Since sweet potato (Ipomoea batatas) produces high yield of storage roots (SR), it is an attractive target for improving productivity. However, molecular information about sweet potato is limited. The number of SR per plants determines the yield of sweet potato. SRs develop from adventitious roots (AR). Therefore, the mechanisms responsible for the initiation and development of AR need to be elucidated to increase the productivity of sweet potato. We conducted a transcriptomic analysis between nodes containing AR primordia (AR-node) and stems using next-generation sequencing to identify AR-specific promoters. A total of 6,219 contigs exhibited stronger expression in the AR-nodes than in the stems. Among them, we found that the expression of sweet potato Plant AT-rich sequence- and zinc-binding protein (IbPLATZ) transcription factors was AR-specific. We examined the promoter activity of IbPLATZ in the transgenic Arabidopsis plants. β-glucuronidase (GUS) staining showed that the IbPLATZ promoter conferred the expression of the GUS reporter gene in a root tip-specific manner. These results indicate that the IbPLATZ promoter is available for a root tip-specific foreign gene expression system in transgenic plants.

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In this study we analysed changes in distribution and morphological properties of fine roots caused by underplanting of a 110-year-old Norway spruce monoculture by silver fir and common beech. Three different stand structures were investigated: mature spruce underplanted by beech (S/b), by fir (S/f) and mature spruce with natural regeneration of spruce (S/s). We established 3 sample plots per each structure and took 5 soil cores per sample plot (45 cores in total). Soil cylinders of 5 cm diameter were taken up to 40 cm depth. Fine roots (diameter ≤ 2 mm) were extracted from the soil, classified according to tree species, weighted and scanned; their length and surface were quantified and specific root length (SRL) and specific surface area (SSA) were calculated. Root-to-root interaction of spruce and underplanted species led to differences in vertical distribution of roots towards the more homogenous root density in investigated profile with clear shifting of beech and fir roots into deeper soil layers. Cumulative root fractions of fir and beech in upper 20 cm were lower than those of Norway spruce. The share of spruce roots in depth under 20 cm never exceeded 20%. The co-occurrence of beech and spruce in small spots was about twice as frequent as the co-occurrence of spruce with fir. We found differences in SRL and SSA between broadleaves (beech) and conifers, while the values of beech morphological parameters increased significantly, when mixed with spruce. We assume that the competitive strategy of beech is based in changing its root morphology, whereas silver fir is inclined to extend its biomass.

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Thidiazuron (TDZ), a well known plant growth regulator is used in tissues culture as a supplement to the basal MS medium. Several reports suggest the role of TDZ in promoting plant organogenesis and plant regeneration. Our experiments to micropropagate the sugarcane using various growth regulators reveal the role of TDZ in rooting and survival of a high yielding new sugarcane variety Co 05011. Various permutation combinations were tried using TDZ as the main regulator to rapidly increase the number of plantlets. Shoot cultures were repeatedly multiplied for 10 cycles and then transferred to MS medium augmented with various concentration of TDZ along with 1-naphthylacetic acid (NAA) and sucrose for rooting. Results of present study indicate optimum concentration of TDZ (0.002 mg/L) in combination with NAA (0.5 mg/L) resulted in 93.6% root formation. Moreover, when these shoots were re-cultured in the same media for another two cycles it produced 100% rooting and had almost 100% survival during acclimatization. These results indicate that TDZ and NAA combination enhance the activity of NAA and resulting in massive proliferation of roots. TDZ increases the frequency and proliferation of healthy and vigorous roots in micropropagated shoots thus enhancing their survival rate in field and during hardening process. This work can be helpful in developing successful and cost effective tissue culture of elite sugarcane varieties.

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Hop cones are an indispensable raw material used for beer brewing. Since the hop plant is a minor crop, expansion habit of the hop root system has not been well investigated. In this study, we observed and analyzed the root systems of two major hop cultivars in Hokkaido, Little Star and Furano Special, using the wall profile method and root depth index. The results suggest differences in expansion habit of the hop root between the two hop cultivars, which has not been reported previously. The results also indicate that the different responses in cone yield to precipitation between the two hop cultivars may be derived from their differences in root expansion habit. The results of this preliminary study support the view that a better understanding of the hop root system could lead to improved productivity of hops via the development of agronomical techniques or genotypes.

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Legumes are very important plants both ecologically and agriculturally because they are able to interact symbiotically with rhizobia for biological nitrogen fixation and soil fertilization. Medicago truncatula Gaertn. is an important model legume rich in protein. Salinity represents, today, the major cause of land degradation and crop productivity limitation around the world and affects physiology and metabolism in legumes. In this study, we analyzed the physiological and biochemical responses of rootlets in two contrasting ecotypes of Medicago truncatula (Tru 131, tolerant and Jemalong, sensitive) to different level of NaCl, (68, 102 and 137 mM). Results showed that the tolerant ecotype has a lower water potential than Jemalong. Root protein content of Tru 131 was decreased than Jemalong, this can be explained by accumulation of protein oxidation in the sensitive genotype. Moreover, NaCl increased guaiacol peroxidase activity GPX in rootlets of Tru 131, this enzyme has a protective role against the molecules ROS accumulated during oxidative stress. On the other hand, under salt stress the total content of ascorbate (ASC + DHA) and Glutathione (GSH + GSSG) was increased in the tolerant genotype Tru 131 compared to Jemalong. These results show how the tolerant genotype activate the antioxidative defense system at root level against damages caused by oxidative stress under salinity.

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