosynthesis (CAP) and green leaf area index (LAI), higher total dry matter weight at physiological maturity as well as greater harvest index (HI) compared to the control, whereas those in the excessive leaf removal treatments (S 4 and S 6 ) declined substantially. In addition, modification of the number of leaves above the ear leaf led to different patterns of allocation of 13 C-photosynthates. Excising two leaves promoted the distribution of 13 C-photosynthates to grains, while that allocation decreased in the S 4 and S 6 treatments, which can be interpreted as a result of increased retention of 13 C-photosynthates in the stem and ear bracts. Plants in S 2 treatment displayed a yield advantage under high plant density due to higher kernel weight and more harvested ears. Relative to control, plants in the S 2 treatment had 15% and 12% higher grain yields in 2012 and 2013, respectively. However, the removal of four or six leaves at the very early grain filling period, when kernel sink capacity is being established, caused a marked reduction in yields due to decreased both kernel number per plant and kernel weight, despite a relatively higher biomass availability per kernel. In conclusion, excising two leaves (the uppermost and next leaves) of maize crops cultivated at high plant density delayed leaf senescence, enhanced canopy photosynthesis and dry matter accumulation, leading to a higher post-silking source–sink ratio with its positive impact on kernel weight and higher grain yield. [ABSTRACT FROM AUTHOR]

Highlights • The effects of uniconazole applied alone or in combination with manganese on the anti-oxidant defense system of winter wheat were studied. • Uniconazole applied alone or in combination with manganese improved the photosynthetic efficiency of wheat. • Uniconazole applied alone or in combination with manganese enhanced the anti-oxidant defense system. • The anti-oxidant enzymes activities were negatively correlated with reactive oxygen species. • Treatment SMU2 has significant positive effects on winter wheat production. Abstract In arid and semiarid regions, wheat productivity depends on natural precipitation, however deficit and unpredictable precipitation leads to reduced production. Uniconazole application can significantly reduce the accumulation of reactive oxygen species (ROS) by enhancing the anti-oxidant enzymes activities and improve the wheat production in semiarid regions. The objective of the current study was to test the hypothesis, whether uniconazole applied alone or in combination with manganese could improve the wheat productivity by enhancing the photosynthetic efficiency and antioxidant defense system. Uniconazole was applied as seed soaking at the concentrations of 0 (CK), 15 (SU1), 30 (SU2), and 45 (SU3) mg L–1, and in the second experiment with manganese at the concentrations of 0.06 g L–1 (Mn), 0.06 g L–1 manganese + 15 mg L–1 uniconazole (SMU1), 0.06 g L–1 manganese + 30 mg L–1 uniconazole (SMU2), and 0.06 g L–1 manganese + 45 mg L–1 uniconazole (SMU3), respectively. Uniconazole applied alone or in combination with manganese significantly reduced the ROS accumulation by enhancing the anti-oxidant enzymes activities. Treatments SMU2 and SU2 improved significantly the photosynthetic efficiency, soluble protein content, and leaf area plant–1 and thus increased the grain yield. Treatments SMU2 and SU2 significantly enhanced the anti-oxidant enzymes activities of superoxide dismutase (SOD), peroxidase (POD), catalase (CAT), and ascorbate peroxidase (APX), while reduced the accumulations of MDA, proline, and ROS. The chlorophyll a and b contents, net photosynthetic rate, soluble protein content, and anti-oxidant enzymes activities were significantly negatively correlated with ROS, MDA, and proline contents. Uniconazole application in combination with manganese treatments significantly improved the wheat production. Uniconazole application in combination with manganese at the concentration of 30 mg L–1 and 0.06 g L–1 or uniconazole applied alone at a concentration of 30 mg L–1 significantly enhanced the anti-oxidant defense system and winter wheat production in semiarid regions. [ABSTRACT FROM AUTHOR]