Defoliation of sweet corn plants under irrigation depths and its impact on gas exchange

Abstract

A B S T R A C TThe objective of this work was to evaluate leaf gas exchanges of sweet corn as a function of defoliation when submitted to different irrigation depths. The experimental design was randomized blocks in split-plot scheme, with four irrigation depths in the plots [50, 75, 100 and 125% of crop evapotranspiration (ETc)], and three levels of defoliation in the subplots (0%, control; 35%, removal of four fully expanded leaves; 100%, total removal of the leaves -section of the aerial part) with three replicates. Defoliation was manually performed when the plant had four fully expanded leaves. It was verified that the dephs of irrigation and defoliation levels affect leaf gas exchanges in sweet corn plants, allowing the conclusion that the plant tends to activate a mechanism of photosynthetic compensation, when subjected to leaf stress, which can vary according to the degree of severity and water availability to which it is submitted. The most expressive values of gas exchanges in sweet corn plants that did not have defoliation were generally observed at irrigation depths estimated between 87 and 99% ETc and, in the treatments with defoliation, regardless of the level, at irrigation depth of 125% ETc. Desfolha em plantas de milho doce sob diferentes lâminas de irrigação e seu impacto nas trocas gasosas R E S U M O Objetivou-se neste trabalho avaliar as trocas gasosas foliares de plantas de milho doce em função da desfolha, quando submetidas a diferentes lâminas de irrigação. O delineamento experimental foi em blocos casualizados em esquema de parcelas subdivididas, tendo nas parcelas quatro lâminas de irrigação 50, 75, 100 e 125% da evapotranspiração da cultura (ETc) e nas subparcelas três níveis de desfolha (0%, testemunha; 35%, remoção de quatro folhas completamente expandidas; 100% remoção total das folhas -secção da parte aérea) com três repetições, sendo a desfolha realizada manualmente quando a planta apresentava quatro folhas completamente expandidas. Verificou-se que os níveis de irrigação e desfolha afetam as trocas gasosas foliares em plantas de milho doce, permitindo a conclusão de que a planta quando submetida a estresses foliares, tende a ativar um mecanismo de compensação fotossintética, podendo variar em função do grau de severidade e da disponibilidade hídrica a qual está submetida. Os valores mais expressivos de trocas gasosas em folhas de milho doce que não tiveram desfolha foram, de forma geral, observados nas lâminas de irrigação estimadas entre 87 e 99% da ETc e nos tratamentos com desfolha, independente do nível ocorrido, na lâmina de 125% da ETc.

Can inoculation with diazotrophic bacteria decrease the productivity loss of defoliated Vigna unguiculata (L.) Walp?

“…Such facts interfere with the availability of chemical energy (ATP) from photosynthesis, which is produced only in cells containing chlorophyll in the presence of light (Ibrahim et al, 2010;Addai & Ghanney, 2018;Lima-Primo et al, 2019). Reduction of leaf area interferes with photosynthesis and, consequently, with hormonal equilibrium, index of chlorophylls, stomatic resistance, and ATP production (Ibrahim et al, 2010;Santos et al, 2017;Addai & Ghanney, 2018), resulting in a production decline (Figures 3 and 4).…”

“…During its cycle, cowpea is challenged by defoliating herbivorous insects. Such insects reduce the leaf area and photosynthetic capacity of the plant, promoting significant production losses (Ibrahim et al, 2010;Santos et al, 2017;Smiderle et al, 2017;Addai & Ghanney, 2018;Lima-Primo et al, 2019).…”