As the result of intensive research and breeding efforts over the last 20 years, the yield potential and yield quality of cereals have been greatly improved. Nowadays, yield safety has gained more importance because of the forecasted climatic changes. Drought and high temperature are especially considered as key stress factors with high potential impact on crop yield. Yield safety can only be improved if future breeding attempts will be based on the valuable new knowledge acquired on the processes determining plant development and its responses to stress. Plant stress responses are very complex. Interactions between plant structure, function and the environment need to be investigated at various phases of plant development at the organismal, cellular as well as molecular levels in order to obtain a full picture. The results achieved so far in this field indicate that various plant organs, in a definite hierarchy and in interaction with each other, are involved in determining crop yield under stress. Here we attempt to summarize the currently available information on cereal reproduction under drought and heat stress and to give an outlook towards potential strategies to improve yield safety in cereals.

https://onlinelibrary.wiley.com/doi/pdf/10.1111/j.1365-3040.2007.01727.x

The effect of drought and heat stress on reproductive processes in cereals.

https://pubag.nal.usda.gov/pubag/downloadPDF.xhtml?id=21001&content=PDF

Species, ecotype and cultivar differences in spikelet fertility and harvest index of rice in response to high temperature stress

http://directory.umm.ac.id/Data%20Elmu/jurnal/P/PlantScience/PlantScience_Elsevier/Vol150.Issue1.2000/5209.pdf

myo-Inositol metabolism in plants

The reproductive (gametophytic) phase in flowering plants is often highly sensitive to hot or cold temperature stresses, with even a single hot day or cold night sometimes being fatal to reproductive success. This review describes studies of temperature stress on several crop plants, which suggest that pollen development and fertilization may often be the most sensitive reproductive stage. Transcriptome and proteomic studies on several plant species are beginning to identify stress response pathways that function during pollen development. An example is provided here of genotypic differences in the reproductive stress tolerance between two ecotypes of Arabidopsis thaliana Columbia (Col) and Hilversum (Hi-0), when reproducing under conditions of hot days and cold nights. Hi-0 exhibited a more severe reduction in seed set, correlated with a reduction in pollen tube growth potential and tropism defects. Hi-0 thus provides an Arabidopsis model to investigate strategies for improved stress tolerance in pollen. Understanding how different plants cope with stress during reproductive development offers the potential to identify genetic traits that could be manipulated to improve temperature tolerance in selected crop species being cultivated in marginal climates.

Temperature stress and plant sexual reproduction: uncovering the weakest links

A very important mineral storage compound in seeds is phytate, a mixed cation salt of phytic acid (myo-inositol hexakis phosphoric acid). This compound is important for several reasons: (1) It is vital for seed/grain development and successful seedling growth. (2) It is often considered to be an antinutritional substance in human diets, but it may have a positivenutritional role as an anti-oxidant and an anti-cancer agent. (3) It represents a very significant amount of phosphorus being extracted from soilsand subsequently removed with the crop. (4) It plays a role in eutrophication of waterways. A key part of this review is an estimate of the annualtonnage of phosphorus and phytic acid sequestered in up to 4.1 billion metric tonnes of crop seeds and fruits globally each year. We estimate thatnearly 35 million metric tonnes of phytic acid, containing 9.9 million metric tonnes of P, is combined with about 12.5 and 3.9 million metric tonnes of K and Mg respectively, to form each year over 51 million metric tonnes of phytate. The amount of P inthis phytate is equal to nearly 65÷ of the elemental P sold world wide for use in mineral fertilizers. Dry cereal grains account for 69÷ of the total crop seed/fruit production but account for 77÷ of the total phytic acid stored each year. Low phytate mutants, that are now available for some key staple food crops such as maize and barley, offer potential benefits in such areas as the sustainability of lands used to grow crops, the mineral nutrition of humans and animals, and reduction in pollution of waterways.

https://www.cambridge.org/core/services/aop-cambridge-core/content/view/S0960258500000039

Phytic acid and phosphorus in crop seeds and fruits: a global estimate.

Myo-inositol-1-phosphate (I[1]P) synthase (EC 5.5.1.4) catalyzes the reaction from glucose 6-phosphate to I(1)P, the first step of myo-inositol biosynthesis. Among the metabolites of I(1)P is inositol hexakisphosphate, which forms a mixed salt called phytin or phytate, a storage form of phosphate and cations in seeds. We have isolated a rice (Oryza sativa L.) cDNA clone, pRINO1, that is highly homologous to the I(1)P synthase from yeast and plants. Northern analysis of total RNA showed that the transcript accumulated to high levels in embryos but was undetectable in shoots, roots, and flowers. In situ hybridization of developing seeds showed that the transcript first appeared in the apical region of globular-stage embryos 2 d after anthesis (DAA). Strong signals were detected in the scutellum and aleurone layer after 4 DAA. The level of the transcript in these cells increased until 7 DAA, after which time it gradually decreased. Phytin-containing particles called globoids appeared 4 DAA in the scutellum and aleurone layer, coinciding with the localization of the RINO1 transcript. The temporal and spatial patterns of accumulation of the RINO1 transcript and globoids suggest that I(1)P synthase directs phytin biosynthesis in rice seeds.

/pdf/temporal-and-spatial-patterns-of-accumulation-of-the-4l5rss15gb.pdf

Temporal and Spatial Patterns of Accumulation of the Transcript of Myo-Inositol-1-Phosphate Synthase and Phytin-Containing Particles during Seed Development in Rice

An efficient and novel method of direct shoot regeneration from root tips in garlic was developed. The influence of growth regulators, basal media and age of root explant on shoot initiation and proliferation was examined. The best growth regulator combination was 1-naphthaleneacetic acid and 6-benzyladenine at 1 and 10 µM, respectively, inducing shoot initiation from 75% of the explants. The frequency of shoot initiation on different basal media was similar. Explant root tips from plantlets taken 15 to 18 days after sprouting showed the highest shoot initiation (95%). In contrast to Murashige and Skoog medium, which produced more than 10 shoots per explant, B5 medium produced smaller shoots, although the number was higher. Rooting of individual shoots was induced after transfer to medium without growth regulators. Plantlets, after acclimatization in a growth cabinet, were successfully transplanted to the field, and no phenotypic variation was observed among them. The technique has potential applicability for rapid propagation of garlic.

/pdf/high-frequency-shoot-regeneration-and-plantlet-formation-33wlmxw8ju.pdf

High frequency shoot regeneration and plantlet formation from root tip of garlic

Sexual organogenesis in spikelets of rice (Oryza sativa L. cv ‘Kinmaze’) affected by heat stress was investigated using SEM and stereo-microscopy. Of the 243 spikelets dissected, 55.6% developed pistil hyperplasia, i.e., proliferated female organs or tissues, including multiple stigmata and/or ovaries, outgrowth of swollen parenchymatous tissues from inside the ovule, and differentiation of trichomes from ovary epidermis. Conversely, 7% of the spikelets exhibited stamen hypoplasia, represented by a decrease in the number of stamens, and only 3.7% of the spikelets showed hyperplasia, represented by an increase in the number of stamens. The morphological and structural development of the anther was disturbed, and microsporogenesis was inhibited. The shape of the anther was altered, though not perfectly, into the form of an ovary; the lemma and palea changed in form and ultimately resembled each other in shape and size. All of these changes in structure are more or less similar to those that usually result in rice spikelets subjected to cold and other environmental stresses. It was therefore concluded that rice plants show similar responses in sex differentiation in the spikelet under various environmental stresses.

Pistil hyperplasia in rice spikelets as affected by heat stress

Trehalase from the bean-shaped accessory glands of the male mealworm beetle, Tenebrio molitor, was purified by acid treatment, with subsequent chromatography on columns of DEAE-cellulofine and Sephacryl S-300. The molecular masses of the native and the denatured forms were estimated to be 43 and 62 kDa by gel filtration and SDS-PAGE, respectively, an indication that the trehalase may be composed of a single polypeptide. The optimum pH of the reaction catalyzed by trehalase was 5.6–5.8. The Km for trehalose was 4.4 mmol·l−1. Immunohistochemical experiments with trehalase-specific antiserum showed that the enzyme was localized in one specific type of secretory cell in the bean-shaped accessory gland epithelium and within the semisolid secretory mass that was a precursor to the wall of spermatophore. SDS-PAGE and immunoblotting analysis revealed the presence of a polypeptide of about 62 kDa in the spermatophore, Immunohistochemical observations showed that the trehalase was located at the outgrowth in the anterior portion of the spermatophore. When a fresh spermatophore was immersed in phosphate-buffered saline it discharged sperm in the same manner as in the bursa copulatrix of the female. Before the rupture of the expanded bulb of the spermatophore, almost all of the trehalase had dissolved in the phosphate-buffered saline. The addition of validoxylamine A to the saline, a specific inhibitor of trehalase, did not affect the expansion and evacuation of the spermatophore. These results demonstrate that trehalase, synthesized by a specific type of secretory cell in the bean-shaped accessory gland epithelium, is actively passed into the lumen of the bean-shaped accessory gland and then incorporated into the spermatophore. Trehalase appears to be one of the structural proteins of the spermatophore, although the possibility can not yet be completely ruled out that the trehalase-trehalose system functions for the nourishment and/or activation of the sperm in the bursa copulatrix of the female.

Trehalase in the spermatophore from the bean-shaped accessory gland of the male mealworm beetle, Tenebrio molitor: purification, kinetic properties and localization of the enzyme

Tomikichi Wada

Papers

Temporal and Spatial Patterns of Accumulation of the Transcript of Myo-Inositol-1-Phosphate Synthase and Phytin-Containing Particles during Seed Development in Rice

High frequency shoot regeneration and plantlet formation from root tip of garlic

Pistil hyperplasia in rice spikelets as affected by heat stress

Trehalase in the spermatophore from the bean-shaped accessory gland of the male mealworm beetle, Tenebrio molitor: purification, kinetic properties and localization of the enzyme

Effect of Sodium Chloride on the Panicle and Spikelet Morphogenesis in Rice : II. Developmental morphology of the panicle