The effect of light quality on plant physiology, photosynthetic, and stress response in Arabidopsis thaliana leaves

The impacts of wavelengths in 500–600 nm on plant response and their underlying mechanisms remain elusive and required further investigation. Here, we investigated the effect of light quality on leaf area growth, biomass, pigments content, and net photosynthetic rate (Pn) across three Arabidopsis thaliana accessions, along with changes in transcription, photosynthates content, and antioxidative enzyme activity. Eleven-leaves plants were treated with BL; 450 nm, AL; 595 nm, RL; 650 nm, and FL; 400–700 nm as control. RL significantly increased leaf area growth, biomass, and promoted Pn. BL increased leaf area growth, carotenoid and anthocyanin content. AL significantly reduced leaf area growth and biomass, while Pn remained unaffected. Petiole elongation was further observed across accessions under AL. To explore the underlying mechanisms under AL, expression of key marker genes involved in light-responsive photosynthetic reaction, enzymatic activity of antioxidants, and content of photosynthates were monitored in Col-0 under AL, RL (as contrast), and FL (as control). AL induced transcription of GSH2 and PSBA, while downregulated NPQ1 and FNR2. Photosynthates, including proteins and starches, showed lower content under AL. SOD and APX showed enhanced enzymatic activity under AL. These results provide insight into physiological and photosynthetic responses to light quality, in addition to identifying putative protective-mechanisms that may be induced to cope with lighting-stress in order to enhance plant stress tolerance.

Automatic system for follow-up of leaf area growth individualized by plants

With the advancement of technology and the low cost of equipment, the possibility to analyze and accompany vegetative vigor in real time is the reality. The vigor is related with the leaf area index, which is a metric obtained by a relation between the leaf area and the soil area occupied by the plant. This research had as objective create an automated system of low cost for acquisition and analysis of images, building an accompaniment of the leaf area index of individualized plants.

Fitness costs of susceptible and resistant radish biotypes to ALS-inhibitor herbicides

Radish is an important weed that causes yield reduction in winter crops in southern Brazil. The control chemical of radish is an important and essential step to prevent damage on crops. However the intensive use of ALS-inhibitors herbicides favors the selection resistant biotypes. The selection can influence the adaptive traits of biotypes with physiological changes and growth variables and plant reproduction. The objective of the study was compare the fitness costs of susceptible and resistant radish biotypes to ALS-inhibitors herbicides. The experiment was conducted in greenhouse using completely randomized design with five replications. The treatments were arranged in factorial arrangement corresponding to susceptible and resistant biotypes (B1 and B4) and nine sampling times (14, 28, 42, 56, 70, 84, 98, 112 and 126 days after emergency), respectively. The variables evaluated were plant height, shoot dry matter, root dry matter, total dry matter, leaf area, growth rate, relative growth rate, leaf area ratio, number of siliques and seeds produced per plant. The results showed that the resistant biotype (B4) had no fitness costs when compared to the susceptible biotype (B1).

Application of the Richards function to the description of leaf area growth in maize (Zea mays L.)

The leaf area growth in maize was approximated basing on the Richards function in the form of: y=A[l+b exp(-kt)]^1/(1-m) . The constant coefficients of the Richards function were found by means of the Marquardt's method. The initial values of parameters were given basing on results of the preliminary approximation of the growth process by means of logistic function y = A[l+b exp(-kt)]^-1. The procedure of nonlinear regression was found to be useful (curvilinear determination coefficient R² = 0.995). The Richards curve precisely describes the course of changes of the leaf area in maize since sprouting to a tassel flowering phase.

A mathematical description of maize leaf area growth using a logistic curve

In this paper, an attempt is made to apply the Verhulst-Pearl and the Robertson logistic curves to the description of maize plant growth. The changes with time of the total leaf area were taken as the parameter expressing the growth kinetics. The constant coefficients in the Verhulst-Pearl and Robertson equations were calculated with the help of a logarithmic transformation and the least square method. On this basis, the growth kinetics of the studied maize lines and hybrid were compared. The applicability of logistic curves to the description of completed growth processes was demonstrated as was the fact that Robertson's equation is better suited for mathematical calculations.

Interactions between plant hormones and light quality signaling in regulating the shoot growth of Arabidopsis thaliana seedlings

The effects of a decrease in red to far-red (R/FR) ratio on shoot growth of two-week-old Arabidopsis thaliana (L.) Heynh. seedlings were examined in the context of possible causal involvement of key plant growth hormones. Decreasing the R/FR ratio significantly increased petiole elongation and leaf area expansion of the Columbia (Col) line seedlings. In contrast, seedlings of the Landsberg erecta (Ler) line showed no significant change in leaf area and only a marginal increase in petiole growth. This low R/FR ratio-induced growth was accompanied by significant increases in concentrations of the growth “effector” gibberellin (GA4) and an auxin (indole-3-acetic acid (IAA)) in shoot tissues of Col. However, cytokinins (CKs) in Col shoot tissues were decreased and ethylene evolution was reduced when the R/FR ratio was decreased from that of normal sunlight to a low R/FR ratio. Several A. thaliana genotypes with plant hormone-related mutations were also assessed, including auxin resistant, axr2-1; GA insensitive, gai-1; and ethylene over-producing, eto2. None of these increased their petiole length or leaf area growth in response to lowering the R/FR ratio. We thus conclude that both GA4 and IAA are causally involved in the increased shoot growth of A. thaliana Col seedlings that occurs in response to a lower than normal R/FR ratio.