Heracleum sosnowskyi seed development under the effect of exogenous application of GA₃

Abstract

Numerous studies have demonstrated the impact of exogenous gibberellin on fleshy fruit formation, but the effect on dry fruits is not yet well known. To test the role of gibberellin (GA3) in dry fruit formation, we analysed the impact of exogenous GA3 on the invasive plant Sosnowsky’s hogweed (H. sosnowskyi Manden.) seed development and germination. Treatment of GA3 concentrations of 0.07 mM, 0.14 mM, 0.28 mM, 0.43 mM was applied to flowers at the early stage of development. Seeds were collected from treated satellite umbels. It was observed that GA3treatment did not have a significant effect on the size of H. sosnowskyi seeds, but caused various changes in their shape. The data on semi-thin longitudinal sections of H. sosnowskyi mericarps and SEM micrographs of embryos showed that the embryos in GA3 (0.43 mM) treated variants were at torpedo stage, while in control variants—mature embryos. The germination of seeds of each variant was estimated by burying them in the soil. Our studies indicated that GA3 application reduced the germination of H. sosnowskyi seed from 98.0% (control) to 16.5% (GA3 concentration 0.43 mM). It was assumed that exogenous application of GA3 had influence on the development of dry Sosnowsky’s hogweed seeds and could be used to inhibit the spread of this invasive plant.

Molecular mechanisms and hormonal regulation underpinning morphological dormancy: a case study using Apium graveolens (Apiaceae)

“…Exogenous application of auxin during carrot reproduction enhanced the yield, size and quality of fruits, with increased germination percentages and vigour (Noor et al, 2020). Similarly, gibberellin or TIBA application reduced the germination percentages of Heracleum sosnowskyi (Koryzniene et al, 2019). Our work on celery and these examples from other Apiaceae MD/MPD fruits support the view that, as in PD/ ND species, GA, ABA and IAA interact to control seed development, accumulate transiently during seed development and are degraded during late seed development (Figure 7).…”

“…In A. thaliana seeds, auxin controls seed dormancy through stimulation of ABA signalling (Liu et al, 2013) and is known as a key regulator of dormancy, longevity and maturation in PD seeds (Matilla, 2020;Pellizzaro et al, 2020;Shu et al, 2016). Auxin transport appears to be important for Apiaceae seed development (Koryzniene et al, 2019) and germination (Figure 6). Although IAA treatment did not appreciably affect celery germination under optimal conditions (Figure 6), it promoted dill fruit germination upon salt stress (Unver and Tilki, 2012) and enhanced the size, germination percentages and vigour of carrot fruits (Noor et al, 2020).…”

Gibberellic Acid (GA3) Applied to Flowering Heracleum sosnowskyi Decreases Seed Viability Even If Seed Development Is Not Inhibited

“…Such an approach could be useful with the invasive monocarpic weed species H. sosnowskyi , but a protocol remains to be developed and its efficiency demonstrated. Results from our earlier studies with this species suggest that the disturbance of mericarp development induced by exogenous GA 3 -application can contribute to decreased germination [ 21 ]. Meanwhile, in the current study, the double application of GA 3 shows a dose response and consistent efficacy in reducing seed viability in different years.…”

“…Artificial parthenocarpy in fleshy fruits is often induced by the application of exogenous auxins and gibberellins on flowers before anthesis to obtain seedless fruits for commercial purposes [ 19 ]. In some cases, to increase parthenocarpic fruit sets and their growth, apical bud and axillary shoots are removed [ 20 , 21 ]. The ability of exogenous gibberellic acid (GA 3 ) to induce parthenocarpy is often accompanied by changes in fruit morphology and histology [ 22 , 23 , 24 ].…”

“…It has been shown that in Sosnowsky’s hogweed, a single application of exogenous GA 3 to satellite umbels together with mechanical manipulations (terminal umbel decapitation, axillary buds removement and prevention of cross-pollination) which enhanced the GA 3 effect, can cause deformations in fruits, slow down embryo development and decrease seed viability assessed as germination [ 21 ]. However, as a more detailed study of the disturbances in seed development induced by exogenous GA 3 application on intact plants is still lacking, alternative mechanisms for the GA 3 -induced impairment of germination cannot be ruled out.…”