Greenhouse and laboratory studies were conducted to examine certain characteristics of RPA 201772 and how they may affect its utility. 14C-RPA 201772 was used to determine the stability of RPA 201772 in various pH spray solutions over time. After 24 h, degradation of RPA 201772 was 20, 36, and 93% in spray solutions adjusted to pH 4.0, 7.0, and 10.0, respectively. The major metabolite was diketonitrile (DKN), which is herbicidally active. In addition, 9 and 15% of the RPA 201772 had degraded into an inactive benzoic acid derivative at pH 7.0 and 10.0, respectively. The differences in herbicidal activity of RPA 201772 and its metabolite DKN were also evaluated. Corn seeds and velvetleaf seeds readily imbibed RPA 201772, but only low levels of DKN were imbibed. Preemergence (applications of RPA 201772 and DKN were equally active on corn and velvetleaf. Further studies determined that the principal sites of uptake of RPA 201772 by corn was roots and seeds for four different corn hybrids. Another study determined that light was required for RPA 201772 activity. Corn shoots from seeds germinated under 14 h of light exhibited rate-dependent injury, while corn germinated and grown in the darkness was not injured.

The seeds of Schinus molle are referred to as displaying physical dormancy because of their water-impermeable endocarp. Therefore, this work aimed to evaluate the germination of S. molle seeds as related to environmental conditions, scarification, storage time and seed anatomy. Various experiments were conducted to test the alleviation of dormancy in newly collected and stored seeds. Acid-scarified seeds incubated under continuous light at 25°C showed greatest vigour and germination. The separation of seeds by specific gravity revealed a higher germination percentage for those seeds that sank. In addition, dry storage alleviated dormancy with a remarkable increase in the various germination parameters. Overall, germination traits decreased after prolonged storage, but even after 12 months the means for germination parameters for stored seeds were still higher than those of newly collected ones. S. molle seeds remain attached to parts of the fruit mesocarp and endocarp. The mesocarp contains several layers of parenchyma showing secretory cavities. The endocarp consists of three layers of sclereids surrounding the embryo. Acid scarification strongly changed the structure of the external layers in the mesocarp, digesting parenchyma cells and removing the contents from both parenchyma cells and the secretory cavities; this improved water uptake during imbibition, which occurred only at the carpellary hilar slit. In conclusion, S. molle seeds are positively photoblastic and show physiological dormancy which can be alleviated by acid scarification and dry storage. Seeds can be stored for over 12 months without significant losses in germination parameters compared to newly collected seeds.

Seeds of Sisymbrium officinale display physiological dormancy and require nitrate to germinate. Rupture of the testa precedes radicle protrusion through the endosperm (germination sensu stricto). While both endosperm rupture and testa rupture (TR) required nitrate, endosperm rupture was fully inhibited by abscisic acid (ABA) but TR was not inhibited. The gibberellic acid (GA)-synthesis inhibitor paclobutrazol prevented TR, which was reverted by exogenous GA4 but not by nitrate. The orientation of TR was transverse, which prompted the question whether seeds elongate prior to radicle protrusion, concurrent with an increase in water content. Between 9 h and 1 d no increase in length or water content was observed. During incubation in ABA the length of imbibed seeds without TR did not increase between 1 and 5 d, whereas nitrate added to ABA induced TR and a 94% increase in length. At the same time the water content of seeds without TR increased by 18%, while the water content of seeds with TR increased by 38%. Length and water content were correlated in a single-seed analysis for seeds with TR, but not for seeds without TR. Increased length was also observed in Arabidopsis seeds with nitrate-induced TR. These results indicate that prior to endosperm rupture dormancy release by nitrate is accompanied by TR, seed elongation and an increase in water content. A new multiphasic model is proposed for the imbibition curve, where the second phase of the classical triphasic curve is split into three sub-phases, of which phases IIB and IIC are associated with TR.