Guard cell (GC) length proved to be efficient in sorting diploids from haploids in doubled haploid development in maize (Zea mays L). It compensates for the weakness of widely used R1-nj marker approach that showed low reliability in haploids identification from tropical genotypes. Guard cell length differs between haploid and diploid plants, and these differences were evaluated in the progeny of three different induction crosses obtained using Krasnodar haploid inducer. Epidermal impressions of the abaxial surface of leaves removed from the second, third, and fourth nodes (from base to apex) were collected and measured using an optical microscope. This was also conducted on the flowering phenotype. Guard cell length varied according to germplasm source, leaf stage, and ploidy level. Mean GC length ranged from 23.67 to 33.82 μm in haploids, and from 36.1 to 41.25 μm in diploids. Based on these differences in GC length at any of the chosen leaf stages (second, third, or fourth), diploid and haploid maize plants were successfully classified. Classification efficiency was found to be more closely related to germplasm source than leaf stage. Comparing GC length according to phenotype (haploid or diploid), GC limits for classification as a diploid plant (threshold points) were estimated and ranged from 29.74 to 34.49 μm, depending on germplasm source. The highest false discovery rate was 2.93% and false negative rate was 15.06%, indicating that classification based on GC length was reliable.

L-3,4-Dihydroxyphenylalanine (L-DOPA) is an allelochemical released by roots of velvet bean (Mucuna pruriens) that affects the growth of several plant species. However, its mechanism of action is inconclusive. In this work, we compared the effects of L-DOPA (0.01-1.0 mmol L -1 ) and of aqueous extracts (300, 1200, and 3000 mg L -1 ) of velvet bean on growth and photosynthesis (gas exchange and chlorophyll a fluorescence) of soybean (Glycine max). Overall, the results showed that both L-DOPA and aqueous extracts of velvet bean reduced the growth, leaf area, photosynthetic rate (A), stomatal conductance (g s ), transpiration (E), and quantum yield of electron flow through photosystem II (PSII) in vivo (U F ). In addition, L-DOPA and aqueous extracts increased the internal CO 2 concentration (Ci) and the leaf wax and trichome density on the leaf surface, while the maximum quantum yield of PSII (F v /F m ) was not changed. These results suggest that the reduction of A should not be related exclusively to the stomatal closure, but also to limitations of the carbon metabolism, as indicated by the increase of Ci and decrease of U F . Briefly, we concluded that soybean growth inhibition by L-DOPA and aqueous extracts of velvet bean is due to the combination of damage in the root meristem and reduction in A.

Comparação de três testadores na avaliação de famílias de milho pipoca derivadas de IAC-125

ABSTRACT. The aim of this study was to evaluate the effect of high dilutions of Pulsatilla nigricans in dinamisations 6, 12, 18, 24 and 30 CH on the vigour of soybean seeds subjected to accelerated aging. The experiment was conducted according to a randomised design with 6 treatments and 10 replicates. The treatments consisted of dinamisations 6, 12, 18, 24 and 30 CH and a distilled-water control. After the treatments, the seeds were subjected to accelerated aging (48h at 42ºC) in a growth chamber (25 ± 2ºC). The study evaluated the germination, the length of primary roots and shoots, the fresh weight of roots and shoots and the enzymatic activity of peroxidase (POX-EC1.11.1.7). The variables were analysed by ANOVA, and the means were compared using the Scott-Knott test (p = 0.05). The germination and the fresh weight of roots and shoots of the seedlings treated with Pulsatilla nigricans were higher than the water control, except that CH 30 did not significantly increase the fresh weight of shoots. The dinamisations 6, 24 and 30 CH produced a lower primary root length compared with the control. The dinamisations 12, 18 and 30 CH yielded a greater length of shoots. The total length of seedlings was reduced by the high dilutions 6 and 24 CH.

Velvet bean (Mucuna pruriens) is an efficient cover forage that controls weeds, pathogens and nematodes, and the non-protein amino acid L-3,4-dihydroxyphenylalanine (L-DOPA) is its main allelochemical. The effects of 3 g L of an aqueous extract of velvet bean seeds, along with 0.5 mM L-DOPA for comparison, were evaluated in roots, stems and leaves of soybean (Glycine max). The activities of phenylalanine ammonia lyase (PAL) and cinnamyl alcohol dehydrogenase (CAD) were determined, along with the lignin content and its monomeric composition. The results revealed similar effects caused by L-DOPA and the aqueous extract. Both treatments reduced PAL and CAD activities, lignin, and lignin monomer contents in roots; PAL and CAD activities in stems, and CAD activity in leaves. These findings provide further evidence that the effects of velvet bean cover forage on root lignification were due to the L-DOPA, its major allelochemical.