Yield,blossom-end rot incidence,and fruit quality in pepper plants under moderate salinity are affected by K and Ca fertilization

One of the most important factors limiting agricultural expansion and production is the restricted supply of good quality water. The present study examines the effects of K⁺ and Ca²⁺ fertilization on sweet pepper production, blossom-end rot (BER) incidence and fruit quality of pepper plants (Capsicum annuum L.) grown under moderate saline conditions. Pepper plants were grown in a controlled-environment greenhouse under hydroponic conditions with different nutrient solutions obtained by modifying the Hoagland solution. The experiment consisted on four K⁺ treatments (0.2, 2, 7 and 14 mM) +30 mM NaCl, and four Ca²⁺ treatments (0.2, 2, 4 and 8 mM) +30 mM NaCl, having in common a control without salt with 7 mM K⁺/4 mM Ca²⁺. Salinity decreased total fruit yield and marketable fruit yield by 23% and 37%, respectively. The marketable fruit yield reduction by salt treatment was mainly due to the increase in the number of fruit affected by BER. This typical physiopathy of the pepper fruits occurred between 18 and 25 days after anthesis (DAA), when the highest fruit growth rate was reached. Fruit quality parameters were also affected by salt treatment where the fruit pulp thickness and firmness were decreased, and fructose, glucose and myo-inositol fruit concentrations increased with salinity relative to fruits from control treatment. Under saline conditions an increased supply of K⁺ reduced the fruit fresh weight, the percentage of BER and the marketable yield although promoted the vegetative growth. However, increasing Ca²⁺ concentration in the nutrient solution increased the fruit production, and the marketable yield as consequence of decreasing the percentage of fruit affected with BER. Fruit quality parameters also were affected by the K⁺ and Ca²⁺ treatments.     

Effects of an evaporative cooling system on greenhouse climate,fruit disorders and yield in bell pepper (Capsicum annuum L.)

Summary

The main goal of this research was to investigate the effects of a wet pad-and-fan evaporative cooling system (ECS) on the incidence of blossom-end rot (BER) and fruit cracking in greenhouse-grown bell pepper (Capsicum annuum L.). The specific objectives were: (i) to study the efficiency of the wet pad-and-fan ECS in improving plant water status and reducing transpiration; and (ii) to explore the impact of these conditions on fruit yield, fruit Ca content and the incidence of BER and fruit cracking. For 3 years, peppers were grown in the Lachish Region, Israel, in a greenhouse divided into two compartments, one with and one without (control) a pad-and-fan ECS. The results showed that the ECS increased total fruit yield and the incidence of cracked fruits, but reduced the incidence of BER. The efficiency of the ECS in reducing temperature and vapour pressure deficit (VPD) decreased as the distance from the wet pad increased. Consequently, the incidence of cracked fruits decreased with distance from the wet pad, whereas the incidence of BER increased.     

The effect of nitrogen fertilization and shading on the incidence of “colour spots” in sweet pepper (Capsicum annuum) fruit

SUMMARY

“Colour spots” (CS) in pepper fruit is a physiological disorder characteristic of some sweet pepper cultivars. The symptoms are yellowish spots on the outer surface of affected fruits. We investigated the effects of shading and nitrogen supply on the susceptibility of three sweet pepper cvs (Maor, Lady Bell and 899) to CS. The most susceptible was ‘Maor’. The incidence of CS was promoted by high N and shading. The fruits of all cultivars had lower nitrogen concentrations than the leaves but there were no significant differences in fruit N content between Maor and the CS-insensitive cultivars. The CS-affected areas of the pericarp tissue had higher calcium concentrations than unaffected tissue. Differences in magnesium or potassium concentrations in these spots were less pronounced. Scanning electron microscopy revealed that the affected pericarp cells contained crystals, presumably of calcium oxalate. Only in ‘Maor’ fruits was the oxalate concentration elevated by approximately nine-fold when the nitrogen supply to shaded plants was increased. We suggest that in the fruits of the sensitive cultivar, oxalic acid production is enhanced under high-nitrogen + shading conditions and causes the CS damage, possibly be chelating intracellular calcium.     

Blossom-end rot is associated with impairment of sugar metabolism and growth of pepper (Capsicum annuum L.) fruits

Summary

Blossom-end rot (BER) in pepper fruits is known as a “physiological” disease which is evoked by climatic and osmotic stresses (e.g., high temperatures and salinity) and by deficit irrigation management. The physiological and biochemical mechanisms involved in the stimulation of BER are still a matter of dispute. It has been proposed that BER occurs under cultivation conditions that accelerate fruit growth beyond calcium supply to the growing tissue. In the present study, we investigated this hypothesis by recording fruit growth and sugar metabolism under normal and BER-inducing conditions.The results showed that pepper fruits grown in a ventilated-cooled greenhouse, which ameliorated BER, had a higher initial growth rate than those grown in a non-cooled greenhouse, but had lower calcium concentrations in the fruit pericarp. Fruits that grew without ventilation-cooling had higher concentrations of apoplastic and symplastic sucrose and reducing sugars, and higher levels of symplastic starch than those that developed in a cooled greenhouse. Concomitantly, fruits that developed in a non-cooled greenhouse had lower acid invertase, sucrose synthase and fructokinase activities than those that developed in a cooled greenhouse. Accordingly, the non-necrotic part of BER-affected fruits had higher concentrations of symplastic starch, reducing sugars and sucrose than healthy fruits. These findings indicate that the occurrence of BER in pepper fruits was associated with impaired sucrose metabolism in fruit tissues, which led to reductions in growth rate and final size. Thus, the present findings negate the notion that BER occurs when fruit growth rate is stimulated, and favour the idea that direct impairment of fruit sugar metabolism and of normal fruit growth are involved.     

Effect of two irrigation rates on yield,incidence of blossom-end rot,mineral content and free amino acid levels in tomato cultivated under drip irrigation using saline water

Summary

An experiment investigated the effects of two rates of irrigation, one of which reflected a substantial degree of water stress, on the mineral content, free amino acid levels and incidence of blossom-end rot (BER) in tomato (Lycopersicon esculentum Mill. `Durinta'). The plants were grown in the open with drip irrigation using saline water from a well (mean EC_w 5.2 dS m²¹). The yield per plant was higher and fewer fruit were affected by BER in the treatment involving the higher level of irrigation. The fruit of the first and fifth truss, and the leaves immediately above, were analysed for their macronutrient, micronutrient and free amino acid content. The macronutrient leaf and fruit content hardly showed any difference, only the N concentration in fruit being significantly affected in the water stressed plants, in which the levels were higher. The Ca concentration in the stylar portion of mature fruit, which is related with the incidence of BER, was not significantly affected by the level of irrigation. As regards micronutrients, only the Fe (in leaf and fruit of the first truss), Cu (in leaf of the first truss), Zn (in leaf and fruit of the first truss, and leaf of the fifth truss) and Mn (in leaf of the first truss) concentrations differed significantly. The total free amino acid leaf content was similar in both irrigation treatments. However, the total free amino acid content of fruit, significantly those of the first truss, was higher in the less irrigated treatment. The amino acids: aspartic acid (only from the first.truss), glutamic acid, proline and alanine had high concentrations in the fruit of the less irrigated plants, while the g-aminobutyric acid and phenylalanine (only from the fifth truss) concentrations were higher in fruit of the more irrigated plants.     

Apoplastic anti-oxidants in pepper (Capsicum annuum L.) fruit and their relationship to blossom-end rot

Summary

The aim of the present research was to study changes in the major anti-oxidative enzyme activities known to be associated with the apoplast, during the induction of blossom-end rot (BER) in bell pepper (Capsicum annuum L.) fruits grown under saline conditions. Pepper plants of the BER-sensitive cv. ‘Mazurka’ and less-sensitive cv. ‘Selica’ were grown under control, low- and high-salinity irrigation regimes. Fruits were harvested continuously and, after approx. 7 months under these conditions, BER symptoms started to appear (in the Spring season) and fruits were sampled for biochemical measurements. The intercellular washing fluid (IWF; apoplast fraction) of the fruit pericarp was prepared and enzyme activities in that fraction were determined. The results showed that production of reactive oxygen species (ROS) in the fruit apoplast was higher in ‘Mazurka’ than in ‘Selica’. Apoplastic peroxidase and superoxide dismutase (SOD) activities, and the concentration of ascorbic acid, increased during ‘Selica’ fruit development, whereas the concentration of H₂O₂ decreased. During the stage of rapid growth, when fruits are most susceptible to BER, apoplastic peroxidase activity was greatly enhanced in the healthy pericarp of BER-affected fruits compared to healthy fruits. Under saline conditions, apoplastic peroxidase and SOD activities, as well as ascorbic acid and H₂O₂ levels, increased in healthy fruits of the resistant cultivar ‘Selica’; whereas, in healthy fruit of the BER-sensitive cultivar ‘Mazurka’, apoplastic peroxidase activity decreased while the level of ascorbic acid increased, but to a much lesser extent than in ‘Selica’. SOD activity and H₂O₂ levels increased similarly in both cultivars with increasing levels of salinity. It is proposed that apoplast-associated peroxidase activity and ascorbic acid concentration are increased coordinately in response to salt stress and may be part of a protective anti-oxidation mechanism that determines cultivar sensitivity to BER.     

Effects of night-time humidity and nutrient solution concentration on the calcium content of tomato fruit

Calcium intake into tomato fruits was greater when nights were humid rather than dry and nutrient solutions dilute rather than concentrated.The concentration of calcium in the wall tissue of the distal segment of fruits damaged by blossom-end rot was 0.03% of dry matter, but was 2- to 3-fold greater in the most favourable conditions of humidity and solution concentration, when fruits were undamaged.Adding extra calcium to the nutrient solution increased the calcium concentration in the proximal, but not in the middle or distal, segments of the fruit.The results support the hypothesis that a positive root pressure at night promotes transport of calcium into tissues and organs that have restricted transpiration.     

Water relations,growth, yield,and fruit quality of hot pepper under deficit irrigation and partial rootzone drying

We compared two water-saving irrigation practices, deficit irrigation (DI) and partial rootzone drying (PRD), for their effects on growth and quality of ‘Ancho St. Luis’ hot pepper (Capsicum annum L.). The treatments were: commercial irrigation (CI) considered as the control, irrigating both sides of the rootzone with half of the volume of CI considered as DI, and alternating irrigation between two sides of the rootzone with half the volume of CI at each irrigation time considered as PRD. Midday leaf water potentials of PRD and DI plants were lower by 0.15 and 0.30 MPa, respectively, than of CI plants from 130 days after sowing. Total fresh mass of fruit was reduced by 19 and 34.7% in PRD and DI, respectively, compared to CI. Fruit number per plant was reduced by more than 20% in PRD and DI compared to CI. Total dry mass of fruit was similar among the treatments. At harvest, DI fruit had 21% higher total soluble solids concentration and better colour development than other treatments. Although incidence of blossom-end rot was high in PRD and DI fruit, more than 80% of fruit from PRD was not affected. DI and PRD saved 170 and 164 l of water, respectively, compared to CI and they could be feasible irrigation strategies for hot pepper production where the benefit from saving water outweighs the decrease in total fresh mass of fruit.     

Distribution of nutrients in the root zone affects yield,quality and blossom end rot of tomato fruits

Summary

Tomato plants (Lycopersicon esculentum Mill. `DRK') were grown hydroponically in two experiments to determine the effects of nutrient concentration and distribution in the root zone on yield, quality and blossom end rot (BER). The plants were grown in rockwool with their root systems divided into two portions. Each portion was irrigated with nutrient solutions with either the same or different electrical conductivity (EC) in the range 0 to 6.dS m^±1. In both experiments, fruit yields decreased as EC increased from moderate to high when solutions of equal concentration were applied to both portions of the root system. However, higher yields were obtained when a solution with high EC was applied to one portion of the root system and a solution of low EC to the other portion. For example, the fresh weight of mature fruits in the 6/6 treatment was only 20% that of the 3/3 treatment but the 6/0 treatment had a yield that was 40% higher. The reduction in yield in the high EC treatments was due to an increase in the number of fruits with BER and smaller fruit size. BER increased from 12% to 88% of total fruits as EC increased from 6/0 to 6/6 and fruit length decreased from 67.mm to 52.mm. Fruit quality (expressed as titratable acidity and soluble solids) increased as EC increased. In summary, high yields of high quality tomatoes with minimal incidence of BER were obtained when one portion of the root system was supplied with a solution of high EC and the other portion with a solution of moderate or zero EC.     

Effects of growth retarding treatments on apple tree growth,fruit maturation and fruit abscission

SUMMARY

Eight days after petal fall in 1991, mature 'Delicious'/MM. 106 apple trees and four days after petal fall in 1992, mature 'McintoshVMM. 106 were ringed, scored, root pruned (1 m from the trunk, two sides, 30 cm deep), or treated with ethephon (500 mg 1¹). Only ringing and scoring reduced vegetative growth. Ethephon advanced fruit maturation and fruit abscission, but root pruning did not affect the trees or fruit significantly. Mature 'Cort-land'/M.7a apple trees were root pruned 8 d after petal fall in 1991 and/or at full bloom in 1992. Root pruning reduced shoot growth, even in the year after treatment. Fruit abscission was reduced in 1991 and 1992 by root pruning in 1991, but root pruning in 1992 had no impact on abscission, in 1992. In an additional experiment, mature 'Mcintosh'/ MM.106 were root pruned 4 d after petal fall in 1991 or root pruned both in 1991 and at full bloom in 1992. Growth and preharvest fruit abscission were reduced in both the year of root pruning and the year after.     

The susceptibility of modern tomato cultivars to blossom- end rot in relation to salinity

Three cultivars, Counter, Calypso and Spectra, were grown in NFT at a range of salinities (electrical conductivities of 5,10 and 15 mS cm^-1) in two successive crops during the year. The incidence of blossom-end rot (BER) in ‘Calypso’ and ‘Spectra’ was substantially higher than in ‘Counter’ at all salinities. In the early crop, ‘Calypso’ had the highest incidence of BER at 10 mS cm^-1, of which the proportion of international BER was greater than in ‘Spectra’. In the late crop, ‘Spectra’ had a higher incidence of BER than ‘Calypso,’ and a higher proportion of external BER. In the early crop, the incidence of BER in both cultivars grown at 10 mS cm"1 was higher than those at 15 mS cm^-1, mainly due to an exceptionally high incidence of internal BER. In the late crop, however, the reverse was true. ‘Counter’, which is not susceptible to BER, had a higher shoot dry weight than the two BER susceptible cultivars. Nevertheless, ‘Calypso’ and ‘Spectra’ set more fruit in the lower and upper trusses respectively. A high incidence of BER was related to a high number of fruit set in the susceptible cultivars. Both the Ca content and the daily rate of Ca accumulation in the fruit were reduced by salinity, but no differences between cultivars were observed. The distal placenta and locular tissues had the lowest Ca content in the whole fruit and appeared to be the site of the earliest symptoms of BER. The interaction between cultivar and salinity affecting the Ca content of these tissues was not significant. The causes of susceptibility to BER in tomato are discussed.     

Effect of electrical conductivity,fruit pruning,and truss position on quality in greenhouse tomato fruit

Summary

The combined effects of electrical conductivity (an EC of 2.5 dS m^–1 or 8 dS m^–1 in the root zone) and fruit pruning (three or six fruit per truss) on tomato fruit quality were studied in a greenhouse experiment, planted in January 2005. Taste-related attributes [dry matter content (DM), total soluble solids content (SSC), titratable acidity (TA), glucose, fructose and citric acid content] and health-promoting attributes (lycopene, βcarotene, vitamin C, and total anti-oxidant activity) of tomato fruits harvested on the vine from the fifth or tenth truss positions were determined. The quality of tomato fruits was improved by high EC. A high EC in the root zone increased the DM content, total SSC, TA, as well as glucose, fructose and citric acid contents. A significantly higher lycopene and βcarotene content was also observed [on a fresh weight (FW) and dry weight (DW) basis] with a high EC in the root zone. The accumulation of different compounds that determine tomato fruit quality differed between the fifth and tenth truss. In particular, the lycopene content was reduced, whereas the βcarotene content was increased in the tenth truss with respect to the fifth truss, most likely because of higher temperatures during ripening of the tenth truss. Fruit pruning increased fruit FW by 42% and positively influenced the DM content and total anti-oxidant activity, while a negative effect was observed on lycopene and citric acid contents (on a FW and DW basis). EC and fruit pruning both had a strong effect on fruit size; however, EC had a much stronger impact on taste and health-related fruit quality attributes. A small interaction between EC and fruit pruning was found for marketable yield, fructose and glucose content, fruit firmness, and P and Ca concentrations in fruits.     

不同整枝方式对设施辣椒产量和性状的影响

辣椒是一种常见的蔬菜,整枝方式是影响温室辣椒生长性状和产量的关键因素之一。本文以尖椒品种昊瑞102为试材,通过研究整枝方式对辣椒产量、单果质量、果实长度和宽度、植株发病率的影响,探讨了更适合设施辣椒生产的整枝方式。结果表明,四秆平面整枝在果实产量、品质方面要比其他整枝方式好,尤其是在单果质量上,四秆平面整枝比对照(不整枝)的单果质量提高了75%;发病率比对照的下降了9.34%;果实厚度比对照增加了38.10%。     

Influence of slip size,deslipping and decrowning on the ‘Sugarloaf’ pineapple

Definitions: Crown = the short stem and leaves growing from the apex of the fruit. Slip = leafy branch, attached below the fruit, developed from axillary bud on the peduncle. Happa = branch arising from axillary bud at the point of junction of peduncle and stem.Large-slip plants of ‘Sugarloaf’ pineapple (Ananas comosus) (L.) Merr.) were more vigorous than small-slip plants initially; however, plants from smaller slips caught up in size within a year after planting. Large-slip and medium-slip plants produced more slips and happas than small-slip plants. Smaller slips produced heavier and larger crowns, delayed both flowering and fruit maturity, reduced fruit size and yield, and recorded a higher incidence of sunburn. Slip size did not influence sucker development, peduncle size, and % TSS, % acidity and TSS/acidity ratio of the fruit.Deslipping, and decrowning and deslipping together produced significantly more suckers than control and decrowning-treatments. Deslipping-, and decrowning and deslipping together produced the maximum fruit weight and yield, whilst deslipping produced the longest fruits. Sunburn was greatest on decrowned and deslipped fruits, followed by deslipped fruits and then by control and decrowned fruits. Pruning did not influence happa production, peduncle size, fruit maturity, and % TSS, % acidity and TSS/acidity ratio of the fruit.No significant interaction between slip size and pruning was found.     

Sensitive stages of fruit and seed development of chili pepper (Capsicum annuum L. var. Shishito) exposed to high-temperature stress

The sensitivity of developmental stages to high temperature was investigated in chili pepper (Capsicum annuum L. var. Shishito). Plants were subjected to heat stress (38/30 °C day/night) immediately after anthesis for 5 or 10 days, or from 10 to 30 days after anthesis (DAA), from 30 DAA until harvest of the seeds, or immediately after anthesis until harvest of the seeds. Control plants were grown at 30/22 °C (day/night). Exposure to high temperature (heat stress) during different periods of development after anthesis adversely affected fruit growth, seed yield, and seed quality in chili pepper. Heat stress for the whole period after anthesis, and from 30 DAA until harvest reduced the growth period of chili fruits by 15 and 10 days, respectively. Heat stress from 10 to 30 DAA reduced fruit width and fruit weight. The early stage of seed development from anthesis until 10 DAA was sensitive to high temperature, which affected fruit length, fruit weight and seed set. Applying high temperatures to plants for 10 DAA increased the proportion of abnormal seeds per fruit. High temperatures from 10 DAA until 30 DAA inhibited carbohydrate accumulation and adversely affected seed germinability and vigor. These results suggest that the stage of development at which chili peppers are exposed to high temperatures is an important factor in fruit and seed growth and in seed quality.     

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.     

Influence of fruit load on dry matter and N-distribution in sweet pepper plants

The influence of fruit load on the leaf characteristics and on the distribution of dry matter (DM) and nitrogen (N) in sweet pepper (Capsicum annuum L., cv. Cornado) plants was investigated under Mediterranean glasshouse conditions during a winter–spring production cycle (from December till June). DM weight of all organs (roots, stems + petioles, leaves and fruits) and N content were determined throughout the growing cycle over a 3-week interval. The results showed that the cyclic fruit load pattern (production flushes) was associated with strong variations of N-leaf content on an area basis and specific leaf weight, SLW. On a whole plant scale, the value of SLW dramatically decreased (≈30%) with increasing fruit load; the reverse held true as long as the fruit dry weight remained low (<30 g pl⁻¹). The decline in SLW was coincident with a shift in distribution of DM and N in the plant, both preferentially diverted to the fruits. The time evolution of DM and N fractions in organs exhibited periodic fluctuations, with a duration close to the length of a fruit growth cycle (about 70 days, from anthesis to harvest). Linear relationships were found between the fraction of dry mass and N in fruits, and those of the other organs. The slope of these relationships was considered as an indicator of the response and sensitivity of the organ growth to an increase in fruit load. The root dry mass fraction was the most affected by increases in fruit load (slope of −0.75), while the N fraction in roots and in leaves was affected to a similar extent (slope of −0.50 and of −0.40, respectively). We conclude that, in the sweet pepper, the cyclic pattern of fruit load induces opposite cyclic patterns of dry matter and N content in the other aerial organs as well as in the roots, thereby reflecting close shoot–root coordination in the allocation of carbon and nitrogen resources among the organs. Finally, we discuss the possible implications that could derive from these findings for modelling dry matter partitioning in plants subjected to continuous fruit harvesting.     

Effect of NaCl on growth,ion composition and ascorbic acid concentrations of capsicum fruit

Potted plants of Capsicum annuum, cultivar ‘Long Sweet Yellow’, were restricted to two fruits each and supplied with 0, 10, 25 and 50 mM NaCl. Chloride concentrations exceeded sodium concentrations in ripe fruit from all salt-treatments. The difference was 2.5-fold in ripe fruit from plants treated with 50 mM NaCl. Fruits from the 50 mM treatment were markedly lower in fresh weight and were of a more intense colour than control fruit. Fruit ripening was accelerated by all salt-treatments, but the fresh weight to dry weight ratio of ripe fruit was reduced; the reduction was in proportion to the stress applied.A significant correlation was found between fruit ascorbic acid and Ca^{2 +} concentrations. Fruit Ca^{2 +} was reduced by salinity, but the reduction was not in proportion to sodium chloride concentration. Additional calcium nitrate in the nutrient solution increased the Ca^{2 +} content and ascorbic acid concentration in fruit on control plants but not in fruit from plants treated with 50 mM NaCl. Instead, these fruit showed a marked increase in Na⁺.     

Effects of tree age at planting,root manipulation and trickle irrigation on growth and cropping of apple (Malus pumila) cultivar Queen Cox on M.9 rootstock

Summary

The apple cultivar Queen Cox on M.9 rootstock cropped more precociously when planted as two year old trees than when planted as one year old trees, even though there were no significant differences in the sizes (leader height and branch length) of the trees at the time of planting. However, the two year old trees had larger root systems at planting. As the trees aged, those planted as one year olds grew more vigorously and bore higher cumulative yields than those planted as two year olds. Annual root pruning of the trees, commencing 15 months after planting, reduced extension shoot growth, crown volume and grubbing weights (final fresh weights of scions) severely. In some seasons root pruning increased the number of spur and terminal floral buds produced and also the final sets and yield efficiencies on the treated trees. Planting trees within semi-permeable fabric membranes also reduced extension shoot growth and tree size, but less severely than the root-pruning treatment. Root restriction increased the efficiency of fruit set and yields and also improved the grades of fruits produced. Trickle irrigation treatments increased shoot growth and tree fresh weight at the time of grubbing, but had inconsistent and small effects on fruit set and yields. Interactions between tree age at the time of planting and the root manipulative treatments were significant.     

钙素营养与套袋苹果苦痘病的关系

为了探讨苹果套袋后苦痘病加重的原因,以富士苹果为试材,对果实发育过程中钙、氮含量的变化规律,果实幼果期和成熟期钙总量,套袋后果实微环境湿度变化及不同有机质果园苦痘病发生率进行了测定。结果表明,未套袋苹果果实在幼果期吸收钙量占成熟果实总钙量30%左右,后期占70%左右,套袋影响了果实对钙的吸收;套袋使袋内湿度增加,果实表面蒸腾作用降低,使果实对钙的吸收受到影响;同时套袋果氮含量一直高于未套袋果,N/Ca增大,促成了苦痘病的发生。增加果园有机质含量,可以改善根际钙离子供应,降低苦痘病的发生。