Differing responses of root morphology and physiology to nitrogen application rates and their relationships with grain yield in rice

Root morphology and physiology influence aboveground growth and yield formation in rice.However,root morphological and physiological differences among rice varieties with differing nitrogen(N)sensitivities and their relationship with grain yield are still unclear.In this study,rice varieties differing in N sensitivity over many years of experiments were used.A field experiment with multiple N rates(0,90,180,270,and 360 kg ha^(-1))was conducted to elucidate the effects of N application on root morphology,root physiology,and grain yield.A pot experiment with root excision and exogenous application of 6-benzyladenine(6-BA)at heading stage was used to further verify the above effects.The findings revealed that(1)under the same N application rate,N-insensitive varieties(NIV)had relatively large root biomass(root dry weight,length,and number).Grain yield was associated with root biomass in NIV.The oxidation activity and zeatin(Z)+zeatin riboside(ZR)contents in roots obviously and positively correlated with grain yield in N-sensitive varieties(NSV),and accounted for its higher grain yield than that of NIV at lower N application rates(90 and 180 kg ha^(-1)).(2)The root dry weight required for equal grain yield of NIV was greater than that of NSV.Excision of 1/10 and 1/8 of roots at heading stage had no discernible effect on the yield of Liangyoupeijiu(NIV),and it significantly reduced yield by 11.5%and 21.3%in Tianyouhuazhan(NSV),respectively,compared to the treatment without root excision.The decrease of filled kernels and grain weight after root excision was the primary cause for the yield reduction.Root excision and exogenous 6-BA application after root excision had little influence on the root activity of NIV.The oxidation activity and Z+ZR contents in roots of NSV decreased under root excision,and the increase in the proportion of excised roots aggravated these effects.The application of exogenous 6-BA increased the root activity of NSV and increased filled kernels and grain weight,thereby reducing yield loss after root excision.Thus,the root biomass of NIV was large,and there may be a phenomenon of"root growth redundancy."Vigorous root activity was an essential feature of NSV.Selecting rice varieties with high root activity or increasing root activity by cultivation measures could lead to higher grain yield under lower N application rates.

Root Morphology and Physiology in Relation to the Yield Formation of Rice

Root system is a vital part of plant and regulates many aspects of shoot growth and development. This paper reviews how some traits of root morphology and physiology are related to the formation of grain yield in rice （Oryza sativa L.）. Higher root biomass, root oxidation activity, and cytokinin contents in roots are required for achieving more panicle number, more spikelets per panicle, greater grain-filling percentage, and higher grain yield. However, these root traits are not linearly correlated with yield components. When these traits reach very high levels, grain filling and grain yield are not necessarily enhanced. High numbers of mitochondria, Golgi bodies, and amyloplasts in root tip cells benefit root and shoot growth and yield formation. Proper crop management, such as an alternate wetting and moderate soil drying irrigation, can significantly improve ultra-structure of root tip cells, increase root length density and concentration of cytokinins in root bleedings, and consequently, increase grain-filling percentage, grain yield, and water use efficiency. Further studies are needed to investigate the mechanism underlying root-shoot and root-soil interactions for high grain yield, the roles of root-sourced hormones in regulating crop growth and development and the effects of soil moisture and nutrient management on the root architecture and physiology.

Hypocotyl elongation based on HY5 transcription factor in cold resistant winter rapeseed(Brassica napus L.)

Winter rape(Brassica napus L.)is better than other edible oil crops in China,but poor cold resistance is the key factor restricting its development.Hypocotyl length was found closely related to cold tolerance.The correlation between hypocotyl length and semi-lethal low temperature was significant,and the highest correlation between hypocotyl length and LT50 of autumn sowing was 0.9557.When the hypocotyl were treated at low temperature,the cells were seriously damaged and formed cavity structures,with cell walls seriously damaged or merged into each other.The positive regulation gene of hypocotyl length in resistant line of VHTSG 10 was identified as HY5(transcription factor HY5-like)by qPCR,and bZIP transcription factor was found to be its conserved domain.Fused gene by GFP and HY5 from VHTSG 10 was transient transferred into Nicotiana benthamiana cells.Corresponding to the 35S:GFP widely distributed in plasma membrane of leaf epidermis,the fusion protein 35S:HY5-GFP was mainly distributed in nucleus.Thus we regarded BnHY5 gene is a key gene related to cold tolerance and hypocotyl length in B.napus.

Morphological and physiological traits of large-panicle rice varieties with high filled-grain percentage

financed by the Special Program of Super Rice of Ministry of Agriculture, China （02318802013231）;the National Public Services Sectors （Agricultural） Research Projects, Ministry of Agriculture, China （201303102）;the Great Technology Project of Ningbo, China （2013C11001）

Marine Green Algae as a Supplement for Chlorophyll and Other Nutrients in Vigna Radiata under UV-C Radiation-Induced Stress

The potential protective effect of marine green algae （Codium iyengerii） was examined in UV-C treated seedlings of Vigna radiata. The study comprises of three treatments of UV-C radiation （100-290 nm） dose for one min in alternative days. This results in deformed morphological parameters, including： decrease in plant height, fresh mass of leaves, shoots and roots, as well as leaf areas, which may be attributed with decreased in the relative growth rate, carbohydrate, amino acids, and protein contents of plant. A drastic effect of UV-C radiation was found on the photosynthetic apparatus where increase in red pigmentations on the leaves surface indicates the presence of UV-C absorbing pigments instead of chloroplast pigments. Visible spectrum of leaves chlorophyll showed reduced concentration of visible absorbing pigments which showed the deleterious effect of these radiations on physiological processes of seedlings. These negative effects of UV-C radiation on plant growth were found to be decreased by the application of green seaweed （Codium iyengerii）, and absorption spectrums of chloroplast contents showed that UV-C radiation inducing damages were appropriately managed by enhanced concentration of seaweeds which significantly increased morphological and physiological parameters like leaf, stem, root biomass, and plant height under UV-C radiation were observed.

Leaf stable carbon isotope composition in Picea schrenkiana var. tianschanica in relation to leaf physiological and morphological characteristics along an altitudinal gradient

To understand the effects of leaf physiological and morphological characteristics on δ13C of alpine trees, we examined leaf δ13C value, LA, SD, LNC, LPC, LKC, Chla+b, LDMC, LMA and Narea in one-year-old needles of Picea schrenkiana var. tianschanica at ten points along an altitudinal gradient from 1420 m to 2300 m a.s.l. on the northern slopes of the Tianshan Mountains in northwest China. Our results indicated that all the leaf traits differed significantly among sampling sites along the altitudinal gradient(P<0.001). LA, SD, LPC, LKC increased linearly with increasing elevation, whereas leaf δ13C, LNC, Chla+b, LDMC, LMA and Narea varied non-linearly with changes in altitude. Stepwise multiple regression analyses showed that four controlled physiological and morphological characteristics influenced the variation of δ13C. Among these four controlled factors, LKC was the most profound physiological factor that affected δ13C values, LA was the secondary morphological factor, SD was the third morphological factor, LNC was the last physiological factor. This suggested that leaf δ13C was directly controlled by physiological and morphological adjustments with changing environmental conditions due to the elevation.