Variations in endogenous polyamine content of maize calli obtained from zygotic and androgenetic embryos

A comparative study of polyamine (putrescine, spermidine and spermine) levels was conducted with maize calli originating from a) immature embryos and b) pollen embryos capable of plant regeneration. The differences observed in the studied parameters of the two kinds of calluses are related to their cellular origin and to their regeneration capacity. Moreover, only the calluses proceeding from immature embryos differentiated into preembryogenic structures, which eventually developed into plants. Although total polyamine levels in pollenderived calluses were significantly higher than those from immature embryos, spermidine and spermine were the predominant polyamines in both culture types. Furthermore, polyamine fractions of these calluses also showed differences. All these phenomena may be related with the differences observed in the callus embryogenic response. These findings may be useful in understanding the implication of polyaminesin embryogenetic processes.Abbreviations IEC immature-embryo calluses - PAs polyamines - PEC pollen-embryo calluses - PH insoluble conjugated PA fraction - Put putrescine - S free PA fraction - SH soluble conjugated PA fraction - Spd spermidine - Spm spermine 2,4d-2,4 dichlorophenoxyacetic acid     

Salt Stress Induces Increase in Starch Accumulation in Duckweed (Lemna aequinoctialis,Lemnaceae): Biochemical and Physiological Aspects

In this study, antioxidant processes were searched for in macrophyte duckweed to investigate tolerance mechanisms in this species against oxidative damage caused by salinity stress. Biochemical and histological analyses were performed on four Lemna aequinoctialis clones grown in Schenk-Hildebrandt medium, 0.5 × SH, supplemented with 1% sucrose liquid medium containing or not containing NaCl in different NaCl concentrations (0, 25 and 50 mM). For most clones, the salt stress effects caused growth inhibition and antioxidant responses at 50 mM NaCl. Also, starch and reducing sugar accumulations were increased with salt, whereas the photosynthetic pigment content was reduced in clone L. aequinoctialis 5569. The plant growth inhibition reflects the oxidative stress shown by the significant increase in malondialdehyde (MDA) and hydrogen peroxide (H₂O₂) content. In the L. aequinoctialis 5568 clone, with the highest MDA levels, no antioxidant enzymatic activity was observed. The L. aequinoctialis 5570 clone presented higher ascorbate peroxidase and catalase activities in parallel, indicating that the efficiency of the defence mechanism relies on synchrony between such enzyme activities toward successive elimination of reactive oxygen species and resulting in the assurance of some level of protection of the metabolism from oxidative damage. Considering the moderate salt stress (25 mM), the maintenance of MDA content and small growth inhibition associated with the high starch production suggested the acclimation efficiency of L. aequinoctialis 5570 and 5567 clones, indicating that they may be suitable for cultivation under moderate saline conditions, serving as biofuel feedstock. In addition, this study demonstrates great intraspecific phenotypic plasticity of duckweed, L. aequinoctialis, from closely related clones.

     

Using LED lighting in somatic embryogenesis and micropropagation of an elite sugarcane variety and its effect on redox metabolism during acclimatization

This study investigated the ability of a light emitting diode (LED) to induce somatic embryogenesis (SE), shoot multiplication, and rooting of sugarcane (RB98710). We also accessed the effects on acclimatization. MS medium was used for all stages and was supplemented with different concentrations of growth regulators according to the culture stage. The material was maintained in a growth room under fluorescent (FL) or LED (82?% red, 18?% blue) lighting after rooting plants were acclimatized. We conducted both biometric and biochemical analyses before and after acclimatization. The LED conditions favored the formation of callus; however, the FL was more efficient at plant regeneration. A histological analysis showed the formation of somatic embryos occurred through direct and indirect pathways. The plants obtained through SE and grown under LED had a higher multiplication rate over six subcultures. Shoots rooted in both light sources, but the number of shoots and the weight gain of the roots were higher under LED. The malondialdehyde (MDA) level did not differ among treatments. Our results indicate the SE induction phase should be conducted under FL and the remaining micropropagation process should be performed using LED. After acclimatization the plants grown under LED did not change the SOD and CAT activities during the first 5 days, which suggests there was no acclimatization impact. The H₂O₂ and MDA values observed do not suggest damage to membranes. There was better development, lower water loss, and higher survival rate in plants from in vitro culture under LED conditions when compared to FL.     

Water Stress-Induced Responses in the Growth,Cuticular Wax Composition,Chloroplast Pigments and Soluble Protein Content,and Redox Metabolism of Two Genotypes of Ricinus communis L.

Journal of Plant Growth Regulation - The aim of this study was to investigate the physiological and biochemical responses to three different water regimes in two castor bean genotypes (BRS Energia...