The absorption of water from humid air by grass embryos during germination.

Grass embryos possess structures that do not occur in any other flowering plants. Due to the specific embryo structure and position, grass embryo surfaces may be exposed to surrounding air under partial caryopsis-soil contact conditions, but whether caryopses of the grass family (Poaceae) can sense soil air humidity to initiate successful germination under partial caryopsis-soil contact conditions remain unknown. Here, we found that grass embryos have the unique ability to absorb water from atmospheric water vapor under partial caryopsis-soil contact conditions. To absorb atmospheric moisture, grass embryos developed profuse and highly elongated hairs on the embryo surface. These hairs, classically known as coleorhiza hairs, developed only on the embryo surface exposed to humid air, and submergence of the embryo surface inhibited their development. In addition to humid air-dependent development, almost all other developmental features of coleorhiza hairs were substantially different from root hairs. However, coleorhiza hair development was regulated by ROOTHAIRLESS 1. Besides the genetic control of coleorhiza hair development, we also identified how caryopses manage to keep the hairs turgid in natural open environments as the hairs were highly sensitive to dry air exposure. Moreover, we video-documented the regulation of developmental processes. The unique humid air-dependent coleorhiza hair development and their ability to absorb water from water vapor present in microsites or soil air give grasses advantages in germination and seedling establishment. Ultimately, coleorhiza hairs may have contributed to the ecological success of the grass family.

Preferential Geographic Distribution Pattern of Abiotic Stress Tolerant Rice.

Crop productivity and stability of the food system are threatened by climate change, mainly through the effects of predicted abiotic stresses. Despite extensive research on abiotic stress tolerance in the past decades, the successful translation of these research to fields/farmers is scarce. The impelling demand of climate resilient varieties, and the poor translation of research into the field despite the availability of high throughput technologies lead us to critically analyse a neglected aspect of current abiotic stress tolerance research. Although environmental factors play the most important role in the development of adaptive traits of plants, most abiotic stress tolerance research ignores eco-geographic aspects of highly stress tolerant accessions. In this review, we critically examined the geographic distribution pattern of highly tolerant rice accessions of all major abiotic stresses along with one micronutrient deficiency. Remarkably, we identified a shared geographic distribution pattern of highly tolerant accessions for all abiotic stresses including zinc deficiency despite the sparseness of highly tolerant accessions. The majority of these tolerant accessions predominately originated from Bangladesh centred narrow geographic region. We therefore analysed the climatic and agro-ecological features of Bangladesh. Considering the threat of climate change on global food security and poverty, urgent concerted research efforts are necessary for the development of climate resilient rice varieties utilizing the technological advancement, know-hows, and the preferential distribution pattern of abiotic stress tolerant rice.

Rayada specialty: the forgotten resource of elite features of rice.

Crop domestication and thereafter gradual selection or directional breeding have narrowed the genetic diversity of elite varieties and even promoted gathering of deleterious mutations in their stress response mechanisms, whereas local ecotypes, landraces and wild relatives still growing on native environment and preferences keep the genetic diversities for features like stress tolerance. Rayada is such an exceptional ecotype, variant of typical deepwater rice, completely endemic to certain areas of Madhumati river tracts of Bangladesh and still shares some features of wild rices. Multiple physiological features of Rayadas are distinctly different from typical deepwater rice. Tolerance to prolonged flood, submergence and cold are special features along with strong photoperiod sensitivity and lack of dormancy. Moreover, longer root system and prompt recovery capacity make it as an elite resource of stress tolerance. However, it has long been neglected because of mainly its long life cycle and poor yield. This review examines the specialty of Rayada rice and the potential use of its unique traits.

Class III peroxidases are activated in proanthocyanidin-deficient Arabidopsis thaliana seeds.

BACKGROUND AND AIMS: It has previously been shown that proanthocyanidins (PAs) in the seed coat of Arabidopsis thaliana have the ability to scavenge superoxide radicals (O2(-)). However, the physiological processess in PA-deficit seeds are not clear. It is hypothesized that there exist alternative ways in PA-deficient seeds to cope with oxidative stress. METHODS: The content of hydrogen peroxide (H2O2) and its relevance to the activities of superoxide dismutase (SOD), catalase (CAT) and peroxidases was investigated in both wild-type and PA-deficit mutant seeds. A biochemical staining approach was used to detect tissue localizations of peroxidase activities in PA-deficit mutant seeds. KEY RESULTS: PA-deficient mutants possess significantly lower levels of H2O2 than the wild-type, despite their higher accumulation of superoxide radicals. Screening of the key antioxidant enzymes revealed that peroxidase activity was significantly over-activated in mutant seeds. This high peroxidase activity was mainly confined to the seed coat zone. Interestingly, neither ascorbate peroxidase nor glutathione peroxidase, just the guaiacol peroxidases (class III peroxidases), was specifically activated in the seed coat. However, no significant difference in peroxidase activity was observed in embryos of either mutants or the wild-type, although gene expressions of several candidate peroxidases were down-regulated in the embryos of PA-deficient seeds. CONCLUSIONS: The results suggest that enhanced class III peroxidase activity in the seed coat of PA-deficient mutants is an adaptive strategy for seed development and survival.