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.     

Effects of fruit characteristics and climatic conditions on tomato transpiration in a greenhouse

Summary

Experimental data of the transpiration and surface temperature of detached tomato fruits were collected to study and analyse how tomato fruit transpiration (E) was related to fruit characteristics, growth stage and climatic conditions. The measurements were carried out (i) in controlled conditions on fruits weighing between 10 and 140 g and (ii) during several summer days on fruits of 60–100 g under two greenhouse compartments with contrasted (high and low) levels of air vapour pressure difference (VPD_a). The transpiration rate, when expressed on a fruit area basis (g cm^–2 h–1 ), showed only a very slight dependence upon weight. Linear models relating E in unit area to (i) VPA_a and (ii) VPD (fr-a) (fruit-to-air vapour pressure difference) by means of a total conductance to water vapour (g_t), were proposed and their parameters were identified for fruits grown under the high and low VPD regimes. These models were able to explain a significant part of the observed variation in fruit transpiration. The parameters of the model differed with respect to growth conditions. The results evidenced the role of both fruit characteristics and climatic conditions on fruit transpiration and that the response of fruit transpiration to VPD could be separated into two components: (i) a short-term and reversible response which seems to be related to instantaneous changes in cuticular hydration linked to the prevailing VPD conditions and (ii) a long-term and irreversible response due to cuticle characteristics which depend on the average level of VPD experienced by the fruit during its growth.     

Cuticular cracking in pepper fruit. I. Effects of night temperature and humidity

Summary

The objective of the present study was to characterize some of the anatomical and physiological characteristics of fruit cracking in bell pepper (Capsicum annuum L.). Scanning-electron micrographs show that initiation of fruit cracking in bell pepper is by formation of mini-cracks on the cuticle layer; these then enlarge into cracks and traverse the epidermal cells. Pepper cultivars differ in their sensitivity to cracking, partly because of differences in fruit pericarp thickness. Limitation of night transpiration by high humidity or low temperature increased the turgor potential of the fruit pericarp and enhanced cracking. Likewise, leaf pruning suppressed night transpiration and concomitantly increased cracking. Fruit cuticle transpiration was found to be low in the early stages of fruit development and to increase as the fruit became susceptible to cracking. Environmental conditions which enhanced cracking also increased cuticle transpiration in a sensitive pepper cultivar but not in a less sensitive one. We suggest that fruit cracking in bell pepper occurs because reduction in night transpiration causes high turgor pressure in the fruit. As the cuticle becomes permeable to water, the inner turgor pressure causes the cuticle to crack. Differences in cultivar sensitivity may be partly due to differences in pericarp thickness and cuticle properties, but additional factors may be involved.     

果实膨大生长和吸水与气候变化之间的关系

田间和遮雨生长棚下，甜橙和荔枝果实在台风雨期间出现突发性猛长现象，而受胁迫果实的反响更加强烈。发现在果实猛长同时，果实的呼吸强度也上升。这些现象与大气的水蒸汽压亏的明显下跌有关。乙烯利溶液浸果试验证明，果实吸水的增多与乙烯利促进呼吸作用有关。果实的膨大生长主要依赖于水分的进入，果实的吸水包括被动和主动两种方式，呼吸为后乾提供能量，果实的吸水也与其本身的生长潜势有关。     

Transpiration characteristics of banana leaves (cultivar ‘Williams’) in response to progressive depletion of available soil moisture

Young parent-crop banana plants (cultivar ‘Williams’) were subjected to two soil moisture potential (SMP) regimes, namely, continuous field capacity and progressive depletion of total available soil moisture (TAM). Experiments were conducted in a fibreglass tunnel under mild or enhanced conditions of vapour pressure deficit (VPD), and also in the field during summer. Transpiration rates, stomatal resistance, photosynthetically-active radiation and leaf temperature were measured simultaneously with a steady-state porometer, according to a developed technique which minimised natural sources of error.

Under mild conditions of VPD (± 5 hPa) plants responded slowly to soil drying, and at a SMP of −82 kPa, transpiration was reduced by 27% compared to fully-irrigated plants. Under enhanced VPD (15–20 hPa), plants responded rapidly to soil drying, and at a SMP of −75 kPa transpiration was reduced by 73%.

In the field, reduction of transpiration in response to SMP at high VPD followed a similar pattern to the covered experiment. At a SMP of −46 kPa the reduction in transpiration rate was 41% in the late afternoon at high VPD, but the following morning transpiration rates of the two treatments were similar due to lower VPD and overnight re-establishment of turgor. At −525 kPa SMP, reduction of transpiration was 70% and plants could not regain turgor overnight. Stomatal conductance seemed more sensitive to water stress than transpiration, but leaf temperature only differentiated advanced levels of stress (± 2°C difference between stressed and non-stressed leaves).

These results hold important implications for irrigation scheduling of bananas. Initiation of stress occurred at a SMP of around −20 to −25 kPa which occurred at a 20% depletion of TAM, thus necessitating a summer irrigation frequency of daily or every 2 days.     

Water transport in relation to expansion and contraction of leaves and fruits of Calamondin orangef

Diurnal fluctuations in fruit diameter and leaf thickness of Calamondin orange trees were measured and related to transpiration from leaves and to internal redistribution of water from fruits to leaves. While trees were well irrigated, leaf thickness began to decline daily around sunrise and to increase in mid-afternoon. Daily shrinkage and expansion of fruits began later than in leaves. The lag in response of leaf thickness changes to changes in vapour pressure deficit of the air was 1 or 2 hours, whereas the lag in response of fruit diameter was 3 or 4 hours. During imposed droughts, daily shrinkage of fruit and leaves continued until later in the day when the trees were well irrigated. Moreover, during a drought, expansion of the tissues at night occurred at a much slower rate than during periods of daily irrigation, or expansion did not occur at all. Movement of water from fruits to leaves on excised branches was indicated by the higher percentage moisture content of leaves on branches bearing fruits than of leaves on branches without fruits.     

Evaluation and modelling of greenhouse cucumber-crop transpiration under high and low radiation conditions

The main objective of this study was to analyse the transpiration time course of soilless culture cucumber plants (Cucumis sativus L.) during two cycles, at low (up to 9 MJ m⁻² d⁻¹) and high (up to 20 MJ m⁻² d⁻¹) radiation levels, and their relationship with greenhouse climate parameters (incident radiation and vapour pressure deficit, VPD) and canopy development. The coefficients of the simplified Penman–Monteith formula were calibrated in order to calculate the transpiration rate of the crop, to help improve irrigation management in substrate cultivation. The transpiration rate per ground surface area was measured by weighing plants with an electronic balance.At high radiation levels, the diurnal canopy transpiration rate was four times higher than at low radiation levels and the night transpiration rate reached values between 120 and 200 g m⁻² d⁻¹ in both cases. The leaf transpiration rate decreased during crop ontogeny and was higher in the afternoon than in the morning for the same value of radiation, whereas a linear relationship with the VPD was found even for values greater than 3 kPa. The results showed that the fitted simplified Penman–Monteith formula accounted for more than 90% of the measured hourly canopy transpiration rate, signifying that this formula could be used to predict water requirements of crops under Mediterranean conditions and improve irrigation control in a substrate culture. However, the model coefficients will have to be adjusted for specific climate and crop conditions.     

荔枝生产相关的水分生理指标远程监测研究

利用植物远程监测系统对荔枝园中的大气温湿度、土壤湿度、光照强度、大气蒸汽压差(VPD)等环境因子和茎干直径微变化、果实生长、叶片温度等树体生理指标进行了监测,发现该系统能准确及时并无伤害地记录他们的实时和周期性变化。据获得的数据初步表明,当果实处于快速膨大期,主茎的加粗生长明显缓慢,一旦果实采收后,茎干加粗生长则有一个迅速上升的变化;当土壤湿度高于33%(v/v)时,主茎的生长受到明显的抑制;VPD白天上升,夜间下降,当夜间VPD始终高于0,就形成所谓的“夜间干燥”,VPD的这种变化对荔枝主茎和果实的生长以及叶气温差(LATD)都有较大的影响,如主茎和果实的日间收缩量随VPD的增大而增大,夜间空气干燥不但抑制了主茎生长,也使日最大LATD下降。据此认为,果实和茎干的生长之间存在竞争关系,土壤湿度过高或者夜间空气干燥对荔枝的生长不利。     

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.     

核桃果实发育初期的水分状况

对在不同土壤水分条件下核桃枝条、叶片和果实水分含量动态与生长发育关系的研究结果表明,土壤供水不足时,树体水分亏缺,影响枝条生长和果实发育,降低坐果率.对有关水分生理指标测试表明,不同品种核桃叶水势(φW)日变化虽有差别,但相似,呈双峰型,叶φw愈低,晚上回升愈缓慢.叶φw日变化还受枝条上着生果实的影响,未着生果实枝条叶φw高于有果枝的.叶φw降低抑制光合产物的形成和累积.核桃蒸腾作用的日变化也呈双峰曲线,并与环境因子有密切关系.叶组织水分亏缺时,抗脱水能力强,具有一定的抗旱性能,晚熟品种优于早熟品种.     

Effects of irrigation frequency and scheduling on fruit production and radial fruit cracking in greenhouse tomatoes in soil beds and in a soil-less medium in bags

The effects on yield and radial fruit cracking of 2 media (soil in beds and soil-less medium in bags) and 2 drip-irrigation frequencies (once and 4 times daily) were determined for 4 greenhouse tomato (Lycopersicum esculentum L. Mill.) cultivars. For plants grown in soil-less medium, 2 tensiometer-controlled, drip-irrigation scheduling methods were compared. ‘Michigan’—‘Ohio’ hybrid fruit cracked significantly more than the 3 remaining cultivars, but did not differ in production of total and No. 1 fruit. The amount and severity of fruit cracking was least from the soil-less, bag-cultured plants. Total mean fruit weight was greatest from soil-grown plants. Although no differences in cracking occurred in the fruit from soil-less, bag-cultured plants, those whose irrigation was based on soil-less medium tensiometer readings produced lower total mean fruit weight than those whose irrigation was based on soil tensiometer readings. Number and weight of defective fruit was lowest from plants grown in soil-less medium and whose irrigation was based on soil tensiometer readings, and greatest from soil-grown plants. Fruit cracking was reduced by increasing the irrigation frequency from 1 to 4 times daily.     

The effect of root restriction on the incidence of blossom-end rot in bell pepper (Capsicum annuum L.)

Summary

Water and calcium uptake are important factors affecting the incidence of fruit blossom-end rot (BER) in tomato and pepper. In the present study an attempt was made to manipulate these factors by severe root pruning and to examine the effect on BER in greenhouse-grown bell pepper (Capsicum annuum L., cv. Mazurka). Pepper plants were transplanted, with the root system split into four separated compartments, each containing a single root quarter. Removal of half, or three quarters, of the root from fruit-bearing plants significantly reduced fruit BER incidence compared with plants with intact roots, especially in fruits which were at the rapid expansion stage at the beginning of the treatments. Removal of three quarters of the root reduced midday leaf water potential, stomatal conductance, and plant height. The number and weight of fruits were not affected by these treatments. Root pruning caused only a slight reduction in stem sap flow, as measured by the heat pulse technique. Calcium concentrations in the distal part of fruits from quarter-root-plants were higher than in fruits from non-pruned plants, whereas magnesium and potassium concentrations were not affected. On the other hand, in the leaves, calcium, magnesium and potassium concentrations were all reduced by root pruning. The K/Ca ratio decreased in the blossom-end of the fruits and increased in the leaves of root-pruned compared with control plants. The results suggest that root pruning did not affect the total uptake of calcium, apparently driven by transpiration, but did enhance calcium partitioning to the developing fruit. Root pruning also affected calcium distribution within the fruit and therefore attenuated BER incidence.     

Effects of day and night humidity on yield and fruit quality of glasshouse eggplant (Solarium melongena L.)

A spring and an autumn crop of eggplant (Solanum melongena) were grown under natural light conditions in a glasshouse at different day and night humidities. A high or low humidity by day was combined with either a high or low humidity by night. Vapour pressure deficits (VPD) achieved over the period in which the treatments were applied ranged from 0.44 to 1.18 kPa by day, from 0.24 to 0.91 kPa by night, with a 24 h mean from 0.34 to 0.99 kPa. The rate of plant development was unaffected by humidity. Fruit yields were reduced by continuously low VPD compared with the other treatments. The yield reduction could be attributed to fewer fruits being picked. Mean fruit weight was higher at high humidity by day. Continuously high VPD increased calyx withering, low VPD had no detrimental quality effects but promoted the incidence of Botrytis cinerea.     

设施栽培对油桃营养生长及果实生长发育的影响

设施内油桃的树体生物量(未含果实)较露地增加66.2%。单株全年新梢总长度增加1.0倍,总叶面积增加87.1%,比叶重(SLW)减小,根冠比下降。设施栽培加剧了新梢生长和果实生长对光合产物的竞争。果实生长对设施栽培的反应主要表现在Ⅰ期、Ⅲ期延长,Ⅱ期缩短,果实整个发育期延长10～15d,各期平均长度(天数)与夜间温度呈显著负相关(r=-0.9150)。设施栽培使果实普遍增大,主要原因是果实生长Ⅰ期设施内夜温较低,促进果肉细胞分裂。     

Effects of greenhouse cooling method on growth,fruit yield and quality of tomato (Solanum lycopersicum L.) in a tropical climate

A tomato (Solanum lycopersicum L.) crop was grown in four greenhouses during the dry season 2005/06 in Central Thailand. Sidewalls and roof vents of two greenhouses were covered with nets and these greenhouses were mechanically ventilated when air temperature exceeded 30 °C (NET). The other two greenhouses were covered with polyethylene film and equipped with a fan and pad cooling system (EVAP). Overall mean air temperature was significantly reduced by 2.6 and 3.2 °C (day) and 1.2 and 2.3 °C (night) in EVAP as compared to NET and outside air, respectively. Temperature maxima in EVAP averaged about 4 °C lower than in NET and outside. The relative humidity was around 20 and 30% (day) and 10 and 15% (night) higher in EVAP than in NET or outside, respectively. Vapour pressure deficit averaged 0.25 kPa in EVAP, 1.03 kPa in NET and 1.48 kPa outside. The crop water-consumption was significantly lower in EVAP (1.2) than in NET (1.8 L plant⁻¹ day⁻¹), which is ascribed to reduced transpiration in EVAP. Total fruit yield was similar in NET (6.4 kg plant⁻¹) and EVAP (6.3 kg plant⁻¹). The quantity of undersized (mostly parthenocarpic) and blossom-end rot (BER)-affected fruits was reduced in EVAP. However, the proportion of marketable yield was significantly higher in NET (4.5 kg plant⁻¹) than in EVAP (3.8 kg plant⁻¹), owing largely to an increased incidence of fruit cracking (FC) in EVAP. Higher FC but lower BER incidence coincided with higher fresh weight and Ca concentration in the fruits in EVAP. It is concluded that in regions with high atmospheric relative humidity evaporative cooling without technical modifications allowing dehumidification will not improve protected tomato production.     

李的裂果机制及防止措施

 研究李果皮组织细胞生长以及水分和可溶性固形物( TSS) 与裂果发生的关系, 对裂果发生的组织解剖特点进行了观察, 探索了喷施硼砂溶液、氢氧化钙溶液以及搭建塑料大棚等措施防止裂果发生的效果。研究结果如下: 1. 解剖学观察和显微测量表明, 绥李3号果实开裂的直接原因为果实外皮层与内部薄壁组织细胞生长不协调所致。与吉林6号和绥棱红相比, 绥李3号果实在快速生长期内部薄壁组织细胞生长速率显著过大( P < 0.05) , 而表皮细胞生长缓慢或停止。加之其表面纹饰空隙较大容易形成潜在突破口, 这样内外相互作用致使果实开裂。2. 裂果的可溶性固形物含量显著高于正常果( P < 0.05) 。3. 喷施硼砂可以减轻裂果, 但喷施氢氧化钙溶液无明显效果。4. 果实临近成熟时(8月初) , 土壤含水量与裂果程度呈正相关( P < 0.05) ; 搭建塑料大棚并在周围挖排水渠可以有效地减少绥李3号果实开裂, 说明水分是影响绥李3号裂果的主要驱动因子。     

温光处理对温室彩椒生长发育及产量的影响

为筛选出适宜彩椒生长的最适温度和光照,以彩椒品种Helsinki Rz为材料,采用裂区试验设计,研究了不同温光条件对彩椒生长、叶片光合特性及产量的影响。试验结果表明,在自然光照+1盏补光灯与自然温度+水暖加温的温光组合(W2G2)条件下,温室彩椒植株的茎粗、叶面积、地上部和根系干质量明显较高;植株的净光合速率、蒸腾速率、气孔导度和胞间CO2浓度最大;产量最高,可达8.80 kg/m2,显著高于其他处理。     

几个陇椒品种在喀什温室的引种试验

为了筛选出适合喀什日光温室栽培的辣椒品种,引进陇椒系列的3个品种在喀什地区疏勒县温室进行品种比较试验。通过植株生长、果实性状和前期产量对品种进行评价,结果表明:3个品种植株高大、茎秆细弱、生长旺盛,果实均为皮薄微辣有螺旋,果长20cm以上,单果重40g左右,前期产量达到1200～1500kg/667m2,参试的3个品种均可作为喀什温室栽培品种。     

Modelling the effect of air vapour pressure deficit on leaf photosynthesis of greenhouse tomatoes: The importance of leaf conductance to CO2

Summary

The response of photosynthesis of leaves of greenhouse tomato plants to leaf position and vapour pressure deficit (VPD) was studied by modelling the effect of these on leaf conductance to CO₂. The study was carried out in Avignon (southern France) on well-irrigated plants during spring and summer seasons, with VPD ranging from 0.7 to 3.4 kPa at midday, while the 24 h mean ranged from 0.6 to 1.8 kPa. Net photosynthesis (Pn) was measured on single leaves placed at three levels defined by the leaf position, and under different CO₂ concentrations in the range of 200 to 1100 µmol mol^–1. A model for leaf photosynthesis was used to evaluate the leaf conductance to CO₂ transfer. The leaf conductance to CO₂ transfer was maximum for top level leaves, and decreased with leaf depth in the canopy. Leaf conductance at the upper level was reduced when air VPD exceeded a threshold value of 1 kPa.     

Fruit Cracking in Mango (<Emphasis Type="Italic">Mangifera indica</Emphasis> L.) cv. ‘Dashehari’

The mango (Mangifera indica L.) is native to South and Southeast Asia, from where it has been distributed worldwide to become one of the most cultivated fruits in the tropics. It is the national fruit of India. In India, harvest and sale of mangoes take place during March-May and the fruits have high economic value in India. Studies were first time conducted on mango fruits to observe the severity of fruit cracking incidence. The stone was exposed in case of longitudinal type cracking and never exposed in star type cracking. The longitudinal cracking was 3.8, 3.4 and 1.7 % and star type cracking was 0.3, 1.8 and 0.02 % during 2009, 2010 and 2011, respectively. The lesser pulp thickness and higher stone weight in fruit cracked samples may have responsible for fruit cracking. There was a close relationship between fruit cracking and 3 months average weather conditions. The maximum temperature had positive relation with total fruit cracking.