Growth,stomatal resistance,and transpiration of Aloe vera under different soil water potentials

Aloe vera (Sábila) is used in folklore medicine and commercial cosmetology products in many countries. Little is known about the plant's physiological, growth, and yield responses under different irrigation regimes. The plant has a crassulacean acid metabolism (CAM) that allows water conservation within the tissue, and therefore, resistance to high water stress. A. vera plants were submitted to different irrigation regimes in a greenhouse experiment to evaluate the response of the physiologic processes such as stomatal resistance and transpiration as well as leaf growth and yield. The experiment consisted of three irrigation regimes under a completely randomized design. No initial effect on stomatal resistance or transpiration was exhibited, but as time elapsed changes in these variables were noted. We suggest that the high water content in the parenchyma maintains stomatal opening despite water stress. In a subsequent period, the leaves that were submitted to water stress at the beginning, showed stomatal opening reduction related to low soil water potential. The low soil water potential reduced leaf weight, plant growth rate, and leaf number, mainly in leaf growth during the experiment confirming the sensitivity of new leaves to water stress. The results suggest that the low leaf temperature increases stomatal resistance, decreases plant and leaf growth rates. This behavior is opposite to other CAM species in semiarid condition.     

外源钙对镍胁迫下水稻幼苗抗氧化酶活性及膜脂过氧化的影响

研究了外源钙（Ca2+）对镍胁迫下水稻叶片组织超氧化物歧化酶（SOD）、过氧化氢酶（CAT）、过氧化物酶（POD）和抗坏血酸过氧化物酶（APX）的活性、H2O2和丙二醛（MDA）含量以及质膜电解质渗透的影响,以探讨钙缓解植物镍毒性的生理机制。0.1 mmol/L镍（Ni2+）胁迫下水稻叶片组织SOD、CAT和APX活性明显下降,POD活性明显上升,H2O2和MDA含量、电解质渗漏率显著增大,说明镍诱导了细胞发生明显的氧化损伤和膜脂过氧化;钙提高了镍胁迫下叶片组织中SOD、CAT、POD和APX活性,显著降低了H2O2、MDA含量和电解质渗漏率,且10 mmol/L Ca2+处理的抗氧化酶活性上升的程度和H2O2、MDA含量和电解质渗漏率下降的程度比5 mmol/L Ca2+处理的大。提示钙通过促进镍胁迫下水稻叶片组织抗氧化酶活性,增强活性氧清除能力,维持细胞膜结构的稳定,是钙减轻镍对水稻毒性的生理机制之一。     

缺乏不同营养元素对剑麻幼苗生长和养分含量的影响

探究不同营养元素N、P、K、Ca、Mg缺乏对龙舌兰麻H.11648幼苗生长和养分含量的影响.通过砂培试验,设置了缺氮(-N)、缺磷(-P)、缺钾(-K)、缺钙(-Ca)、缺镁(-Mg)处理,调查了幼苗的株高、根长、叶片数、地上部和根系生物量、叶片和根系养分含量.结果表明:-N和-Ca处理剑麻幼苗株高、叶片数、地上部和根系干重均明显减小,其它缺素处理影响不明显.各缺素处理剑麻植株叶片和根系相应元素含量均降低.-K、-Ca处理植株含N量降低,-N、-K处理植株含P量明显增加,-Mg处理植株含K量以及-K处理植株含Ca量也明显增加,而-N处理植株含Mg量明显降低.说明N、P、K、Ca、Mg缺乏对剑麻幼苗生长和叶片养分含量均造成一定程度的影响,但影响程度不同,缺氮影响最大,缺钙次之.     

Potato top growth as influenced by temperatures

A study was conducted to establish a growth rate response of potato plant (Solanum tuberosum L.) tops to exposure to 72-hr periods of six constant temperature treatments (10, 15, 20, 25, 30, 35°C) and to determine a thermal optimum for vegetative potato growth rates. The plants were maintained under “no stress” soil moisture conditions throughout the study. The temperature treatments were accomplished by inserting the plants into a growth chamber for 72 hours at selected temperatures. Maximum growth (as measured by percent change in leaf area) occurred at 25°C with temperature growth differences significant at the 5% level. Plant height measurements (percent change occurring during treatment time) showed maximum stem elongation at 30°C during an early growth stage and 25°C during stage 2 (4 weeks later). Predictive models developed from the data indicate maximum rates of leaf area increase in both growth stages occur at 24.7°C and that maximum rates of stem elongation occur at 31.3 and 27.4°C for growth stages 1 and 2, respectively. Leaf water potential and stomatal resistance measurements taken at the end of each treatment period indicated that no water stress occurred.     

The potential use of plant physiological responses to water stress as an indication of varietal sensitivity to drought in four potato (Solanum tuberosum L.) varieties

Four potato varieties were subjected to water stress under controlled conditions. Leaf relative water content, leaf diffusive resistance, and photosynthesis were measured on stressed and unstressed plants during a stress period and during the recovery period following stress relief. Subsequent to the stress, plants were grown to maturity with optimal water supply. Mature plants were harvested and tuber yield and haulm production measured. Stressed plants of all varieties exhibited an increase in leaf diffusive resistance and a decrease in relative water content, transpiration, and photosynthesis as soil moisture decreased. Significant varietal differences in leaf diffusive resistance of stressed plants are apparent and offer promise for development of a screening technique for varietal sensitivity to drought based on stomatal response to water deficits.     

茉莉酸甲酯对武运粳24和宁粳3号灌浆早期高温胁迫生理特性的影响

以武运粳24和宁粳3号两个常规粳稻品种为材料,采用桶栽方式,研究高温条件下外源茉莉酸甲酯(MeJA)在灌浆早期对水稻生理特性及产量的影响。结果显示,喷施外源MeJA可以提高植株体内可溶性糖的积累量,维持膜的渗透平衡;外源MeJA通过增加叶片的气孔导度(G_s)和蒸腾速率(T_r),降低水稻的叶温及穗温;MeJA通过减轻高温对光合系统的损害,进而提高PSⅡ的最大光量子产量(F_v/F_m)、实际光化学效率(Φ_(PSⅡ))、光合电子传递速率(ETR)及分配给光化学反应的光能(P_r)比例,并最终提高净光合速率(P_n)。高温条件下,武运粳24中超氧化物歧化酶(SOD)、过氧化物酶(POD)的活性降低,而宁粳3号中的SOD、POD酶活性在高温后期则高于常温处理,而喷施MeJA能提高两品种SOD和POD两种酶在高温处理后期的活性,并降低丙二醛(MDA)的后期积累量,维持膜稳定性。综上所述,在高温条件下,MeJA可以有效降低水稻植株温度,有效缓解高温胁迫对植株生理生化过程的伤害,并通过提高千粒重和结实率减轻高温导致的产量损失。     

Photosynthetic components associated with differential senescence of maize hybrids following ear removal

The effect of ear removal on carbon exchange rate (CER), leaf resistance, transpiration and internal CO₂ concentration of leaves for two field-grown maize (Zea mays L.) hybrids was determined using a portable photosynthesis system. Ears were removed 15 days after anthesis and measurements were made at intervals during grain development on the first leaf above the ear. Leaf CER and transpiration of earless cv. B73 × Mo17 plants were lower than controls by 4 days after ear removal (DAER) and were not detectable by 18 DAER. In contrast, ear removal from cv. FS854 plants did not affect leaf CER or transpiration relative to eared controls until 9 DAER, and leaves retained 20% of maximum CER and transpiration by 29 DAER. The decline in CER in both hybrids did not appear to be due to stomatal closure, as initial internal CO₂ concentrations were sufficient to support adequate CER. The levels of CER, transpiration, and leaf resistance were consistent with visual estimates of leaf senescence.Grain harvested from the eared plants used for CER measurements showed that FS854 plants had more (23%) and heavier (4%) kernels than B73 × Mo17 plants. For FS854, the larger kernel number of comparable weight was attributed to the maintenance of a relatively higher level of leaf photosynthesis during the later stages of grain fill. The differences in CER and visual ratings indicate that the rate of leaf senescence following ear removal may be useful in identifying hybrids with late-season photosynthetic capabilities and high production potential.     

Growth and Nutrient Accumulation of Winged Bean and Velvet Bean as Cover Crops in a Subtropical Region

We examined biomass dry matter and nutrient uptake of live plant parts, leaf area index, and litter of winged bean (Psophocarpus tetragonolobus) and velvet bean (Mucuna pruriens) 12, 18, 24 and 30 weeks after sowing (WAS). The two plants had similar leaf and stem+petiole biomasses. At 30 WAS winged bean had a significantly lower pod yield than velvet bean. Between 18 and 30 WAS, winged bean produced less litter than velvet bean due to differences in growth stages. The total mulch of live parts and litter of winged bean and velvet bean completely covered the ground by 18 and 12 WAS, respectively. Compared to velvet bean, the leaf and stem+petiole of winged bean had a significantly higher N concentration; significantly higher N uptake at 24 and 30 WAS; significantly lower C/N ratio; and significantly higher P, K and Mg concentrations. In winged bean, P uptake was significantly higher in the leaf at 30 WAS and in the stem+petiole at all harvesting times. The total biomass of the leaf, stem+petiole and litter of winged bean was 317–561 g DM m-², and their N content was 12.3–17.7 g m-². The total biomass of live parts and litter of winged bean might be sufficient to suppress weeds and increase soil N. Winged bean is an appropriate legume cover crop and green manure due to its longer growing period and superior ground-covering ability and high N input.     

Root signalling and osmotic adjustment during intermittent soil drying sustain grain yield of field grown wheat

A field study was conducted to investigate the effect of intermittent soil drying on resulting non-hydraulic and hydraulic root signals, leaf gas exchange, leaf growth, day of heading, leaf osmotic adjustment and yield of wheat grown in sand and loam soils in lysimeters. A 40-day-drought treatment was imposed when the flag leaf started to emerge and was terminated close to maturity. Soil water content and soil water potential of various soil layers were measured using the neutron moderation method and tensiometers, respectively. Soil drying in the top soil layers induced increase in both xylem and bulk-leaf abscisic acid (ABA) content and reduced the stomatal conductance and leaf growth even before a measurable change in leaf water potential could be detected in droughted plants when compared with fully watered plants. Further, heading and flowering occurred 4 days earlier in the droughted than in the well-watered plants before any loss in leaf water potential had occurred as compared with the fully watered plants. When more severe drought reduced the leaf water status, further accumulation of leaf ABA occurred and transpiration decreased in addition to gradual osmotic adjustment and senescence of older leaves. The osmotic adjustment sustained leaf turgor pressure during soil drying. At severe drought, the osmotic adjustment at full turgor in the flag leaves was 0.85 MPa. In sand, the kernel dry weight increased and as a result similar grain yield was obtained in both the treatments. In loam which had more water available than sand, no significant reduction in the final yield was induced by the drought. It is concluded that (1) non-hydraulic root signals caused early drought adaptation at mild water stress by reducing leaf growth and stomatal conductance and hastening of heading and flowering; (2) osmotic adjustment sustained turgor maintenance and hence the yield-forming processes during moderate and severe water stress.     

Differences in tolerance to infertile acid soil stress among germplasm accessions and genetic recombinants of the tropical forage grass genus,Brachiaria

Several Brachiaria species are the most widely grown forages in tropical America. A field study was conducted during two seasons (1994, wet and 1995, dry) in a medium-textured Oxisol at Carimagua, Colombia. The main objective of the study was to evaluate genotypic variation in plant attributes for tolerance to low fertility, acid soil stress conditions (pH 4.9) among germplasm accessions and genetic recombinants of Brachiaria. The entries included 43 genetic recombinants selected from a breeding population, four parental accessions and an additional eight germplasm accessions. Small amounts of fertilizer were applied at establishment (kg ha⁻¹: 40 N, 20 P, 20 K, 14 Ca, 12 Mg and 12 S). A number of plant attributes including forage yield, leaf area, shoot nutrient composition and shoot nutrient uptake were measured during both seasons. Significant genetic variation was observed in several plant attributes such as leaf area, shoot nutrient content, nutrient partitioning to leaves, shoot nutrient uptake, and forage yield in both seasons. Forage yield ranged from 59 to 343 g plant⁻¹ in the wet season and 5 to 174 g plant⁻¹ in the dry season. Correlation between forage yield and shoot nutrient uptake indicated the importance of nutrient acquisition, particularly of phosphorus (r=0.90; P<0.0001), for adaptation to infertile acid soil stress. Two genetic recombinants (BRN093/3009, FM9201/1873) were productive when grown under infertile acid soil stress in both wet and dry seasons. But, neither of these two recombinants is highly resistant to xylem-feeding insects known as spittlebugs (Homoptera: Cercopidae). One spittlebug-resistant genetic recombinant (BRN093/1371) exhibited several desirable attributes such as superior leaf area and leaf biomass, greater N content in leaves, and greater partitioning of N and P to leaves that could contribute to adaptation and persistence in these soils. This recombinant is being utilized in a breeding program to develop superior Brachiaria lines.     

苗期甘蔗对干旱胁迫的反应

在砖红壤条件下,苗期甘蔗（Sarcharum oficinarumL.）植株对不同程度的水分胁迫反应不同。结果表明,在该土壤条件下,随着水分胁迫加强,叶片数、株高和植株的鲜重、干重呈减少的趋势,叶片叶绿素含量减少,细胞质膜透性增大,净光合速率下降,蒸腾速率加快,脯氨酸含量上升。但在轻度水分胁迫与正常供水的处理差异不明显。可见,在轻度水分胁迫时,不会明显影响甘蔗正常生长以及干物质的积累,且能达到节约用水灌溉的目的。     

Rice Flag Leaf Physiology,Organ and Canopy Temperature in Response to Water Stress

Abstract

Using two rice cultivars, the effect of severe, mild and no water stress, W3, W2 and W1, respectively, on flag leaf physiology, the ecological characteristics of canopy and organ temperatures were studied in 2008 and 2009. The grain yield was reduced under W3 due to decreased seed setting rate and 1000 grain weight but not under W2. Water stress had a significant effect on the flag leaf physiological characteristics along with the soluble sugar and amino proline content. Catalase and peroxidase activities, photosynthetic and transpiration rates, and stomatal conductance in W2 were significantly higher than in W3 and similar to those in W1. The organ and canopy temperatures were significantly higher in W3 than in either W1 or W2, and there was no significant difference between W1 and W2. This study clearly showed that water stress had a significant effect on leaf physiology, temperature of organs and canopy. Mild water stress (soil water potential maintained at -15- -20 kPa) could construct a population that is water-saving and resistant to heat stress. This facilitates access to a high yield as well.     

Diurnal and seasonal patterns of leaf gas exchange in bahiagrass (Paspalum notatum Flügge) growing in a subtropical climate

The objective of this study was to evaluate the seasonal and diurnal changes in leaf gas exchange in bahiagrass (Paspalum notatum) plants grown in an irrigated lawn. Carbon dioxide assimilation, transpiration, stomatal conductance, leaf temperature and leaf‐to‐air vapour pressure difference were measured during the daylight period from April 2003 to March 2004. The monitored environmental variables were photosynthetic photon flux density, air temperature, air relative humidity, photoperiod and sunshine rate. Factor and cluster analyses were used to select variables and to group months with similar physiological and meteorological characteristics, and three distinct periods were identified: (i) May to July: with low energetic availability, low leaf temperatures and low photosynthetic activity; (ii) September to January: with high energetic availability, high leaf temperatures and high photosynthetic activity; and (iii) April–March–August: a transient period with environmental and physiological characteristics showing intermediate values. The reduced plant development and growth during the winter season was in accordance to the lower photosynthetic activity recorded from June to August, this variable being a potential indicator of reduced phytomass production. The relationships between leaf gas exchange and seasonal growth are discussed.     

大豆籽实产量与其需水量之间关系的研究

大豆不同生育阶段的土壤水份状况与叶细胞浓度和叶水势关系的研究结果表明,上述水份生理指标与土壤湿度呈极显著的相关。不同灌水形式的试验和田间需水量的测定表明,大豆籽实产量71～260kg/亩的需水量为200～367m~3。在此范围内两者近乎直线正相关,当耗水量超过367m~3/亩时大豆籽实产量无明显增加。大豆在幼苗期、分枝期、花荚期、鼓粒期的适宜土壤湿度分别是田间最大持水率的70％、80％、80％、70％。     

水分胁迫对秋植花生结荚期同化物运输的影响

在秋播花生开花下针期至饱果成熟期给予不同程度的干旱处理,结果表明,无论是轻度、中度或严重干旱均影响果实的发育,使代谢源中的同化物向代谢库(荚果)中输出减少,植株叶片的含水量下降,蒸腾速率、光合速率及叶绿素含量降低,呼吸速率升高,同时花生经济产量降低。     

Measurement of cellular membrane thermostability to evaluate foliage heat tolerance of potato

Summary Cellular membrane thermostability of leaf tissue, measured by both leaching and direct conductivity, was used as an index for evaluating potato (Solanum tuberosum L.) leaf tolerance to high temperature. Experiments with eight genotypes showed that maximum differences between cultivars in response to temperature occurred at 52.5°C. The wide variability among the genotypes suggested that this index could be used to screen potato foliage for tolerance to heat. The results agreed well with visual scoring after exposing potted plants to 52.5°C. CPRI Publication No 854.     

Lower soil nitrous oxide emissions by a high lipid genetically modified perennial ryegrass line compared to its wild type

We describe an experiment where cattle urine was applied at a rate of 420 kg N ha⁻¹, equivalent to 10 L m⁻², to mesocosm swards of a high lipid genetically modified perennial ryegrass line (HME) and its wild type (WT). We measured N pools and fluxes in the plant and soil, soil microbial populations and N₂O production. HME plants produced 21% greater biomass than WT (p = .02), resulting in greater N uptake (27% higher in HME, p = .05). Urine N recovery in total plant biomass during the experiment in HME and WT swards were 54.7% and 33.9% respectively. The nitrification potential of soil was significantly lower (p = .01) in HME than WT. Partial least square-discriminant analysis using microbial gene abundance data indicated that HME and WT plant growth induced distinct microbial populations in the soil. These differences in plant soil microbial interactions between HME and WT swards resulted in significantly lower N₂O emissions from the HME sward. Total N₂O emissions over the 4 weeks after urine application was 38% lower (p < .03) in HME swards than in WT swards. The next step in this work is to identify the specific changes in HME traits that drive the reduction in N₂O.     

茶树根际土壤性质及氮肥的影响

本文报导了对盆栽茶树根际土壤性质的研究结果。经外力抖落后仍粘在根系上的土壤作为根际土壤,其余土壤为非根际土壤。施氮显著降低土壤pH、交换性K、Ca、Mg含量和盐基饱和度,增加水溶性铝、有机交换态铝和吸附羟基态铝的含量。与非根际土壤相比,根际土壤pH、交换性Ca、Mg和盐基饱和度明显降低,而交换性K高于非根际土壤。根际土壤的水溶性铝、交换性铝、交换性铝饱和度和吸附羟基态铝的含量显著高于非根际土。上述结果说明茶树根际土壤明显酸化,增强了土壤铝有效度。铝在茶树根际微域环境中的这种变化,可能在茶树吸收铝的过程中起着重要作用。     

Effect of high water temperature during vegetative growth on rice growth and yield under a cool climate

Global warming is likely to increase spring temperatures in regions with a cool climate. To examine the effects of this change on rice productivity, we exposed rice plants to a higher (by +2.7 to +2.8 °C) water temperature (T_w) during the vegetative growth period (for 35-50 days) under three levels of N fertilization. High T_w during vegetative growth made the heading stage occur 4-7 days earlier for all levels of N fertilization in both years. The crop growth rate during the treatment period was greatly enhanced by high T_w: by 51-82% in 2008 and by 49-62% in 2009. There was no T_w × N fertilizer interaction. This increased growth was associated with increased leaf expansion and increased canopy radiation capture rather than with increased radiation-use efficiency. However, the positive effect decreased during subsequent growth stages under all levels of N fertilization, leading to no significant differences in total biomass at maturity. High T_w during vegetative growth greatly reduced SPAD values during the grain-filling stage compared with SPAD values in the control T_w treatment, for all levels of N fertilization, and decreased leaf photosynthesis during the mid-grain filling stage. Grain yield was not significantly affected by high T_w at any N fertilizer level or in either year.     

土壤干旱对抗旱品种洛麦9133拔节期生理特性的影响

为揭示冬小麦拔节期对干旱胁迫的响应机制,采用盆栽试验对不同土壤干旱条件下洛麦9133拔节期的生理特性进行了研究.结果表明,拔节期叶水势、叶相对含水率、叶绿素含量、根系活力、蒸腾速率和光合速率均随土壤水分的减少而呈降低趋势;叶饱和亏、叶绿素a/b、叶片可溶性糖含量、脯氨酸含量、质膜透性、POD活性以及水分利用效率均呈增加趋势.这说明在干旱胁迫下,冬小麦通过降低水势、相对含水率、根系活力和蒸腾速率,增加渗透调节物质可溶性糖、脯氨酸含量和增强POD活性等生理上的变化以提高抗旱性,从而使其适应干旱逆境.