Browse results

Rotem Fratkin Segman, Zvy Dubinsky and David Iluz

ABSTRACT

Since the Industrial Revolution, increasing atmospheric CO2 has been causing a rise in the concentration of carbon dioxide dissolved in seawater. This process results in seawater acidification, which has a major impact on the physical and chemical parameters of the oceans, consequently affecting the numerous calcifying organisms in the marine environment. Calcifying organisms secrete calcium carbonate in their inner or outer skeleton and include plankton (e.g. coccolithophores and foraminifera), corals, mussels and some of the macroalgae. Calcifying macroalgae make a critical contribution to the structure and function of marine ecosystems in several coastal biotas, providing food and shelter to diverse organisms. The present review summarizes the current information about the brown alga Padina sp. and its ecophysiology, focusing on the environmental control of the calcification process; suggests possible benefits that seaweeds may derive from their calcium carbonate cover, and discuss different future Intergovernmental Panel on Climate Change scenarios of ocean acidification and their likely impact on calcifying algae and on the ecosystems in which they are a key component.

Namita Bhutani, Rajat Maheshwari, Monika Negi and Pooja Suneja

Endophytic bacteria isolated from nodules of Vigna radiata were screened for indole acetic acid (IAA) production. Three isolates MBN3, MJHN1 and MJHN10, molecularly identified as Bacillus aryabhattai (MF693121.1), B. megaterium (MF693120.1) and B. cereus (MF693119.1) were producing significantly high amount of IAA. Production parameters viz. L-tryptophan concentration, incubation time, carbon and nitrogen sources were optimized. The study revealed the presence of trp-dependent pathway for IAA production in the isolates. All of them gave maximum production with yeast extract as nitrogen source but variation in preference for carbon sources was observed. The invitro application of bacterial isolates on plant roots resulted in increase in root length as well as number of lateral roots. These results confirm the occurrence of Bacillus as predominant non-rhizobial endophytic genera in summer season crop and its potential as plant root growth promoter.

Nirit Bernstein, Mollie Sacks, Piny Snir and Rivka Rosenberg

Ca deficiencies induce a range of physiological disorders in plants. The disorders typically appear in young growing tissues that are characterized by high demand for Ca and restricted Ca supply due to low transpiration. In this study, we examined the effect of supplementing Ca by foliar spray and through the irrigation solution to Anemone coronaria plants, in order to evaluate if flower abortions and leaf damages that appear in the production fields are related to Ca deficiencies. With the goal to develop a preventive nutritional regime, four Ca treatments were evaluated. The supplemented Ca was applied with the fertigation solution in the concentrations of 60 or 110 ppm Ca; with the 60 ppm application an additional application of Ca by foliar application was tested in concentrations of 3 g/l Ca or 6 g/l Ca, as Ca(NO3)2. The plants were cultivated in a net-house, in soilless culture (Tuff) beds. Application of 110 ppm Ca compared to 60 ppm with the fertilizing solution increased the concentration of Ca in the leaf tissue, resulting in an increase in the quantity and quality of the flowers. Calcium supply by foliar spray, at both 3 g/l or 6 g/l Ca(NO3)2 caused leaf necrosis and did not improve yield production. Application of 110 ppm Ca reduced the concentrations of Mn, Cl and Na in the leaves. Application of Ca in the irrigation solution, or by foliar spray, did not reduce the percentage of non-marketable flowers. The identified lower concentrations of Ca in damaged compared to non-damaged leaves on the flower stem suggests that the damages to the flowers and the leaves is related to local deficiencies of Ca.

Kiran S. Khandagale, Rahul L. Zanan and Altafhusain B. Nadaf

ABSTRACT

Rice (Oryza sativa L.) is one of the most important food crops. Various conventional and modern techniques have been employed for improvement in rice. RNA interference (RNAi) is one of the popular reverse genetic strategies being practiced among plant scientists due to its efficiency and specificity. Nowadays, new age-targeted genome editing tools such as transcription activator-like effectors nucleases (TALEN) and clustered regularly interspaced palindromic repeats (CRISPR/Cas) are becoming popular due to their ability of precise modification of genome sequence and regulation of gene expression patterns in a site-specific manner. Here, we reviewed the utility of RNAi, TALEN and CRISPR/Cas in various aspects of rice improvement such as plant architecture, plant development, biotic and abiotic stress tolerance and qualitative improvement. A comparison of RNAi and targeted genome editing methods will provide some insights for researchers working on improvement of rice.

Guangfu Zhang and Rui Yao

ABSTRACT

Spinescence (including spines, thorns, and prickles) plays an important role in defense from herbivores. To examine whether spinescence evolved at random or differently in various life forms, plant organs, and aquatic taxa at the level of families, we analyzed the characteristics of wild spinescent aquatic plant species in the Yangtze Delta, East China. There were 92 such species, belonging to 33 genera and 21 families out of 203 wild aquatic vascular macrophyte species. Reproductive structures (including flowers, seeds, fruits and appendages) were well defended in the majority of aquatic plants compared with vegetative organs, especially for emerged macrophytes, probably resulting from the selective pressure from herbivores. Overall, most of the aquatic plants (67 species, 62.0% of the total number of species) had spiny reproductive structures while the others (41 species, 38.0% of the total number of species) had spiny vegetative organs, mostly in leaves, and only a few had thorny or prickly stems. In terms of spinescent aquatic species, there were significant differences among various life forms. Emerged macrophytes had 63 species, accounting for 58.3% of the whole; furthermore, the majority of such species (i.e. 42) were spinescent in reproductive organs. In contrast, the number of spiny floating and submerged plant species was eight and 37, respectively. It is noted that some families had more spiny species than others, especially the Cyperaceae and Najadaceae, which mainly defended their reproductive organs. Therefore, like terrestrial flora, aquatic plants also evolved spinescence as a defense against herbivores.

Anam Moosa, Ayaz Farzand, Shahbaz Talib Sahi and Sajid Aleem Khan

ABSTRACT

Being sessile organisms, plants are continuously challenged by phytopathogenic fungi, contributing the largest share in loss due to plant disease. Plants naturally possess a well-developed and programmed protein-based defense system, capable of producing antimicrobial cationic peptides to ward off pathogen attack. Numerous genes encoding antifungal proteins have been isolated, cloned, sequenced and transgenically expressed against multiple phytopathogenic fungi successfully. Genetic engineering technology has been widely utilized to produce transgenic plants with enhanced resistance against pathogens. Pathogenesis-related proteins (PR-proteins) is a group of the most important inducible defense-related antifungal proteins, including defensins, thionins, osomtin-like proteins, thaumatin-like proteins, chitinases, glucanases, oxalate oxidase or oxalate oxidase-like proteins and lipid transfer proteins. Transgenic plants have been developed by imparting the artificial expression of genes encoding antifungal PR-proteins. The expression of transgenes belonging to a single group of PR-proteins or synergistic action of transgenes from different groups has greatly uplifted the level of defense response in plants against fungi. Transgenic expression of antifungal PR-proteins has led to remarkably enhanced resistance in transgenic plants. In this review, we have summarized the role of PR-proteins in plant defense against fungi and 15 years of success achieved so far to generate a variety of transgenic plants resistant against fungi through overexpression of transgenes from different groups of PR-proteins.

Zorica Kotur, Shiela E. Unkles and Anthony D. M. Glass

The high-affinity nitrate transporter of green plants is composed of two polypeptides, NRT2.1 and NAR2.1, while in fungi it appears that nitrate influx is mediated by NRT2 alone. Another difference between plants and fungi is that the central (cytoplasmic) loop of the 12 membrane spanning regions of NRT is quite large in fungi, consisting of 91 amino acid residues, compared with the relatively short (21 amino acid residues) plant NRT2.1. Here we examine potential amino acid residues involved in the plant NRT2.1:NAR2.1 association by mutation of conserved amino acids in Arabidopsis thaliana AtNRT2.1. Only the replacement of leucine 85 by glutamine disrupted the association between AtNRT2.1 and AtNAR2.1, as examined using the yeast two-hybrid system. Further, to investigate the nitrate-transporting function of AtNRT2.1 in a context free of other members of the NRT2 family, we expressed AtNRT2.1 in Aspergillus nidulans. In the fungal context the plant NRT alone was capable of restoring nitrate transport to a nitrate transport defective mutant, but only when the AtNRT2.1 central loop was replaced by its fungal counterpart.

Benayahu Bar-Yosef

Long-term application of fertilizer and manure may change soil fertility, crop yield, N uptake efficiency, and nitrate and chloride leaching to underground water. The objectives were to quantify those aspects in a long-term (35-year) permanent plots field experiment in a typical arid zone (~250 mm rain) soil, and suggest fertilization and manuring regimes leading to reduced aquifer pollution by nitrate and chloride without compromising crop yield and soil sustainability. Results proved that mineral-N application exceeding plant demand leached, subject to recommended irrigation plus rainfall, below 4 m, thus becoming a potential underground water pollution hazard. Leaching was significantly reduced by partially replacing fertilizer-N by manure-N, with negligible adverse effect on crop yield. Under ample manure (M2) and mineral N (N3) supply (treatment M2N3), the estimated cumulative (35-year) NO3 leaching was 557 g N/m2 and the corresponding Cl leaching 4097 g Cl/m2. In treatment M2N0 the corresponding leaching was 0 and 4135 g/m2. The cumulative solute leaching depth was estimated to be 66 m in treatment M2N3 (that gave maximum fruit and dry matter yield) and 125 m in treatment M0N0 (minimum fruit and dry matter yield). Soil cultivation and cropping for 35 years had negligible effect on the plants’ response to fertilizer level and on the soil mineralogical composition.

Mollie Sacks, Uzi Kafkafi, Ofra Ziv, Shoshana Salim, Shimon Meir, Sonia Philosoph-Hadas, Elisha Kenig, Yair Tamari, Roberto Natan, Eitan Shlomo and Joseph Riov

The irrigation and fertilization regime of different varieties of Grevillea in Israel are based on existing knowledge for growing various varieties of the Proteaceae family for production of cut flowering branches. However, growers face problems in cultivating Grevillea “Spiderman,” such as leaf chlorosis, prolonged growth until flowering, and reduced quality of cut flowering branches. The present study aimed to examine whether these problems stem from deficiency or excess of Fe, Mn, Zn, P, and Mg, focusing on the effect of these nutrients on growth, flowering, and appearance of visual leaf symptoms and on yield, quality, and vase life longevity of cut flowering branches. The nutrient treatments significantly affected plant development and flowering. Increasing the Fe concentration from 1 to 2 or 3 mg l–1 resulted in improved leaf color, from slightly yellow to dark green. The combination of 2 mg l–1 Fe + 1.8 mg l–1 Mn resulted in early flowering, highest yield, and development of long lateral branches. Low levels of P caused in the first year of treatment leaf chlorosis, which was intensified during the third year, resulting in severe yellowing of the flowering branches. Leaf necrosis and tip burn appeared in treatments with high concentrations of Zn, Mn, and Mg. Deficiency of Fe and Mn and high concentration of P and Mg led to the development of a large number of branches without flowers. The optimal fertilization treatment that yielded the highest quality of flowering branches after harvest was 2 mg l–1 Fe. Branches of this treatment had green foliage at harvest and the longest vase life (10 days) following the recommended postharvest treatment and air transport simulation. Based on the findings of the present research, it can be concluded that the problems in the cultivation of G. “Spiderman,” such as leaf chlorosis, delayed flowering, and reduced quality of flowering branches, result from improper fertilization.

Nirit Bernstein and Uri Yermiyahu