Oak leaf galls: Neuroterus numismalis and Cynips quercusfolii, their structure and ultrastructure

Anatomy and surface ultrastructure of the galls induced on oak leaves by the insects – Neuroterus numismalis (Ol.) and Cynips (Diplolepis) quercusfolii L. – were investigated using a scanning electron microscope (SEM) and a light microscope (LM). The observations in SEM and in LM enabled a detailed description of these galls and comparison of their structure with that of the typical oak leaf. In N. numismalis gall, the external distal tissues were classified as similar to phellem (cork), phellogen, and phelloderm, and a lateral marginal tissue as parenchyma with the likely role of a storage tissue. In the young C. quercusfolii gall, the cells of internal, nutritive tissue, on which the larva is grazing, formed globules rising above the surface of larval chamber. Many of them seemed to be destroyed by the larval action. In the gall which attained half of its final size, the tissues near the larval chamber were already partly lignified. The microorganisms (mainly fungi) which live in the oak phyllosphere, occurred also on the galls. We believe that the deep changes in the morphogenetic program of a leaf, which are caused by the gall-forming insects, are impossible without the transfer and the integration of the insect genetic material with that of the host plant. We also postulate that a larva secrets as yet hypothetical substances, which redirect the nutrients transport from the leaf blade towards the gall and support its vital functions

Breaking seed dormancy of Astragalus penduliflorus Lam.

Astragalus penduliflorus Lam. is an alpine-subalpine species. Several isolated populations occur in Europe: in the Alps, Pyrenees, Carpathians and in central Sweden. Astragalus penduliflorus is considered as critically endangered species in Poland, growing only at the locality in the Smytnia Valley, in the Western Tatra Mountains. The population is at risk, due to the limited reproduction caused by law rate of seed germination, periodically shortened vegetation period that prevent seed development and gnawing the aerial plant parts by deer. The aim of the study was to explain the reason for the poor germination of A. penduliflorus seeds. As a result of mechanical scarification, 100% of A. penduliflorus seeds germinated, which proved that these seeds are characterized by a water-impermeable seed coat, which classified them as hard seeds that go through physical dormancy. Results obtained in this work can be used for effective reproduction and active conservation of threatened A. penduliflorus

Failure of androgenesis in Miscanthus × giganteus in vitro culture of cytologically unbalanced microspores

Miscanthus × giganteus is a popular energy crop, which due to its hybrid origin is only vegetatively reproduced. Asexual embryogenesis in anther and microspore culture leading to double haploids production could allow to regain the ability for sexual reproduction and to increase the biodiversity of the species. Therefore, the goal of this paper was to investigate the requirements of androgenesis in Miscanthus. The standard protocols used for monocotyledonous plants were applied with many modifications regarding the developmental stage of the explants at the time of culture initiation, stress treatment applied to panicles and isolated anthers as well as various chemical and physical parameters of in vitro culture conditions. Our results indicated that the induction of androgenesis in M. × giganteus is possible. However, the very low efficiency of the process and the lack of regeneration ability of the androgenic structures presently prevent the use of this technique

Oak leaf galls: Neuroterus numismalis and Cynips quercusfolii, their structure and ultrastructure

Anatomy and surface ultrastructure of the galls induced on oak leaves by the insects – Neuroterus numismalis (Ol.) and Cynips (Diplolepis) quercusfolii L. – were investigated using a scanning electron microscope (SEM) and a light microscope (LM). The observations in SEM and in LM enabled a detailed description of these galls and comparison of their structure with that of the typical oak leaf. In N. numismalis gall, the external distal tissues were classified as similar to phellem (cork), phellogen, and phelloderm, and a lateral marginal tissue as parenchyma with the likely role of a storage tissue. In the young C. quercusfolii gall, the cells of internal, nutritive tissue, on which the larva is grazing, formed globules rising above the surface of larval chamber. Many of them seemed to be destroyed by the larval action. In the gall which attained half of its final size, the tissues near the larval chamber were already partly lignified. The microorganisms (mainly fungi) which live in the oak phyllosphere, occurred also on the galls. We believe that the deep changes in the morphogenetic program of a leaf, which are caused by the gall-forming insects, are impossible without the transfer and the integration of the insect genetic material with that of the host plant. We also postulate that a larva secrets as yet hypothetical substances, which redirect the nutrients transport from the leaf blade towards the gall and support its vital functions

Sterility of Miscanthus × giganteus results from hybrid incompatibility

Miscanthus ×giganteus Greef et Deu. (Poaceae), a hybrid of Miscanthus sinensis and M. sacchariflorus native to Japan, is an ornamental and a highly lignocellulosic bioenergy crop, cultivated in the European Union as an alternative source of energy. This grass reproduces exclusively vegetatively, by rhizomes or via expensive in vitro micropropagation. The present study was aimed at finding the barriers that prevent sexual seed production, based on detailed embryological analyses of the whole generative cycle, including microsporogenesis, pollen viability, megasporogenesis, female gametophyte development, and embryo and endosperm formation. Sterility of M. ×giganteus results from abnormal development of both male and female gametophytes. Disturbed microsporogenesis (laggard chromosomes, univalents, micronuclei) was further highlighted by low pollen staining. The frequency of stainable pollen ranged from 13.9% to 55.3% depending on the pollen staining test, and no pollen germination was observed either in vitro or in planta. The wide range of pollen sizes (25.5-47.6 μm) clearly indicated unbalanced pollen grain cytology, which evidently affected pollen germination. Only 9.7% of the ovules developed normally. No zygotes nor embryos were found in any analyzed ovules. Sexual reproduction of M. ×giganteus is severely hampered by its allotriploid (2n=3x=57) nature. Hybrid sterility, a strong postzygotic barrier, prevents sexual reproduction and, therefore, seed formation in this taxon

Effects of zearalenone and 24-<i>epi</i>brassinolide on the salt tolerance of select monocotyledonous crop plants

Salinity has an increasing impact on crop production worldwide. Contemporary agricultural practices increasingly use plant biostimulants that protect plants against various environmental stresses. The aim of the work was to investigate whether such stimulants as 24-epibrassinolide (EPI) and zearalenone (ZEN) may alleviate effects of salinity in bread and durum wheat, maize, and sorghum plants. Plants were grown in glasshouse, in pots filled with perlite under continuous salinity stress (120 mM of NaCl). Four-week-old plants were treated with the stimulants. The plant responses to salinity were determined analyzing the following parameters: fresh and dry weights of plants, water content, electrolyte leakage, proline, abscisic acid, and the soluble carbohydrate contents in the leaves. The positive effect of ZEN on the studied parameters was more frequently observed than in the case of EPI. ZEN increased the root mass of both wheat species, as well as the stem and root masses of sorghum. This stimulant improved water relations in bread and durum wheat. Both stimulators increased the content of soluble carbohydrates. ZEN elevated significantly abscisic acid content in sorghum plants as well as it increased strongly proline level in all studied plant species. ZEN was more effective in alleviation salinity disorders than EPI.

Embryological background of low seed set in distylous common buckwheat (Fagopyrum esculentum Moench) with biased morph ratios, and biostimulant-induced improvement of it

The biased ratio (1:2.7 - 1:19) of long-styled Pin and short-styled Thrum flowers (anisoplethy) in common buckwheat (Fagopyrum esculentum) with low seed set (9.8-33.1%) is documented for the first time in two cultivars (Kora, Panda) and two strains (PA13, PA14). To establish the reasons for low grain yield we studied pollen, embryo sacs, embryos, counted stigmas with compatible pollen and with compatible pollen tubes, and recorded seed set under semi-controlled conditions with open access of pollinators. We also sought to improve seed yield via exogenous application of eight biostimulants at the beginning of flowering. Pin pollen supply to Thrum stigmas was low, due to the imbalance of flower morphs. This did not affect seed set or male success in either flower morph. The pollen of Pin or Thrum was highly viable (97.9-99.9%) in all studied cultivars and strains, germinating well on compatible stigmas. The female success of both flower types was much lower; 49-59% of the ovules exhibited signs of degeneration (whole flower buds, ovules only) or abortion (mature embryo sacs, proembryos, embryos); the highest share of mature embryo sac abortions resulted from degeneration of synergids or the whole egg apparatus. Three biostimulants (Gibberellic acid, putrescine, Asahi SL) in PA13 and six (1-Naphthaleneacetic acid, Gibberellic acid, TYTANIT, putrescine, 6-Benzylaminopurine, Asahi SL) in PA14 decreased embryo abortions (4-12 fold) and increased seed set (0.4-2.4 times), but seed set was still low and never exceeded 33% (the highest value of the untreated with biostimulants plants). Biostimulant treatments were most effective on PA14 strain increasing seed set in 7 out of 8 treatments. These were Gibberellic acid, putrescine and Asahi SL improving seed set of two among four analysed genotypes