Effects of Low Temperature and Poor Light Environments under LED Lighting on Quality Change of Pepper Seedlings during Storage

Storage and transportation of vegetable commercial seedlings becomes an important link along with the continuous expansion of planting areas of facility vegetables and vegetable seedling culture industry. In this study,pepper variety‘Nongda 24' was as the experimental material,and changes in the morphological and physiological indicators of plug seedlings in different low temperature( 6 and 11℃) and poor light environments were studied to find suitable storage environmental conditions. The results showed that pepper seedlings could be stored and transported for 14 days when storage temperature was 11℃ and light conditions such as light intensity and photoperiod were 30 μmol/( m^2·s)and 12 h/d by using a fluorescent lamp with R∶ B ratio of 1. 9,and 15 μmol/( m^2·s) and 24 h/d by using LED with R∶ B ratio of 1. 3,respectively. Moreover,the quality of pepper seedlings could be protected effectively. Compared to the fluorescent lamp,LED with high luminous efficiency and low energy consumption was suitable for the storage or long-distance transportation of pepper seedlings in low temperature and poor light environments.

Effects of environment lighting on the growth,photosynthesis,and quality of hydroponic lettuce in a plant factory

Leafy vegetable production under controlled environment using artificial lighting has many advantages over conventional greenhouses and open-field production.However,high initial investment and operation costs are restricting the wide application of this technology.In order to design an optimal artificial lighting environment for lettuce production,effects of different combinations of light intensity,photoperiod,and light quality on growth,quality,photosynthesis,and energy use efficiency of lettuce(Lactuca sativa L.cv Ziwei)were investigated under a closed plant factory.Lettuce transplants were grown under photosynthetic photon flux density(PPFD)at 150μmol/m^(2)·s,200μmol/m^(2)·s,250μmol/m^(2)·s,and 300μmol/m^(2)·s provided by fluorescent lamps(FL)with a red to blue ratio(R:B ratio)of 1.8 and light-emitting diode(LED)lamps with R:B ratio of 1.2 and 2.2,in combination with photoperiod of 12 and 16 h/d.In order to examine the“long term”photosynthetic characteristics,net photosynthetic rates of hydroponic lettuce leaves were continuously measured for 2 d(15^(th) and 16^(th) day after transplanting)before harvest.There was no difference in leaf fresh weight(FW)between PPFD of 250μmol/m^(2)·s and 300μmol/m^(2)·s with photoperiod of 16 h/d,regardless of light quality,and same results showed in contents of nitrate,soluble sugar,and vitamin C,respectively.The results of continuous measurements of net photosynthetic rate of lettuce leaves before harvest indicated that plants grown at PPFD of 250μmol/m^(2)·s had consistently higher compared to those grown at PPFD of 300μmol/m^(2)·s.Combining the results from growth,photosynthesis,quality,and energy consumption,it can be concluded that PPFD at 250μmol/m^(2)·s with photoperiod of 16 h/d under LED with R:B ratio of 2.2 is a suitable light environment for maximum growth and high quality of commercial lettuce(cv.Ziwei)production under indoor controlled environment.

Effects of daily light integral on tomato(Solanum lycopersicon L.)grafting and quality in a controlled environment

As the source of energy and biological signals,light can influence the healing process of grafted seedlings by regulating the synthesis of the endogenous hormone,regeneration of wound-healing tissue,and connection of vascular tissue in grafted seedlings.The effect of daily light integral(DLI)on the healing process and seedling quality of tomato(Solanum lycopersicum L.)was analyzed in this study,with the comparison of grafted seedlings treated in dark for 7 d after grafting.The results showed that the height increment of scion and rootstock,adhesion of graft union,stem flow,total chlorophyll content,and net photosynthesis rate increased gradually with increasing light intensity,and no longer increased significantly when the DLI was higher than 5.04 mol/m^(2)·d.The contents of auxin(IAA)and gibberellin(GA)in tomato leaves increased and abscisic acid(ABA)decreased with the increase of DLI.However,there was no significant difference between the treatments with DLI higher than 6.48 mol/m^(2)·d.Both the biomass and energy use efficiency(EUE)of grafted seedlings increased with DLI in a certain range and then decreased.The biomass was the largest when DLI was 5.04 mol/m^(2)·d.However,EUE was highest when DLI was 7.46 mol/m^(2)·d.In conclusion,a suitable DLI is beneficial to cultivate high-quality grafted tomato seedlings,and increasing DLI within a certain range can promote biomass accumulation,connection of vascular tissue,and endogenous hormone biosynthesis in tomato grafted seedlings during the healing period.The lighting environment with DLI of 5.04 mol/m^(2)·d(light intensity of 100μmol/m^(2)·s and light time of 14 h/d)is recommended for the healing treatment in high-quality production,which also improves EUE during the healing period of tomato grafted seedlings.

Estimating EC and ionic EC contribution percentage of nutrient solution based on ionic activity

The dynamic monitoring technology of inorganic ions using ion selective electrodes has some problems such as low precision,vulnerability to other ions,short service life,and high price.Due to the difficulty of dynamic control based on ionic concentration of nutrient solution,EC and pH values of nutrient solution are often used as feedback control indexes in hydroponic system.In this study,estimation algorisms of EC and ionic EC contribution percentage based on ionic activity were proposed to understand the quantitative relationship between ionic concentration and EC.With a view to predicting the EC accurately by mean ionic activities of specific salts in nutrient solution based on a specific formula,ionic concentration could also be calculated by the actual measurement of EC combined with ionic EC contribution percentage.With Japanese horticultural experimental nutrient formula and Yamasaki tomato nutrient formula,significant linear correlations between estimated EC and measured EC were found with determination coefficients over 0.99.Ionic EC contribution percentage was not affected by different relative concentrations of nutrient solutions.However,ionic EC contribution percentage changed significantly when adding specific salts with different concentrations,and different changes were found in each anions and cations of specific salt added.When the same K+concentration was added in different forms of KNO_(3),K_(2_SO_(4),KCl,and KH_(2)PO_(4),the changes of ionic EC contribution percentage of K^(+)were similar,but those of other anions in potassium salts varied greatly.The relative errors of estimated EC of nutrient solutions based on ionic activities were only 1.3%in horticultural experimental nutrient solution and 1.8%in Yamasaki tomato nutrient solution with different relative concentrations compared to measured EC.The relative errors of estimated EC of nutrient solutions with specific salt added were only 0.1%-0.5%compared to measured EC in two nutrient solution.Therefore,the dynamic feedback control of ionic concentration of nutrient solution could be realized by using EC measurement combined with ionic EC contribution percentage to improve the ionic quantitative control in nutrient solution.The EC control of nutrient solution in automatic irrigation system might be upgraded to ionic concentration control by using algorisms above of ionic EC contribution percentage and EC estimation to meet dynamic demands of hydroponic crops for ionic concentration in different growth stages.