| Heilongjiang Province is located in the alpine region of our country, the main cultivated in the mining waste wasteland, mountains, the fields, and poor soil. Much more national preferential policies had been to speed up the development of sericulture industry in northern cold regions. Mulberry cultivation farms to transfer to field cultivation. Heilongjiang Province is one of the most suitable for the development of sericulture production areas in China, silkworm has become the pillar industries in the western arid, semi-arid areas of Heilongjiang Province, especially the cultivation of mulberry varieties "Long Sang NO.1" born accelerate the region the rapid development of the silkworm industry. However, in the actual production, in order to obtain a higher yield of mulberry leaves, some silkworm breeder fails to soil nutrient status and mulberry Fertilizer Demand Rule of unlimited increase the amount of nitrogen fertilizer, which will not only fail to improve the mulberry leaf yield, but increased input costs, environmental pollution, resulting in the decline in the quality of sericulture. Leaves of mulberry are harvested object crop cultivation its main purpose is to obtain high yield blade, while nitrogen is a very important factor. To this end, the departure from Nitrogen Fertilizer in Heilongjiang Province mulberry cultivation process, through the years (2009-2012) multi-point (Harbin, Cheng, Jiamusi) test in determining the nitrogen amount in the range of the main cultivated varieties of mulberry based on the use of mulberry nitrogen forms (nitrate and ammonium nitrogen) through field trials and hydroponics method of combining production from the material-the light reactions of photosynthesis and dark reaction between synergy angle, in-depth analysis of the response characteristics of the mulberry nitrogen. The results are as follows:1. In order to research the best appropriate N application levels of "Longsang No.1" and "qinglong", and support a optimum guide for mulberry peasant, this study was carried out to investigate the effects of different N application levels (0,48.3,96.6,144.9,193.2and241.5kg·hm-2pure nitrogen) and (0kg·hm-2,13.8kg·hm-2,27.6kg·hm-2,41.4kg·hm-2,55.2kg·hm-2,69kg·hm-2) on growth and physiological characteristics of mulberry grown in the field using mulberry variety Longsang No.l and "qinglong" as experimental material. The results showed that leaf number, branch number, leaf area, leaf weight and leaf yield per plant increased with nitrogen application levels in0～193.2and kg·hm-20～55.2kg·hm-2, while the nitrogen application levels in241.5kg·hm-2and69kg·hm-2, the leaf area, leaf weight and leaf yield per plant reduced. Total nitrogen and total phosphorus contents in leaves of mulberry increased with nitrogen application levels in0～144.9kg·hm-2and41.4kg·hm-2, but over nitrogen application levels of that the trend is opposite, the indicating that higher nitrogen can be reduce the absorption of N and P. Chlorophyll, soluble protein contents and soluble sugar contents in leaves of mulberry increased with nitrogen application levels increased. In sum, by the N application levels on the growth and physiological characteristics of mulberry, the best N application levels in the field of "Long sang NO.1" and "qinglong" is144.9～241.5kg·hm-2and41.4～55.2kg·hm-2respectively. Nitrogen fertilizer and mulberry leaf yield amount (Y) in a four-year field experiment partial least squares regression model are as follows:y=1552.3484111+2.702975x1+58.083982x2+9.429218x3-0.000561x1*x1-0.672614x2*x2-0.017726x3*x3-0.036371x*x2-0.005904x1*x3-0.109191x2*x3y=1450.0240821+2.983592x1+54.401789x2+9.645707x3-0.001892x1*x1-0.579893x2*x2-0.018230x3*x3-0.032356x1*x2-0.005737x1*x3-0.102818x2*x3y=1490.3531551+2.752968x1+51.050728x2+8.862974x3-0.001686x1*x1-0.544203x2*x2-0.016403x3*x3-0.030354x1*x2-0.005270x1*x3-0.094480x2*x3y=608.0876801+4.590733x1+37.395394x2+5.491631x3-0.003846x1*x1-0.483353x2*x2-0.010424x3*x3-0.070032x1*x2-0.010284x1*x3-0.070982x2*x32. The effects of different proportions of nitrate and ammonium nitrogen applied to mulberry (Morus alba L.) on plant growth and photosynthetic characteristics of mulberry seedlings cultured in hydroponics were investigated under the same nitrogen amount using forage mulberry variety "Qinglong" as experimental material. Plant height, leaf number, leaf area and root length of mulberry seedlings grown in hydroponics of single ammonium or nitrate nitrogen source were lower than that of proportion solution of ammonium and nitrate nitrogen, leaf and root biomass of mulberry seedlings grown in hydroponics was similar trends. Plant growth and biomass in mulberry seedlings were highest while the proportions of nitrate and ammonium nitrogen were50:50and25:75. Net photosynthetic rate (Pn), stomatal conductance (Gs) and water use efficiency (WUE) in leaves of mulberry seedlings cultured in25:75proportion solution of ammonium and nitrate nitrogen were higher than that of other proportion treatments. Single ammonium or nitrate nitrogen source improved the apparent quantum efficiency (AQE) and decreased light compensation point (LCP) in leaves of mulberry seedlings. It concluded that forage mulberry varieties "Qinglong" prefer nitrate nitrogen, and the proportions of nitrate and ammonium nitrogen adapted mulberry growth were between50:50and25:75.3. In three different nitrogen treatments, the chlorophyll content (Chl), photosyntheticRate (Pn), RuBPcase initial activity, RuBPcase content, mesophyll conductance (gm), carbonic Anhydrase (CA) activity, PS1activity and PS1activity of leaves were the highest in the mixture treatment of NH4++NO3-, then were in the NO3-treatment and the lowest were in NH4+treatment. No evident differences were found in RuBPcase specific activity among treatments. There was little difference on stomatol conductance (Gs) between different treatments and CK. Nitrogen nutritions decreased the intercellular CO2concentration (Ci). There were similarly Changing trends between gm, CA activity and photosynthetic rate (Pn) in different treatments, Which showed the conductivity of CO2in liquid part of mesophyll cell having probably important Influence on photosynthesis of leaves. Compared to NH4+treatment, NO3-treatment increased the photorespiration rate, the ratio of photorespiration rate to photosynthetic rate and nitrate reduetase (NR) activity in wheat leaves. The increase of photosynthetic rate in mixture treatment NH4++NO3-was mainly correlated to the higher Rubisco activity, higher photosynthetic electron conductivity and the improvement of CO2conductivity in liquid phase of mesophall cell.4. Nitrogen plays an important role throughout the whole life of all living organisms. Nitrate and ammonium are the major forms of nitrogen available to plants. Though both forms can be utilized, great differences in plant growth are found among various plants. Since1950s many research efforts have been directed toward unraveling the causes and mechanisms of NH4+toxicity as well as the relationship of nitrate and photoprotection in plants, while present knowledge is far from complete. It is kown that most of the energy for nitrate assimilation in a cell derives from photosynthesis. Recently, nitrate reduction has been suggested to be involved in the photo protection mechanism. However, our present understanding of this role of nitrate is poor. This research focuses on the difference in allocation. The results are as follows:1) The effects of different nitrogen forms on biomass and gas exchange of mulberry and rice were studied. Ammonium significantly decreased both shoot biomass and root biomass of mulberry, especially root biomass. Photosynthetie rate (Pn) of mulberry under ammonium condition was also significantly lower than those under nitrate condition while stomatal conductance and intracellular CO2concentration were higher. Thus, decreased Pn could be attributed to stomatal limitation. In comparison, there were no significant differences in biomass and gas exchange between rice cultured under nitrate or ammonium condition.2) The effects of different nitrogen forms on photosynthetic electron allocation and nitrate reduetase activity were investigated in mulberry and rice plants. When cultured with ammonium as nitrogen source, mulberry plants had lower JF(PS Ⅱ)), Jo(PCR), JC(PCO. The effects of different nitrogen forms on chlorophyll fluorescence and xanthophyll cycle activity were studied in mulberry and rice plants. There was no significant difference in either chlorophyll fluorescence or xanthophyll cycle activity between nitrate and ammonium feed rice plants.5. The responses of photosynthetic electron transport and excitation energy distribution in winter wheat leaves at the jointing stage to nitrogen levels were studied in the field experiment, both leaf gas exchange parameter and chlorophyll fluorescence were measured. The light energy absorbed by antenna pigment of both cultivars increased with the treatment of nitrogen. Although nitrogen could not obviously change the distribution proportion of photosynthetic carbon reduction and photosynthetic carbon oxidation, nitrogen could increase JF of PSII and photosynthetic rate. Nitrogen could affect PSII activities of both cultivars, and there were significant differences between the two cultivars. Nitrogen application improved the competition between heat dissipation and photo-chemic reaction and enhanced the self-protection ability of photosynthetic apparatus.In summary, the regulation mechanism of growth of mulberry trees from nitrogen and nitrogen forms, the mulberry leaf photosynthetic electron transport and absorption of light energy distribution characteristics for clues to reveal the nitrogen, especially of nitrogen forms in Mulberry metabolism processsource of reducing power (NADPH or NADH) to clarify the reducing power of nitrate reduction to ammonium nitrogen needs from the photosynthetic electron transport chain (PS I side), but the ammonium nitrogen assimilation into amino acids in plant roots, reducing power mainly from respiration, which proved effective consumption of energy excess the photosynthetic chain electron acceptor library part of the excess excitation energy, thereby reducing the destruction of photoinhibition of photosystem and explain long beencontroversial reduction of nitrate to the contribution of the optical destruction defense mechanism, to help us further understand plant Photoprotective Mechanisms. |
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