Background:The growing use of nitrogen topdressing fertilisation, combined with late sowing of maize crops, causes greater sensitivity to lodging and breaking of plant stems, and poses risks to yield and grain quality. Thus, plant growth retardants are currently an option to mitigate losses resulting from adverse effects. Aims: The objective of this work was to evaluate the influence of using the plant growth retardant prohexadione-calcium (Pro.Ca) in response to application of different nitrogen levels on morphometric and productive characteristics of maize after late sowing. Study Design: The experiment used a randomized block design (RBD) with four replications.

The use of prohexadione-calcium (ProCa) is a management alternative to mitigate greater predisposition to vegetative growth. The objective of this study was to evaluate the use of ProCa in combination with two doses of nitrogen fertilizer in cover, in the morphophysiological and productive performance of corn hybrids. Experiments were performed with corn hybrids AS1757 VTPRO3 and AG9025 VTPRO3 , in a randomized block design, factorial 2×2, with four replications. The treatments consisted of the application of nitrogen fertilizer in cover, 1x and 2x the recommended dose, and in the absence or presence of the application of ProCa. The single effect of ProCa on the hybrid AS1757 VTPRO3 increased the SPAD index by 20%; in the AG9025 VTPRO3 hybrid there was a reduction of 8.6 cm in the height of ear insertion and increments of 2.2 mm in the stem diameter. The application of ProCa with 2x N ha -1 increased, on average, 8.2% the number of leaves of the AS1757 VTPRO3 hybrid compared to the application to 1x N ha -1 . There is single effect of ProCa on morphophysiological characteristics in the tested hybrids, but without affecting its grain yield. The use of ProCa in association with 2x N ha -1 does not mitigate the vegetative growth in the genotypes, sown late in the South of Brazil.

Water deficiency reduces leaf expansion and photosynthetic efficiency, potentially reducing the ability to withstand leaf area (LA) loss. This study aimed to evaluate the effects of water restriction on soybean tolerance to defoliation in the vegetative and reproductive periods of development. Two experiments were conducted in a greenhouse located in Lages, Santa Catarina State Brazil, during the 2017/2018 growing season. Cultivar NA 5909 RG was subjected to three WR levels (none, moderate, and severe) and five defoliation levels (0, 17, 33, 50, and 67%). Defoliation occurred at the V6 stage in the first experiment and R3 in the second. WR occurred for 7 days after defoliation. LA at R2 and R5 after defoliation at V6 and R3 decreased by 27.5 and 64.6%, respectively, regardless of WR. LA between V6 and R2 was not influenced by WR or defoliation. Moderate or severe WR reduced plant ability to recover LA between R3 and R5. Severe WR decreased grain production by 22.2% in the vegetative period and 21.2% per plant in the reproductive period compared to that of the control, regardless of defoliation. The highest defoliation level reduced grain production per plant by 24.7 and 24.3% relative to the control at stages V6 and R3, respectively, regardless of WR. WR imposed at the vegetative and reproductive stages did not increase defoliation sensitivity.

Trinexapac-ethyl (henceforth referred to as trinexapac) is a growth regulator that can mitigate some undesirable vegetative growth in Poaceae plants, reducing lodging and optimizing the distribution of photoassimilates to reproductive organs. The objective of this research was to evaluate the morphophysiological and productive responses of rye cultivars and trinexapac doses applied at different phenological stages of plants. Two field experiments were performed in two different seasons. In the 2015 growing season, 8 doses of trinexapac were evaluated: 0, 75, 85, 100, 115, 130, 150, 200 g ha-1 of active ingredient (a.i.), applied at the plant growth stage with the 4th node visible on the main stem (GS34). In the 2018 growing season, two cultivars (IPR 89 and BRS Serrano) and five doses of trinexapac were evaluated: 0, 50, 100, 150 and 200 g a.i. ha-1, applied at the plant growth stage with the 6th node visible on the main stem (GS36). The morphophysiological, productive and qualitative characteristics of grains were evaluated. In the 2015 season, trinexapac applied to shoot plants at GS34 only have low response in decreased plant lodging from around 20% to 10%. However, in the 2018 season, the application of trinexapac on plants at GS36, resulted in lower plant height, associated with reduced lodging and better quality of rye grains. Cultivar IPR 89 showed higher values for yield components and grain quality in comparison to cultivar BRS Serrano. Reduced lodging is dependent on speed of resumption of plant height growth, and the magnitude of response to trinexapac is also stage-cultivar-dose-dependent; in rye, the best response to trinexapac was found at GS 36 in comparison to GS 34, and for IPR 89 in comparison to BRS Serrano cultivar, respectively, with a dose range from 100 to 150 g ai ha-1. In conclusion, trinexapac (around 150 g a.i. ha-1), when applied to plants at GS36, reduces plant height, reduces the lodging index and enables the harvest of high-quality grains.