Dynamic distribution and the role of abscisic acid during seed development of a lady’s slipper orchid,Cypripedium formosanum

Background and Aims Although abscisic acid (ABA) is commonly recognized as a primary cause of seed dormancy, there is a lack of information on the role of ABA during orchid seed development. In order to address this issue, the localization and quantification of ABA were determined in developing seeds of Cypripedium formosanum.Methods The endogenous ABA profile of seeds was measured by enzyme-linked immunosorbent assay (ELISA). Temporal and spatial distributions of ABA in developing seeds were visualized by immunohistochemical staining with monoclonal ABA antibodies. Fluoridone was applied to test the causal relationship between ABA content and seed germinability.Key Results ABA content was low at the proembryo stage, then increased rapidly from 120 to 150 days after pollination (DAP), accompanied by a progressive decrease in water content and seed germination. Immunofluorescence signals indicated an increase in fluorescence over time from the proembryo stage to seed maturation. From immunogold labelling, gold particles could be seen within the cytoplasm of embryo-proper cells during the early stages of seed development. As seeds approached maturity, increased localization of gold particles was observed in the periplasmic space, the plasmalemma between embryo-proper cells, the surface wall of the embryo proper, and the inner walls of inner seed-coat cells. At maturity, gold particles were found mainly in the apoplast, such as the surface wall of the embryo proper, and the shrivelled inner and outer seed coats. Injection of fluoridone into capsules resulted in enhanced germination of mature seeds.Conclusions The results indicate that ABA is the key inhibitor of germination in C. formosanum. The distinct accumulation pattern of ABA suggests that it is synthesized in the cytosol of embryo cells during the early stages of seed development, and then exported to the apoplastic region of the cells for subsequent regulatory processes as seeds approach maturity.     

Alleviation of Negative Effects of Water Stress in Two Contrasting Wheat Genotypes by Calcium and Abscisic Acid

The individual and interactive role of calcium and abscisic acid (ABA) in amelioration of water stress simulated by polyethylene glycol (PEG) 6000 was investigated in two contrasting wheat genotypes. PEG solution (osmotic potential –1.5 MPa) was applied to 10-d-old seedlings growing under controlled conditions and changes in photosynthetic rate, activities of ribulose-1,5-bisphosphate carboxylase and phosphoenolpyruvate carboxylase, water potential and stomatal conductance were observed in the presence of 0.1 mM ABA, 5 mM calcium chloride, 1 mM verapamil (Ca²⁺ channel blocker), and 1 mM fluridone (inhibitor of ABA biosynthesis). ABA and calcium chloride ameliorated the effects of water stress and the combination of the two was more effective. The two genotypes varied for their sensitivity to ABA and Ca²⁺ under stress. As was evident from application of their inhibitors, ABA caused more alleviation in C 306 (drought tolerant) while HD 2380 (drought susceptible) was more sensitive to Ca²⁺.     

外源ABA对藜麦种子萌发及ABA相关基因表达的影响

穗发芽会导致藜麦籽粒产量和品质严重受损,而脱落酸(ABA)与种子萌发和休眠密切相关。该研究以易穗发芽的‘大黑藜3’(BBQ3)、‘白藜6’(WQ6)和抗穗发芽的‘小黑藜1’(SBQ1)和‘白藜4’(WQ4)为试验材料,在种子萌发3 d内施加不同浓度ABA和氟啶酮(FL),探究ABA和FL对两种粒色藜麦种子萌发、ABA含量以及ABA合成基因NCED、裂解基因8′OH和信号转导基因ABI3表达的影响。结果表明：(1)各藜麦种子萌发均受到各浓度外源ABA抑制,并以25μmol·L^-1浓度效果最佳,同时受到外源低浓度FL促进,且施用2.5μmol·L^-1浓度即可;外源ABA和FL处理的SBQ1和WQ4发芽率降低和升高幅度分别小于BBQ3和WQ6。(2)对照组SBQ1和WQ4种子内源ABA含量分别显著高于BBQ3和WQ6;外源ABA处理可显著提高藜麦种子内源ABA含量,且WQ4显著高于WQ6,种皮略厚的SBQ1内源ABA含量显著低于BBQ3;外源FL处理下4份材料种子内源ABA含量均有所下降,但只有SBQ1达到显著水平。(3)对照组中,SBQ1和WQ4...