Photosynthetic and growth responses of juvenile Chinese kale (Brassica oleracea var. alboglabra) and Caisin (Brassica rapa subsp. parachinensis) to waterlogging and water deficit

Chinese kale (Brassica oleracea var. alboglabra) and Caisin (Brassica rapa subsp. parachinensis) are leafy vegetable crops grown in south-east Asian countries where rainfall varies dramatically from excess to deficit within and between seasons. We investigated the physiological and growth responses of these plants to waterlogging and water deficit in a controlled experiment in a glasshouse. Juvenile plants were subjected to waterlogging or water deficit for 19 days in case of Chinese kale and 14 days in case of Caisin and compared with well-watered controls. Caisin tolerated waterlogging better than Chinese kale because it produced hypocotyl roots and gas spaces developed at the stem base. In Chinese kale, waterlogging reduced plant fresh weight (90%), leaf area (86%), dry weight (80%) and leaf number (38%). In contrast, waterlogging had no impact on leaf number in Caisin and reduced plant fresh and dry weights and leaf area by 60–70%. Water deficit reduced leaf area, fresh weight and dry weight of both species by more than half. Leaf number in Chinese kale was reduced by 38% but no effect occurred in Caisin. Water deficit increased the concentration of nitrogen in the leaf dry matter by more than 60% in both species and the leaf colour of water deficient plants was dark green compared with the leaf colour of well-watered plants. Soil water deficit delayed flowering of Caisin while waterlogging accelerated it. Thickening and whitening of the cuticle on the leaves of Chinese kale probably increased its ability to retain water under drought while Caisin adjusted osmotically and Chinese kale did not. Waterlogging and water deficit had strong effects on leaf gas exchange of both Brassica species. Water deficit closed the stomata in both species and this was associated with a leaf water content of 9 g g⁻¹ DW. In contrast, waterlogging reduced conductance from 1.0 to 0.1 mol H₂O m⁻² s⁻¹ in direct proportion to changes in leaf water content, which fell from 11 to 5 g g⁻¹ DW. This separation of the effects of water deficit and waterlogging on conductance was reflected in transpiration, internal CO₂ concentration and net photosynthesis. In conclusion, Chinese kale and Caisin showed rather different adaptations in response to waterlogging and water deficit. Caisin was more tolerant of waterlogging than Chinese kale and also showed evidence of tolerance of drought. There is genetic variation to waterlogging within the Brassica genus among the leafy vegetables that could be used for cultivar improvement.     

Effects of multiple applications of methyl jasmonate on fruit ripening,leaf gas exchange and vegetative growth in fruit trees

Summary

Multiple applications of methyl jasmonate (Me-J), at 10.mM, enhanced the rate of fruit ripening in peach ‘Redhaven’. The effect of Me-J on red colour development and fruit firmness was most pronounced in fruit treated six times with Me-J. Lower concentrations of Me-J had no effect of fruit colour. Me-J, at 10.mM, significantly reduced stomatal conductance, photosynthetic rate and transpiration rate of crabapple leaves, but had no effect on these parameters in peach leaves. The short-term inhibitory effects of Me-J on leaf gas exchange in crabapple persisted for up to 24 h. Fourteen applications of Me-J over a period of 28 days resulted in a 60% decrease in the concentration of chlorophyll in leaves. These Me-J applications also reduced the length of new branches, leaf number and leaf fresh weight by 65%, 31% and 47%, respectively. In peach, Me-J induced some leaf chlorosis and early leaf senescence within two weeks of the treatments which resulted in significant reductions in shoot length.     

Competition for water between inflorescences and leaves in cut flowering stems of Grevillea ‘Crimson Yul-lo’

Summary

Grevillea cv. ‘Crimson Yul-lo’ has large bright red terminal inflorescences on leafy stems and has recognised commercial potential as a cut flower crop. A major limitation is its relatively short vase-life, often terminated by early wilting of the inflorescence despite apparently turgid leaves. An investigation of the water relations of cut Grevillea ‘Crimson Yul-lo’ stems revealed that the water potential of inflorescences on intact stems in vases was significantly higher (i.e., less negative) than that of leaves from day-0 to day-3 of vase-life. Thereafter, the water potential of inflorescences declined more rapidly than that of leaves, accompanied by visible wilting of the tepals and styles of individual florets. Removal of leaves from the stems reduced both water uptake and water loss, and delayed the onset of a negative water balance in the inflorescence. Bagging of entire stems, leaves only, or inflorescences only, with micro-perforated plastic film to reduce transpiration, reducing leaf number to reduce leaf area, or supplying abscisic acid to reduce leaf stomatal aperture, all aided relative fresh weight retention by stems and extended vase-life. Four or six leaves on a stem caused greater loss in inflorescence water content than zero or two leaves. Considered collectively, these findings show that competition for water between the inflorescence and the leaves in cut Grevillea ‘Crimson Yul-lo’ stems contributes to the onset of inflorescence wilting and their short vase-life.     

Nickel supplementation effect on the growth,urease activity and urea and nitrate concentrations in lettuce supplied with different nitrogen sources

Effect of nickel (Ni) in the nutrient solution on yield, N metabolism, and nitrate content of leafy vegetables is poorly understood. The aim of this nutrient solution culture experiment was to investigate the effects of Ni supplementation on the nitrogen (N) metabolism and growth of lettuce (Lactuca sativa L. cv. Baker) with either urea or nitrate as the N source. Nickel supplement at 0.04 μM reduced urea toxicity to the urea-fed plants. Addition of Ni to the nutrient solution significantly increased the leaves and root growth of the urea-fed lettuce plants while it increased the growth of lettuce plants fed with nitrate only at N level of 20 mM. At N level of 20 mM, the leaves fresh weight of the urea-fed plants promoted by Ni supplement was comparable with the nitrate-fed plants untreated with Ni. Nickel supplementation increased the leaf total N concentrations in the urea-fed plants, although the nitrate-fed plants accumulated greater N in their leaves compared with urea treated plants at without Ni treatment. Nickel addition decreased the concentrations of leaf urea-N in the urea-fed plants and NO₃-N in the nitrate-fed plants. Nickel addition enhanced urease activity in the leaves of urea-fed plants. The results indicated Ni supplementation enhances the growth of the urea-fed lettuce plants while it has role in decreasing leaf nitrate concentration and thus, improving the health quality of the nitrate-fed plants.     

Yield and quality of Corchorus olitorius baby leaf grown in a floating system

Corchorus olitorius is mainly cultivated in Africa and is used in the human diet for its nutraceutical proprieties. In this work, C. olitorius was grown in a floating system using a standard (NS100%) or halved (NS50%) nutrient solution. Yield was evaluated at harvest when plants reached the baby leaf stage. Quality of leaves was estimated by measuring sugars, nitrate, chlorophylls, carotenoids, polyphenols, and anthocyanins. Yield was similar to other common leafy vegetables cultivated in floating systems. Analytical determinations showed good levels of antioxidant compounds and sugars. Mineral contents were relevant for Ca, Mg and Fe in comparison with C. olitorius cultivated in soil and other common leafy vegetables. Results showed these plants had healthy characteristics for human nutrition, in particular for women and children. C. olitorius had a good performance in the floating system with yield ranging from 0.8 to 2.4 kg m^?2. Mineral nutrient levels were higher than in the major leafy vegetables. Nutrient solutions influenced anthocyanin accumulation (+37% in NS50% in spring and +48% in NS50% in summer). Leaf nitrate content was –50% in NS50% at spring cultivation. The overall quality parameters suggest that C. olitorius can be an optimal candidate for baby leaf production in the fresh cut leafy vegetable industry.     

Effects of suboptimal low temperatures on plant architecture and flowering in muskmelons Cucumis melo L.

Summary

The effects of suboptimal cold temperatures were investigated in an array of vegetative, reproductive and leaf characters in 34 cultivars, both open pollinated and hybrid, of melons, Cucumis melo. The cultivars were grown in two treatments: (i) a heated greenhouse (T1) that produced temperatures similar to those used in commercial cultivation in winter; and (ii) an unheated greenhouse (T2) that produced significantly lower night-time temperatures than T1. Plants grown in T1 had significantly longer main stems and internode lengths, more nodes and more potassium in their leaves but less leaf biomass than plants grown in T2. Plants from T2 also had more green and yellow leaf colour than plants from T1. Open pollinated cultivars had significantly longer main stems, more nodes and more green and yellow leaf colour than hybrid cultivars. Significant differences were found among the cultivars in all traits.     

都市绿叶蔬菜价格波动原因与对策研究

以上海为例,通过对大城市郊区绿叶蔬菜的生产现状、生长发育规律、气候、市场价格和政策导向等造成绿叶蔬菜的价格波动的原因进行分析,借鉴国内外绿叶蔬菜生产的相关经验,提出了确保生产能力、合理区位布局、加强生产技术保障、促进产销衔接和完善扶持政策等对策措施。     

The fractal spectrum of leaf colour as a tool for measuring frost hardiness in plants

Summary

An image analysis method, based on the calculation of the fractal spectrum of leaf colour, was evaluated for its potential use in assessing frost hardiness in plants. The technique developed consisted of a) digitization of the leaves after freezing treatments, b) splitting of the images obtained into the three components of the RGB (red, green and blue) colour system and c) calculation of the fractal spectrum for each colour component of the leaf. It was then tested to assess the freezing hardiness of acclimated and non-acclimated Callistemon linearis plants. The analysis system consisted of a scanning device, a personal computer and the image analysis algorithm. All the fractal parameters showed a sigmoidal relationship with temperature. From the inflection point, the LT₅₀ calculated for acclimated and non-acclimated plants, was –7.5 and –4.8°C, respectively. The LT₅₀ calculated from the electrolyte leakage test on the same material was about 2°C warmer than the LT₅₀ obtained from fractal analysis. The role of fractal analysis of leaf colour as an additional, rapid and inexpensive method for identifying freezing damage is discussed.     

Effect of CPPU on fruit and shoot growth of apple

The effects of CPPU on the growth of fruits and bourse shoots of apple were examined by targeted applications of 20 mg I“1 CPPU to fruitlets and/or bourse-shoot and spur leaves. Treating fruitlets and fruitlets-plus-leaves stimulated fruit growth to a similar extent; fruit growth rate was temporarily suppressed when only the leaves were treated. Conversely, bourse shoot growth was stimulated by leaf and leaf-plus-fruit treatments. All CPPU applications reduced the content of fruit soluble solids and induced a paler yellowish- green fruit ground colour.     

不同光照强度对叶菜类观赏蔬菜生长的影响

以4种观赏叶菜类蔬菜为试材,以10%、30%光照为不同处理,研究了不同光照强度对其生长的影响。结果表明:随着光照强度的减弱,材料的叶色变浅、株形松散;株高、叶数、净光合速率、叶绿素含量及干鲜重等也随光照强度的下降有不同程度的下降。     

家庭阳台蔬菜种植方式的初步探索

以适合阳台栽植的菜心、白菜和芥菜3种叶菜的9个品种为材料,在施肥处理上采用常规管理与水肥一体化两种模式,初步探索了阳台蔬菜在两种栽培模式下的生长和发育状况。试验结果表明,在相同施肥管理栽培模式下,不仅菜心、白菜与芥菜3种蔬菜间的产量存在差异,且相同蔬菜的不同品种的地上部鲜质量也存在差异,但是菜心、白菜和芥菜均一致表现出在水肥一体化栽培模式下的植株地上部鲜质量高于常规管理模式,增幅分别为13.83%~51.60%、34.26%~35.24%、16.36%~26.70%,植株收获期根冠比则均低于常规管理模式。     

Response to water stress of some oleander cultivars suitable for pot plant production

Oleander (Nerium oleander L.) is an evergreen shrub of great ornamental interest which, in recent times, has been increasingly used as a flowering pot plant. Plants grown in pots undergo more frequent water stress conditions than those grown in the soil, due to the limited volume of substrate available for the roots. Oleander is a species adaptable to dry conditions and able to survive long periods of drought. It is well known that under water stress conditions all plants reduce photosynthetic activity, resulting in reduced plant growth. In case of severe water stress, leaves undergo strong wilting and senescence resulting in the loss of ornamental value. In the present work, a study was conducted to evaluate the ecophysiological response to water stress in four oleander cultivars previously recognised (on the basis of traits such as size, habit, earliness, abundance and duration of flowering, aptitude for cutting propagation and rapidity of growth) as suitable for pot plant production. Our data confirm the high drought tolerance of oleander. In the studied cultivars, plants submitted to water stress showed only minor variations in leaf gas exchange parameters [transpiration (E), stomatal conductance (g_s) and CO₂ net assimilation (A)] for at least 10 days without a change in leaf water content [assessed as relative water content (RWC)] for 22 days from the beginning of the stress treatment. During this period, non-irrigated plants maintained the same water status as control plants and were visually undistinguishable from them. Moreover, plants survived without water supply for one month. Following the supply of water again, they were able to restore RWC, gas exchange parameters and instantaneous water use efficiency [A/E ratio (WUE_inst)] to the values of control plants. Furthermore, if at the end of the stress period plants appeared withered and were pale green in colour, they regained their normal appearance after they were irrigated again. Although the four studied cultivars showed some minor differences in leaf gas exchange parameters and in the manner in which the latter parameters changed after irrigation was stopped, the response to water stress was essentially the same. Therefore, as far as drought tolerance is concerned, all these cultivars have a good aptitude for use as flowering pot plants.     

绿叶蔬菜工厂化生产关键技术研究

围绕绿叶蔬菜的清洁高效生产和均衡供应需求,借鉴日本、荷兰等国家植物工厂发展的先进经验,针对绿叶蔬菜工厂化生产的关键环节和技术突破点,以小白菜的工厂化生产为例,综述了品种选择、基质研发、肥水运筹、节能生产、绿色防控、物流加工、质量管理等关键设备与技术研究进展,探索符合中国国情的有机生态型绿叶蔬菜工厂化生产的可行性。     

红光和蓝光对葡萄叶片衰老与活性氧代谢的影响

为了明确红光和蓝光对葡萄叶片衰老与活性氧代谢的影响,以设施延迟栽培条件下叶片衰老速度不同的两个葡萄品种‘意大利’和‘无核白鸡心’为试材,分别进行补充红光和蓝光处理,以未补光处理作对照,研究其对功能叶片衰老期间叶绿素和可溶性蛋白质含量,净光合速率,丙二醛（MDA）含量,过氧化氢酶（CAT）、过氧化物酶（POD）、超氧化物歧化酶（SOD）活性及超氧阴离子自由基（）和过氧化氢（H2O2）含量的影响。研究结果表明：与对照相比,红光明显减缓了叶片中叶绿素和可溶性蛋白质含量以及净光合速率的下降,提高了CAT和SOD活性,减慢了MDA、、H2O2的上升速率,推迟了H2O2出现最大含量的时间,延缓了叶片衰老;蓝光处理下,叶片衰老前期的叶绿素含量、净光合速率、抗氧化酶活性均低于对照,加速了叶片的衰老进程,但在后期叶绿素含量、净光合速率和抗氧化酶活性逐渐高于对照,在一定程度上延缓了叶片衰老。两个品种间比较,‘意大利’叶片衰老缓慢,在生育后期仍能维持较高的抗氧化酶活性。     

Leaf pruning intensities at flowering of banana (Musa AAA,cv. Grande Naine) did not influence fruit green and yellow life and quality

This study examined the effects of leaf pruning intensities at flowering on the green and yellow life and fruit quality of bananas (Musa AAA, cv. Grande Naine). The fruit from banana plants that retained 7, 9, 11 and 13 leaves after pruning were packed in carton boxes of 13.7 kg and stored in a cold room at 14 °C for 21 days to simulate transportation conditions. During this period, eight visual evaluations of fruit peel colour were made. Next, fruits were induced to commercial ripening using ethylene at 100 μl/ml. Four evaluations (every 2 days) on fruit firmness, soluble solids, titratable acidity, fruit weight and peel colour were made to assess fruit yellow life. No interaction between evaluations and number of leaves retained was found for pulp firmness, soluble solid percentage, fruit acidity, fruit weight and maturation grade. The fruit green life and peel colour was similar for plants retaining different number of leaves. After the application of ethylene, there were no differences in fruit firmness (P > 0.62), percentage of soluble solids (P > 0.24) nor in the percentage of acidity (P > 0.32). No difference in fruit weight (P > 0.07) and ripening grade (P > 0.17) were observed among plants retaining different number of leaves. The results suggest that in tropical commercial banana plantations, producing for international markets, it is possible to defoliate the banana plants to seven leaves at flowering without causing a reduction on the green and yellow life and quality of fruit.     

Effects of controlled atmosphere,edible coating,and 1-methylcyclopropene on improving storage quality of ‘Bartlett’ pears after long-term storage

Recent trends towards greater fresh market use of ‘Bartlett’ pears has increased the need to extend its storage life to prolong the packing and marketing season in the United States Pacific Northwest region. Sixteen and 38%, respectively, of control fruit developed senescence disorders following 5 and 6 months of storage at ?1.1°C. Commercial standard controlled atmosphere (CA) conditions (O₂ at 1.5 kPa and CO₂ < 1 kPa) or edible coating (Semperfresh?, SF) prevent the appearance of senescence disorders for 5 months, but 9% and 16% of fruit, respectively, developed senescence disorders after 6 months. The combination of CA+SF completely inhibited senescence disorders for 6 months. Treatment with CA and SF, alone or in combination, maintained high-storage quality and developed ripening capacity with characteristic melting texture during storage. Senescence disorders were inhibited for 6 months by 0.3 µL l^?1 1-methylcyclopropene (1-MCP), alone or combination with CA or CA+SF. In part these pears developed ripening capacity after 6 months of storage. The combination of CA+SF+1-MCP maintained the highest storage quality with dark green colour and hard firmness, which might be associated and proportional with reductions in ethylene synthesis and respiration rate after long-term storage.     

Dormant and Summer Pruning Compared by Pruning Young Apple Trees Once on a Succession of Dates

Rooted cuttings of Malus sylvestris (L.) Mill. var. M.VII were permitted to grow from a single shoot. This was cut back to 3 cm. and the utilization of the subsequent increment, as leaves, stem and root, was determined. Different batches were treated on 7 occasions–June, July, August and December of the 1st year of the bud’s growth and March, April and June of the 2nd year. Also two further batches were cut back in the 2nd year (June and July) to the base of the 2nd year’s shoots. The growth to the end of the 1st and 2nd years was compared with that of unpruned controls.

In most cases pruning reduced the subsequent increment. Following dormant pruning (December, March, April) this reduction was associated with fewer growing shoots, although the leading shoots might be longer than comparable shoots on the controls. The reduction in increment after pruning leafy shoots was attributed to the loss of leaf and to shortening the effective growing season. Such leafy pruning was equivalent to the loss of ½ to ? of the growing season.

The relative distribution of increment (i.e. increment of the part as a fraction of the total increment) to leaf, stem and root was little affected by pruning. The main effect of pruning occurred within the stem region, where the fraction utilized by the old stem decreased, and by the new stem correspondingly increased, so that the total stem fraction changed very little. A small effect following pruning leafy shoots was that the leaf fraction increased slightly and the new stem decreased.

It is concluded that the different effects of dormant and summer pruning may be attributed to the relative importance at different times of the year of bud inhibition and curtailment of the growing season.     

Interaction of ethylene concentration and storage temperature on postharvest life of the green vegetables pak choi,broccoli, mint,and green bean

Reducing ethylene levels around produce delays the senescence of fruit and vegetables and therefore has the potential to reduce the need for refrigeration during transport and storage, which would result in substantial energy savings. In this study four non-climacteric green vegetables were stored at 0, 5, 10, and 20°C in an atmosphere containing 0.001, 0.01, 0.1, and 1.0 μL L^?1 ethylene. The results showed that the postharvest life, as determined by consumer acceptance criteria of yellowing for pak choi and broccoli, leaf abscission for mint, and pod softening and chilling injury for green bean, increased as the temperature and ethylene concentration decreased. Regression equations generated from the storage data allowed for the calculation of the temperature and ethylene levels required for any nominated postharvest life. Using a 14-day postharvest life as an example, storage in ethylene at 0.001 μL L^?1 would allow a storage temperature of about 10°C for pak choi, broccoli, and mint and about 18°C for green bean, temperatures well above the current recommendations of 0 to 5°C.     

Causes and control of calcium deficiency disorders in vegetables: a review

Summary

The aim of this study was to provide an overview of the causes and control of calcium (Ca)-deficiency disorders in vegetables. Ca-deficiency is usually related to the inability of the plant to translocate adequate Ca to the affected part. Many vegetables develop unique symptoms: for example blackheart in celery, tipburn in lettuce, chervil, onion, fennel, chinese cabbage and other cabbages, blossom end rot (BER) in tomato. Ca-deficiency disorders in vegetables can be controlled by various means. The growing medium influences the development of Ca-deficiency symptoms in plants. Restriction of the root volume is one factor that favours the development of Ca-deficiency symptoms in leafy vegetables, but reduces the incidence of BER in pepper. Ca-deficiency can also be avoided by using reasonable levels of nitrogen in the nutrient solution. Cations depress Ca-uptake and distribution, while anions depress the development of tipburn in plants. Ca-deficiency can be avoided by using the recommended level of salinity for each crop. Too high a salinity level increases the symptoms of Ca-deficiency in plants. Watering helps to prevent Ca-deficiency injury, as when growing vegetables outdoors. Maintaining an optimum soil moisture level helps to promote adequate movement of Ca to the roots and into the plant. A low relative humidity during the day-time increases the Ca-contents of leaves in leafy vegetables with an open growing point, but reduces the Ca contents of fruit and the inner leaves of leafy vegetables with a closed growing point. Avoiding too long a duration of supplementary lighting, too high a light intensity, and the use of high-pressure sodium lamps can prevent Ca-deficiency injury in plants. Shading may influence the incidence of BER, by reducing the appearance of symptoms of BER. Growing plants under a far-red wavelength filter helps to prevent Ca-deficiency disorders. Avoiding high or low temperatures also prevents Ca-deficiency injury. A negative DIF value (DIF = the difference between the day-time and night-time temperatures; a negative DIF means the night temperature is higher than the day temperature) may influence the incidence of tipburn injury by reducing its appearance. Air flow to the affected parts of plants can help to avoid the symptoms of Ca-deficiency. Ca sprays also help to prevent Ca-deficiency disorders in plants. Mulches can be used to protect plants against Ca-deficiency. Some crop varieties are less susceptible to Ca-deficiency. The plant growth regulator, Cultar (paclobutrazol, an inhibitor of gibberellin-biosynthesis), may influence the symptoms of Ca-deficiency in plants by reducing the appearance of the disorders. Planting a little later than the optimum date can avoid Ca-deficiency symptoms in leafy vegetables in Nordic countries. Harvesting a little earlier than the optimum date can also avoid Ca deficiency- symptoms in leafy vegetables.     

Postharvest quality response of strawberries with aloe vera coating during refrigerated storage

Strawberries (Fragaria × ananassa Duch.) were coated either with chitosan (1, 1.5, and 2% solution, w/v) or aloe vera (AV) gel and the coatings were air dried. Coated strawberries were put in a polypropylene box and stored in refrigerator (6 ± 1°C and 50 ± 5% relative humidity. The success of coating in retaining the postharvest quality of the strawberries was evaluated by determining respiration rate, firmness, weight loss, external colour change, ascorbic acid content, total soluble solids, acidity, pH, microbial decay and sensory quality. The incidence of microbial rot started on day-6 in uncoated and 1% chitosan coated strawberries. Strawberries coated with 1.5 and 2% chitosan were affected by microbial decay on day-9 of storage. On the other hand, rot incidence was initiated in AV gel coated strawberries on day-15 of storage. Aloe vera gel or chitosan coating reduced respiration rate, weight loss, and microbial decay and preserved firmness, ascorbic acid content, and other quality parameters, thus delaying ripening and the progress of fruit decay due to senescence or microbial attack. Furthermore, AV gel delayed the changes in external colour and retained all other postharvest quality of strawberries compared to chitosan coated or uncoated ones throughout the storage.