干旱过程中桃树茎和叶水势的变化

对田间生长的四年生桃树在充分灌水后的２２ｄ干旱周期内，分别在早上６：００和中午１４：００对茎、叶水势进行跟踪测定。同时测定了土壤充分湿润、中度水分亏缺及严重水分亏缺条件下上述指标的日变化。结果表明：在三种土壤水分 条件下叶水斩变化幅度在０．２ＭＰａ左右，差异不明显；而午间茎水势则由土壤充分湿润时的－０．６ＭＰａ降至土壤水分严重亏缺时的－１．８ＭＰａ，下降了１．２ＭＰdisplay status     

重水分胁迫下苹果树茎、叶水势的变化

对田间生长的3年生苹果树(红富士/M26/八棱海棠)在土壤干旱和湿润条件下的茎及叶片水势、气孔导度和净光合的日变化进行了测定。茎水势的测定采用外围新梢的直接取样测定法,以便同剪口处叶片的水势进行比较。测定结果表明,干旱土壤条件下的叶片水势稍低于土壤湿润的树,一般仅相差0.3MPa。而二个处理之间午间茎水势的差别则高达1～1.2MPa,表现出该指标对土壤干旱十分敏感。干旱条件下叶片气孔导度和净光合与土壤湿润的树也有明显差异。研究还发现,在水分严重亏缺条件下存在茎水势低于叶水势及一定压力下枝条木质部漏气现象。对这些现象的发生条件和可能原因进行了讨论。     

基于茎直径微变化的梨枣灌溉指标的初步研究

 研究了4年生酸枣砧梨枣（Ziziphus jujuba Mill.）植株主干茎直径微变化指标对土壤水势（SWP）变化的响应规律,以及与气象要素的关系。结果表明：土壤水势降低引起茎直径日最大收缩量（MDS）增大,日生长量（DG）、生长速率（TGR）和日最大值（MXTD）降低。在水分亏缺发展阶段和水分亏缺维持阶段,MDS和TGR的噪声信号（变异系数）较小,信号强度与噪声信号的比值较大,表明其对土壤水势变化反映敏感。此外,MDS、TGR与潜在蒸散量（ET₀）、正午水汽压亏缺（VPD_md）等气象因子的相关性显著,均能反映大气的干旱程度,因此TGR和MDS可作为梨枣水分亏缺的诊断指标。     

梨树在自然水分亏缺下的生理反应

１９９４～１９９６年对梨树在自然水分亏缺和水分充足条件下的主要水分生理参数、气孔相对开张度（ＲＳＯＤ）、蒸腾速率（Ｔｒ）和光合速率（Ｐｎ）进行了比较研究。结果表明，梨树属于低水势耐旱类型，在自然水分亏缺下，其叶水势（ψｗ）显著降低，膨压（ψｐ）明显增高，而ＲＳＯＤ、Ｔｒ和Ｐｎ则无显著变化。梨树具有明显的渗透调节和一定的弹性调节作用，在中度水分亏缺下，其渗透调节能力△π１００或△π０分别为０．４４ＭＰａ和０．７７ＭＰａ，弹性调节能力△｜β｜和△εｍａｘ分别为２．７８和３．１９。另外，在自然水分亏缺下，梨树叶片还具有较强的保水能力，反映在基本无变化的膨压消失点的相对含水量（Ｒ０）、叶表面水分散失率（ＷＬ０）和明显高于ＣＫ的一定ψｗ下的相对含水量（Ｒ）值以及无灌溉园较高的εｍａｘ或｜β｜等方面。     

中亚热带地区橘园坡地水分动态监测研究

为掌握中亚热带季节性干旱地区农业水分生态特征,进行了3 a田间实测。数据说明橘园坡地水分状况随年降水周期和坡位高低变化。0~150 cm土壤贮水量大致分为盈余期、消耗期和补充期3个阶段。土壤水势变化与贮水量3阶段相对应,总体由大变小再回升,只是土体空间从上而下,水势值增大,变幅减小,120 cm土层以下近乎常年稳定,0~120 cm坡下土层湿润程度高于坡上。在4个水势段出现频率中,水势较高的水势段出现频率越大,顺序为饱和湿润亏缺干旱。饱和与湿润段出现频率比例总体上底土心土表土,坡下坡上;低水势干旱段主要出现在橘园坡上、土壤上层和伏秋干旱季节。橘园地坡地对降水分配有一定的滞后作用,坡上渗漏总量高于坡下,为分析水文生态提供了依据。     

叶面喷施抗蒸剂对苹果树水分状态的影响

研究了叶面喷施抗蒸剂对盆栽苹果水分状态的影响。结果表明，抗旱剂一号（主要成分为黄腐酸）可明显降低树体蒸腾（最低时为对照的３９．２１％）提高气孔阻力（最大时为对照的２４３．９６％）和叶片水势（一般比对照提高０．２－０．４ＭＰａ，最大０．７ＭＰａ）并对叶温未产生明显的影响（变化一般小于１℃）有效作用期长达１５ｄ以上，在果树旱期喷施，可明显改善树体水分状态，腐殖酸效果不明显。     

叶面喷施抗蒸剂对苹果树水分状态的影响

研究了叶面喷施抗蒸剂对盆栽苹果水分状态的影响。结果表明：抗旱剂一号（主要成分为黄腐酸）可明显降低树体蒸腾（最低时为对照的３９．２１％）、提高气孔阻力（最大时为对照的２４３．９６％）和叶片水势（一般比对照提高０．２－０．４ＭＰａ、最大０．７ＭＰａ），并对叶温未产生明显的影响（变化一般小于１℃），有效作用期长达１５ｄ以上。在果树旱期喷施，可明显改善树体水分状态。腐殖酸效果不明显。     

桃枝条梢端生长及其与温度,叶水势和比叶重关系的研究

以金冠、汉瑞、红港、卡尔红为试材，探讨了桃枝条梢端生长与环境温度、叶水势和比叶重之间的关系及其昼夜变化规律。表明：在试验条件下枝条梢端生长速率与环境温度呈显著正相关，与一天中早、晚碳水化合物积累也呈显著相关，而与叶片水势变化无关。梢端生长速率昼夜总的变化趋势与气温变化相吻合，最大值出现在平均气温最高的傍晚（１６：００～２０：００），最小值出现在平均温度最低的凌晨（０：００～８：００）。在２５±０．５℃恒温条件下，梢端生长速率最大值出现后，并不随即下降，而是保持这个生长速率直至午夜，尔后逐渐降至最低值。太阳升起后，生长速率又逐渐回升。     

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.     

水分胁迫对番茄幼苗生长影响的研究

水分胁迫对番茄幼苗的生长有严重的抑制作用。幼苗根、茎、叶干重及株高、茎粗、叶面积等形态指标同土壤水分张力(PF值)呈极显著负相关。幼苗叶片水势有明显的日变化,春季日变化呈三次曲线(S型)。叶片水势同土壤PF值呈极显著负相关。这是利用土壤PF值进行番茄苗期水分管理的依据。叶片相对含水量、水分饱和亏、自由水、束缚水含量,细胞汁液浓度也同土壤PF值显著相关。土壤水分亏缺增加,叶片净光合率下降,游离氨基酸含量升高,硝酸还原酶活力降低。根据本试验结果认为,番茄幼苗从分苗到定植,土壤PF值维持在1.9—2.2范围内,幼苗生长健壮。     

Plant growth,water relations and transpiration of two species of African nightshade (Solanum villosum Mill. ssp. miniatum (Bernh. ex Willd.) Edmonds and S. sarrachoides Sendtn.) under water-limited conditions

The adaptation to drought stress of two African nightshade species, Solanum villosum and S. sarrachoides was investigated in pot and field experiments between 2000 and 2002. Two genotypes of S. villosum (landrace and commercial) and one accession of S. sarrachoides were grown under droughted, moderate stress and well-watered conditions. Leaf expansion, stem elongation and transpiration began to decline early in the drying cycle with fraction of transpirable soil water (FTSW) thresholds of 0.46–0.64. Osmotic adjustment (OA) of both species was in the range of 0.16–0.19 MPa and could not maintain positive turgor below water potentials of −1.80 to −2.04 MPa. The responses evaluated were similar in the three genotypes suggesting similar strategies of adaptation to drought stress. Under field conditions, the S. sarrachoides accession showed a higher leaf area than the S. villosum commercial genotype. It is concluded that the three African nightshade genotypes have limited OA capacity and adapt to drought mainly by regulating transpiration. This was achieved by reduction of leaf area. In general, it is necessary to maintain FTSW above 0.5–0.6 to prevent decline in leaf expansion, stem elongation, and transpiration.     

短期土壤干旱对苹果叶片光合速率日变化的影响

以盆栽2年生的金矮生为试材研究了短期土壤干旱对苹果叶片光合速率日变化的影响以及光合速率日变化与叶片水势日变化的关系.短期土壤干旱明显改变了苹果叶片光合速率的日变化进程.夏、秋季节短期中度土壤干旱导致叶片产生“午休”现象.“午休”发生时先表现为气孔限制,后为非气孔限制.叶片水势与光合速率、气孔导度呈阈值关系,阈值水势为-2.15MPa,叶片水势降至阈值之下,光合速率,气孔导度迅速降低,但叶片水势的日变化与光合速率的日变化没有明显的关系.     

The effect of irrigation and crop load on stem water potential and apple fruit size

Summary

The effect of irrigation rate under various crop loads on the fruit size of apple (Malus domestica Borkh cv. Golden Delicious) was investigated in three field experiments in 1993–1995. During the first two years the field experiments evaluated the effects of various crop loads on yield, fruit size and midday stem water potential under 40% deficit irrigation. In 1995, the effects of five irrigation levels (0.42–1.06 of USDA Class A evaporation pan) and four crop loads (100–450 fruits per tree) were studied in a factorial experiment. Midday stem water potential increased with irrigation level and decreased with crop load in 1993 and at the lowest irrigation level in 1995. Daily fruit growth rate decreased with midday stem water potential in 1993 and at the lowest irrigation level in 1993. The effect of crop load on fruit growth rate was associated with limited soil water availability. A reduction in yield and average fruit size were associated with midday stem water potentials lower than –1.3 MPa. Taking an additional 0.1 MPa as a safety factor, –1.2 MPa could serve as a reasonable threshold for irrigation control in the orchard.     

The response of different almond genotypes to moderate and severe water stress in order to screen for drought tolerance

In order to screen almond genotypes for drought tolerance, three different irrigation levels including moderate and severe stress (Ψs = −1.2 and −1.8 MPa respectively) and a control treatment (Ψs = −0.33 MPa) were applied for five weeks to six different cultivated almond seedlings. A factorial experiment was conducted with a RCBD which included 3 irrigations factors, 6 genotype factors and 3 replications. Seeds were prepared from controlled pollination of the bagged trees (after emasculation and flower isolation using isolator packets in the previous year). Genotypes included: homozygote sweet (Butte), heterozygote sweet (SH12, SH18, SH21 and White) and homozygote Bitter (Bitter Genotype). Leaf and root morphological and physiological traits including; midday relative water content, midday leaf (xylem) water potential, shoot dry weight and growth, total leaf area, leaf size, total leaf dry weight, specific leaf area, leaf greenness (SPAD), stomatal size and density, root and leaf nitrogen content and chlorophyll fluorescence were measured throughout the study. Results showed the six genotypes had different reactions to water stress but all genotypes showed an ability to tolerate the moderate and severe stresses and they showed different degrees of response time to drought stress. Almond seedling leaves could tolerate Ψ_w between −3 and −4 MPa in short periods. Water availability did not significantly affect stomatal density and size of young almond plants. The analysis of leaf anatomical traits and water relations showed the different strategies for almond genotypes under water stress conditions. Although almond seedlings even in severe stress kept their leaves, they showed a reduction in size to compensate for the stress effects. All genotypes managed to recover from moderate stress so Ψ_w = −1.2 could be tolerated well by almond seedlings but Ψ_w = −1.8 limited young plant growth. Leaf greenness, leaf size, shoot growth, shoot DW, TLDW and stomatal density were not good markers for drought resistance in almond seedlings. Root DW/LA, lower stomatal size and lower SLA might be related to drought resistance in cultivated almonds. Butte had the least resistance and White showed better performance during water stress while other genotypes were intermediate. Bitter seedlings showed no superiority in comparison with other genotypes under water stress conditions except for better germination and greater root DW which might make them suitable as rootstocks under irrigation conditions.     

Root growth,water relations and mineral uptake of young ‘Delicious’ apple trees treated with soil- and stem-applied paclobutrazol

Paclobutrazol (2R,3R + 2S,3S)-1-(4 chlorophenyl)-4,4-dimethyl-2-(1,2,4-trizol-1-yl) pentan-3-ol), at 25, 50 and 150 mg active ingredient, was applied as a soil drench or stem application to 1-year-old ‘Topred Delicious’ apples. Root growth measured as relative root surface area was reduced by both soil and stem applications. There was no significant difference in dry weight of the root tissue. The root-to-leaf-area ratio was significantly increased in paclobutrazol-treated plants.Water relations measured as leaf conductance and leaf water potential were significantly influenced by paclobutrazol. Leaf conductance was higher in paclobutrazol-treated plants when the plants were turgid, as well as under some water stress. Leaf water potential was significantly higher in treated plants.There were no significant differences in the total nitrogen, phosphorus, potassium and magnesium levels found in the leaf or root tissue.     

Phenology and drought affects the relationship between daily trunk shrinkage and midday stem water potential of peach trees

Summary

The relationship between maximum daily shrinkage in trunks (MDS), daily trunk growth (DTG), predawn water potential (Ψ_pd) and midday stem water potential (Ψ_stem) were studied in an irrigation experiment in peach trees. Control trees were irrigated to replace evapotranspiration, with trees receiving regulated deficit irrigation (RDI) watered at 35% of this rate during Stage II of fruit development and after harvest. The RDI trees were watered as controls during Stage III of fruit development. Minimum (Ψ_pd and Ψ_stem fell to –0.6.MPa and –1.2 MPa, respectively in RDI plots compared with –0.2 and –0.6 MPa in the controls. Trunk growth was less in the RDI plots than in the controls during drought. In contrast, MDS was higher when deficit irrigation was applied in the RDI trees. When site differences were considered the correlation between (Ψ_pd and accumulated trunk growth over an ample period was loose, while maximum daily shrinkage and midday stem water potential remarkably improved such a correlation. However, pooling all available data, the correlation between Ψ_stem and MDS was very poor (R²=0.44) and it substantially improved only when using data from specific phenological periods (i.e. R²=0.75). A seasonal drift in MDS values was observed and it was related to the seasonal changes in trunk growth rates, (i.e. highest shrinkage was found when growth rates were lowest). We concluded that phenology in combination with drought reduce the reliability of the water status information obtained from MDS.     

不同水氮水平对全立架露地栽培伽师瓜光合特性与水分利用效率的影响

探讨不同水氮水平对全立架露地栽培伽师瓜膨果初期挂果叶片光合特性及水分利用效率日变化的影响,以期为全立架露地栽培伽师瓜的合理水氮管理提供依据。田间试验于2012年在新疆全立架栽培伽师瓜主产县岳普湖县进行,灌水定额3个水平为:5250、6750、8250m3·hm-2;施氮量3个水平为:0、225、375kg·hm-2;灌溉方式为沟灌。结果表明:全立架露地栽培伽师瓜膨果初期挂果叶片净光合速率日变化及气孔导度日变化均呈双峰曲线型,不同水氮水平下净光合速率的峰值分别出现在11:00-13:00和17:00左右,光合"午休"出现在15:00左右。6750、8250m3·hm-2的灌水量提高叶片净光合速率、气孔导度和蒸腾速率的效果明显,且具有较低的气孔限制值,但8250m3·hm-2高灌水量的瞬时水分利用效率低于6750m3·hm-2灌水量6.7%;适宜的灌水量下,225、375kg·hm-2的施氮量可提高叶片的净光合速率和瞬时水分利用效率,且程度相近。适宜喀什地区全立架露地栽培伽师瓜膨果初期挂果叶片进行光合作用的水氮组合为施氮素225kg·hm-2、灌水6750m3·hm-2,其在获得较高净光合速率的同时,也有助于水分利用效率的保持。     

A comparative study of young ‘Thompson Seedless’ grapevines (Vitis vinifera L.) under drip and furrow irrigation. II. Growth, water use efficiency and nitrogen partitioning

The response of 3-year-old grapevines (Vitis vinifera L. cultivar ‘Thompson Seedless’) to furrow and drip irrigation was quantified in terms of water status, growth, and water use efficiency (WUE). Drip irrigation was applied daily according to best estimates of vineyard evapotranspiration while furrow irrigations were applied when 50% of the plant available soilwater content had been depleted. Drip and furrow irrigated vines showed similar water status (midday leaf water potential, Ψ₁) and shoot growth patterns throughout the season. Dry weight partitioning was not significantly different between treatments but root mass was somewhat larger for the furrow than drip irrigated vines. Nitrogen concentrations of the fruit and roots were significantly (P < 0.05) less for the drip irrigated vines when compared with the furrow treatment. Similar WUE (kg water kg⁻¹ fresh fruit wt.) were obtained for both treatments indicating that furrow irrigation was as efficient as drip irrigation under the conditions of this study. The data indicate that drip irrigation may increase the potential for control of vine growth by making vines more dependent on irrigation and N fertilization than furrow irrigation.