Changes in Free Amino Compounds during the Development of Two Wheat Cultivars Subjected to Different Degrees of Water Stress

The changes of total nitrogen and free amino compounds, exceptproline, in leaves, stems, roots and ears of the wheat cultivarsYecora and Generoso were followed during the development inthe field with and without irrigation. The time course of thesum of the amino compounds was similar in stems and roots, butwas different in the leaves and ears. The levels of particularcompounds for a given cultivar varied with plant development,organ and water stress. Glutamate, alanine, aspartate, and serinewere found at high concentrations in all organs, although theirproportion was substantially lower in the stems and roots whereglutamine and asparagine were also detected in considerableamounts. Large amounts of glutamine were also found in the ears.The concentrations of some compounds increased in the periodsof more severe water stress, although the concentration of totalnitrogen did not show a similar response. From correlationsbetween      

Carbohydrate and Proline Contents in Leaves, Roots, and Apices of Salt-Tolerant and Salt-Sensitive Wheat Cultivars1

Intra-specific variations in nonstructural carbohydrates and free proline were determined in leaves, apices, roots, and maturing seeds of two salt-tolerant cultivars (CR and Kharchia-65) and one salt-sensitive cv. Ghods of spring wheat (Triticum aestivum L.) grown in sand culture at various levels of salinity (0, 100, 200, and 300 mM NaCl and CaCl₂ at 5 : 1 molar ratio) under controlled environmental conditions. The levels of leaf, apex, and root ethanol-soluble carbohydrates, fructans, starch, and proline increased in line with elevating level of salinity in all three cultivars under investigation. The contents of proline, soluble and insoluble carbohydrates in the apex increased to levels exceeding those in the leaves and roots. Soluble carbohydrate content of salt-sensitive cv. Ghods was higher in the leaves, apices, and roots and lower in the maturing seeds than in the other cultivars at all levels of salinity except at 300 mM. The results show considerable variation in the amount of soluble, insoluble sugars, and proline among plant tissues and wheat genotypes in response to salinity. Higher soluble carbohydrates and fructan in leaves, roots and maturing seeds of stressed plants indicate that their accumulation may help plant to tolerate salinity. Salt-sensitive cv. Ghods accumulated less soluble sugars in the maturing seeds and higher soluble sugars in the apices, which might be used as an indicator in screening wheat genotypes for salinity tolerance.     

Biochemical Changes in Excised Leaves of Oryza sativa Subjected to Water Stress

Excised rice (Oryza sativa L. cv. Ratna) leaves were used to compare the changes in the levels of various biochemical intermediates and enzyme activities during senescence in turgid and water-stressed conditions. Chlorophyll, total protein and soluble protein content decreased but α-amino nitrogen content increased during the senescence of turgid leaves. In the leaves subjected to water stress, these changes were accelerated, the acceleration being greater with higher degree of water stress. Starch, soluble sugars, total carbohydrates and non-reducing sugar content decreased during senescence of turgid leaves. Water stress accelerated the changes in the levels of starch and non-reducing sugar, but the changes in the levels of soluble sugars and total carbohydrates were retarded. Reducing sugar content increased at first and then decreased in the turgid leaves, and water stress accelerated the change. The decline in the catalase activity and the increase in the peroxidase activity with time was faster in the water-stressed leaves than in the turgid leaves. Acid inorganic pyrophosphatase activity increased, but alkaline inorganic pyrophosphatase activity decreased during the senescence of turgid leaves, and such changes were accelerated by water stress. The results suggest that water stress does not accelerate all the processes connected with leaf senescence.     

Composition and Distribution of Free Amino Acids in Flatpea (Lathyrus sylvestris L.) as Influenced by Water Deficit and Plant Age

Drought-stressed flatpea (Lathyrus sylvestris L.) plants from8 to 22 weeks old were analysed for nitrogen, soluble proteinand free amino acids. An increase in nitrogen and free aminoacid concentrations and a decrease in soluble protein levelwere observed in roots of plants up to 16 weeks old. The cumulativeconcentration of free amino acids increased with drought stress.Tissue concentrations of 2, 4-diaminobutyric acid (1.6–2.6%of the dry weight) were highest in leaves. Levels increasedsteadily, nearly doubling, in leaves and stems between weeks10 and 16. Levels in drought-stressed leaves were, on average,11.9% higher than those of controls. Estimated concentrationsof a mixture of 4-aminobutyric acid and an unknown amino acidwere highest in stems, increased in this tissue with age andtended to increase in stems and leaves and decrease in rootsin response to water deficit. Levels of the mixture of homoserineand another unidentified amino acid were not influenced by ageor water status of the plants. Root concentrations of asparagine,arginine, glutamine, aspartate, and another prominent, unidentifiedamino acid increased with plant age and reached a peak at thetime of flowering (14 to 18 weeks). Only the concentration ofthe unknown compound was elevated following drought stress.Concentrations of valine, isoleucine, leucine, phenylalanine,and methionine also increased during this period and were elevatedin drought-stressed plants. Proline levels increased with plantage and drought stress, but proline accounted for only about10% of the total free amino acids in the drought-stressed plants. Key words: 2, 4-Diaminobutyric acid, drought, flatpea     

The Influence of Plant Water Deficit on Distribution of 14C-labelled Assimilates in Cacao Seedlings

The relationship between plant water status and distributionof ¹⁴C-labelled assimilates in cacao (Theobroma cacao L.) wasevaluated after ¹⁴CO₂ pulse labelling leaves of seedlings subjectedto varying levels of water deficiency. The proportion of ¹⁴Cexported by source leaves was strongly affected by seedlingwater status. An increasing proportion of labelled assimilatesremained in source leaves at both 24-h and 72-h harvests aswater stress intensity increased. Water stress reduced the distributionof exported label to leaves and to the expanding flush in particularbut increased the proportion of label in stems and roots. Theresults suggest that current photoassimilates may be temporarilystored in source leaves and stems of cacao seedlings duringperiods of plant water deficit. The stress-induced changes inpartitioning of labelled carbon were in concordance with changesin shoot to root biomass ratios, which was likely due to greaterreduction in growth of above-ground organs to that of roots. Theobroma cacao L, assimilate partitioning, cacao, ¹⁴C-photoassimilate, water stress, water potential     

Organ-dependent responses of Periploca sepium to repeated dehydration and rehydration

Plant responses to water deficit occur in a complex framework of organ interactions, but few studies focus on the effect of drought stress on all organs in a whole-plant. The effects of repeated dehydration and rehydration (DH) on physiological and biochemical responses in various organs of Periploca sepium Bunge (P. sepium) were investigated. The leaf relative water content decreased significantly during drought, but recovered and showed an increase when compared to well-watered control plants. The malondialdehyde (MDA) content increased in mature and old leaves, but decreased in young leaves, new stems and fine roots during drought, indicating that the young and vigorous tissues of a whole-plant are protected preferentially from the oxidative stress. Among all organs, the fine roots showed the highest levels of proline, total free amino acids (TFAA) and Na⁺, while the leaves showed the highest levels of total soluble sugars (TSS), soluble proteins (SP), Ca²⁺ and Mg²⁺. The response to DH differed in different organs, both in magnitude and in the type of solutes involved. Drought stress increased the contents of proline, TFAA, TSS, SP and K⁺ in all organs of P. sepium plants, while the accumulation amounts were obviously different among the organs. The storage starch in stems and roots plays an important role in providing carbohydrates for growth. Changes in Na⁺, Ca²⁺ and Mg²⁺ under DH presented a high degree of organ specificity. Our data indicates that response strategies are different between different organs; therefore, evidence the needs to integrate all the information in order to better understand plant tolerance mechanisms.     

Nodule activity and allocation of photosynthate of soybean during recovery from water stress

Nodulated soybean plants (Glycine max [L.] Merr. cv Ransom) in a growth-chamber study were subjected to a leaf water potential (psi w) of -2.0 megapascal during vegetative growth. Changes in nonstructural carbohydrate contents of leaves, stems, roots, and nodules, allocation of dry matter among plant parts, in situ specific nodule activity, and in situ canopy apparent photosynthetic rate were measured in stressed and nonstressed plants during a 7-day period following rewatering. Leaf and nodule psi w also were determined. At the time of maximum stress, concentration of nonstructural carbohydrates had declined in leaves of stressed, relative to nonstressed, plants, and the concentration of nonstructural carbohydrates had increased in stems, roots, and nodules. Sucrose concentrations in roots and nodules of stressed plants were 1.5 and 3 times greater, respectively, than those of nonstressed plants. Within 12 hours after rewatering, leaf and nodule psi w of stressed plants had returned to values of nonstressed plants. Canopy apparent photosynthesis and specific nodule activity of stressed plants recovered to levels for nonstressed plants within 2 days after rewatering. The elevated sucrose concentrations in roots and nodules of stressed plants also declined rapidly upon rehydration. The increase in sucrose concentration in nodules, as well as the increase of carbohydrates in roots and stems, during water stress and the rapid disappearance upon rewatering indicates that inhibition of carbohydrate utilization within the nodule may be associated with loss of nodule activity. Availability of carbohydrates within the nodules and from photosynthetic activity following rehydration of nodules may mediate the rate of recovery of N2-fixation activity.     

Changes in Sugar Content during Cold Acclimation and Deacclimation of Cabbage Seedlings

The relationship between freezing tolerance and sugar contentin cabbage seedlings was investigated. Seedlings exposed tonon-freezing low temperature (5 °C) acquired freezing tolerancedown to -6 °C. The degree of freezing tolerance increasedwith duration of exposure to low temperature (up to 10 d). Sucrose,glucose, fructose and myo -inositol were detected as solublesugars in cabbage leaves, and all soluble sugars, except formyo -inositol, and starch increased gradually during cold acclimationsuch that their levels were positively correlated with the degreeof freezing tolerance. The induced freezing tolerance was attributednot to ontogenetic changes but to cold acclimation. However,the induced freezing tolerance was lost after only 1 d of deacclimationat control temperatures, and this change was associated witha large reduction in sugar content. These results reveal that the sugar content of cabbage leavesis positively correlated with freezing tolerance. Brassica oleracea L.; cabbage; cold acclimation; deacclimation; freezing tolerance; sugars     

蒙古莸幼苗干旱致死过程中非结构性碳水化合物的变化

以一年生蒙古莸幼苗为对象,设置适宜水分、慢速干旱致死和快速干旱致死3个处理,研究不同干旱强度致死下蒙古莸幼苗各器官中非结构性碳水化合物(NSC,包括可溶性糖和淀粉)的含量变化及其分配规律.结果表明:慢速干旱致死胁迫下各器官可溶性糖含量与适宜水分组无显著差异.随时间的推移,茎可溶性糖含量先增加后减少,淀粉和NSC含量增加;粗根可溶性糖含量减少,淀粉和NSC含量增加;叶可溶性糖含量增加,淀粉和NSC含量减少.致死时(80 d),叶、茎、粗根和细根的NSC含量分别为6.2%、7.8%、8.3%和7.4%.快速干旱致死胁迫下,各器官可溶性糖含量均高于适宜水分处理组,而淀粉和NSC含量均低于适宜水分组.随时间的推移,根可溶性糖含量下降,淀粉和NSC含量上升;茎可溶性糖、淀粉和NSC含量均上升;叶可溶性糖含量上升,淀粉和NSC含量下降.致死时(30 d),叶、茎、粗根和细根的NSC含量分别为5.9%、6.6%、8.9%和7.7%.应对不同的干旱致死情况,蒙古莸幼苗各器官间非结构性碳水化合物呈现出不同的动态变化.在慢速干旱致死胁迫下,NSC优先为维持各器官生理代谢活动提供能量;而在快速干旱致死下,NSC主要以可溶性糖形式维持植物代谢,调节渗透势,促进吸水,应对急剧的干旱胁迫.     

Seasonal Concentrations of Non-structural Carbohydrates of Five Actinidia Species in Fruit, Leaf and Fine Root Tissue

To characterize seasonal patterns of carbohydrate concentrationsin Actinidia species from different natural habitats, leaf,fruit and fine root tissue samples from five species (A. arguta,A. deliciosa, A. chinensis, A. polygama and A. eriantha) werecollected over one season, and analysed for fructose, glucose,sucrose, myo -inositol and starch concentrations. Sucrose andstarch peaked in leaf tissue around flowering time. In fruit,hexose sugars and/or myo -inositol transiently increased earlyin development. Starch accumulated in fruit of all species,beginning sooner after anthesis in A. arguta and A. polygamathan in the other species. Sucrose accumulation coincided withonset of net starch degradation in A. arguta but was delayedin the other species. At final fruit sampling, concentrationsof glucose and fructose were greater than sucrose in all speciesexceptA. arguta . myo -Inositol concentrations constituted >10%of total sugars for most of the season in leaf and fruit tissuesof all species except A. polygama. Fine roots of A. arguta andA. polygama contained significantly more starch and sucrosefor most of the year than those of the other species. Observeddifferences in seasonal carbohydrate patterns may reflect differentnatural habitats, with A. arguta and A. polygama growing naturallyin colder climates than the other species. Transient accumulationof sugars in fruit during early stages of development has beenconsidered to act as primary osmoticum for cell expansion. However,the presence of only low sugar concentrations in A. erianthaquestions this hypothesis. Copyright 2000 Annals of Botany Company Actinidia arguta, Actinidia deliciosa, Actinidia chinensis, Actinidia eriantha,Actinidia polygama , kiwifruit, carbohydrates, fruit, leaves, fine roots, seasonal     

Frost De-acclimation of Barley (Hordeum vulgare L.) and Meadow Fescue (Festuca pratensis Huds.). Relationship between Soluble Carbohydrate Content and Resistance to Frost and the Fungal PathogenBipolaris sorokiniana (Sacc.) Shoem.

Plants of barley (Hordeum vulgare) and meadow fescue (Festucapratensis), two species differing in their susceptibility tothe fungal pathogen Bipolaris sorokiniana, were cold-acclimated.Changes in frost resistance, susceptibility to B. sorokiniana,osmotic potential, water content, and composition of low molecularweight sugars were studied in leaves over a period of 14 d duringsubsequent de-acclimation. Cold acclimation promoted resistanceto frost and the fungal pathogen in both species. Plants subjectedto de-acclimation lost their ability to withstand frost afterabout 24 h, but retained enhanced levels of resistance to thepathogen. This effect lasted longer in the less pathogen-resistantbarley than in meadow fescue. Changes in osmotic potential observedafter cold-acclimation and during dehardening were correlatedwith changes in frost resistance, but not with changes in susceptibilityto the pathogen. The same applied to changes in the low molecularweight sugar content in leaves of meadow fescue. In barley,cold-acclimation induced alterations in osmotic potential andthe subsequent increase in frost resistance was not correlatedwith variation in soluble carbohydrate contents. The resultsindicate that cold-acclimation induced changes in leaf waterpotential and that soluble sugar content is not involved directlyin the increased resistance to the pathogen which was observedafter cold acclimation. Copyright 2000 Annals of Botany Company Cold acclimation, de-acclimation, frost resistance, fungal pathogens, osmotic potential, prehardening, sugars     

盐胁迫条件下杨树盐分与甜菜碱及糖类物质变化

以抗旱耐盐性强的胡杨（Populus euphratica）和非抗盐的群众杨（P. popularis‘35-44’）为实验材料,研究了盐胁迫条件下盐分与甜菜碱、还原糖、蔗糖以及水溶性糖等细胞相容溶质的动态变化。两种杨树在盐处理期间表现出明显差异：群众杨下部叶片首先表现出盐害症状,处理后两周苗木上部叶片也出现盐害并脱落。而胡杨在试验期间仅下部叶片发黄脱落,盐处理15天后落叶量仅为16%。群众杨盐害症状的出现主要是由叶片中盐离子的大量累积所致。与之比较,胡杨拒吸Na+的能力及控制Cl-转运的能力均优于群众杨。另外,胡杨的耐盐性强于群众杨也与其有机溶质的变化有关。受到盐胁迫后胡杨根叶中甜 菜碱浓度显著提高,在处理后15天达到最高值,特别是叶片中甜菜碱的浓度提高了243倍,达到1*!899.8 μmol/L,根中甜菜碱含量也增加了9倍。此外,盐处理后胡杨叶和根中的还原糖、水溶性糖和蔗糖含量均呈明显上升趋势,分别在第4天和第15天达到峰值。与胡杨相反,耐盐性弱的群众杨在盐胁迫期间,叶中甜菜碱和糖含量并无显著提高,根中糖分水平还明显降低。由此可以得出结论,胡杨渗透调节能力高于群众杨,是其耐盐性强的重要生理基础之一。     

Triadimefon Protects Bean Plants from Water Stress through its Effects on Abscisic Acid

Triadimefon is a fungicide that has plant growth regulatingproperties. In beans (Phaseolus vulgaris L.) it significantlyreduced shoot weight, shoot length and leaf area, and rootsappeared whiter and thicker in the treated plants. Chlorophylland carotenoid levels were increased in the leaves, but triadimefondid not affect protein levels in either leaves or roots. Triadimefonreduced transpiration and protected the plants from drought.It increased leaf diffusive resistance indicating partial closureof the stomates, and treated plants maintained their water potentialswhile those of the controls declined. Osmotic potentials ofboth treated and control leaves fell, but values in the controlswere significantly lower than those from the treated plants.Three days after treatment with triadimefon in both water stressedand non-stressed plants the abscisic acid levels in the leavesof the treated plants were more than twice the levels of thecontrols. It appears therefore that the protection conveyedby triadimefon during water stress is mediated at least partially,via its effects on ABA levels in treated tissue. (Received October 12, 1985; Accepted January 8, 1986)     

Salicylic acid-induced adaptive response to copper stress in sunflower (Helianthus annuus L.)

The ameliorative effect of salicylic acid (SA: 0.5 mM) on sunflower (Helianthus annuus L.) under Cu stress (5 mg l⁻¹) was studied. Excess Cu reduced the fresh and dry weights of different organs (roots, stems and leaves) and photosynthetic pigments (chlorophyll a, b and carotenoids) in four-week-old plants. There was a considerable increase in Chl a/b ratio and lipid peroxidation in both the roots and leaves of plants under excess Cu. Soluble sugars and free amino acids in the roots also decreased under Cu stress. However, soluble sugars in the leaves, free amino acids in the stems and leaves, and proline content in all plant organs increased in response to Cu toxicity. Salicylic acid (SA) significantly reduced the Chl a/b ratio and the level of lipid peroxidation in Cu-stressed plants. Under excess Cu, a higher accumulation of soluble sugars, soluble proteins and free amino acids including proline occurred in plants treated with 0.5 mM SA. Exogenous application of SA appeared to induce an adaptive response to Cu toxicity including the accumulation of organic solutes leading to protective reactions to the photosynthetic pigments and a reduction in membrane damage in sunflower.     

Gas exchange and water relations of three <Emphasis Type="Italic">Vitis vinifera</Emphasis> L. cultivars growing under Mediterranean climate

Optical characteristics, contents of photosynthetic pigments, total soluble sugars, and starch, rates of gas exchange, chlorophyll (Chl) a fluorescence, and leaf water relations were analysed in three Vitis vinifera L. cultivars, Tinto Cão (TC), Touriga Nacional (TN), and Tinta Roriz (TR), grown in Mediterranean climate. Chl content was significantly lower in TC than in TN and TR leaves, while the Chl a/b ratio was higher. TR had the lowest net photosynthetic rate, stomatal conductance, and contents of soluble sugars and starch than TN and TC. In spite of low Chl content, TC showed the lowest photon absorbance and the highest photochemical efficiency of photosystem 2. TC had the lowest predawn and midday leaf water potential. The capability for osmotic adjustment was similar among cultivars and the calculated modulus of elasticity was higher in TC leaves. The typical lighter green leaves of TC seemed to be an adaptive strategy to high irradiance and air temperature associated to water stress.     

Changes in the water status and osmotic solute contents in response to drought and salicylic acid treatments in four different cultivars of wheat (<Emphasis Type="Italic">Triticum aestivum</Emphasis>)

Salicylic acid (SA) controls growth and stress responses in plants. It also induces drought tolerance in plants. In this paper, four wheat (Triticum aestivum L.) cultivars with different drought responses were treated with SA in three levels of drain (90, 60, 30% of maximum field capacity) to examine its interactive effects on drought responses and contents of osmotic solutes that may be involved in growth and osmotic adjustment. Under drought condition, the cultivars Geza 164 and Sakha 69 had the plant biomass and leaf relative water content (LRWC) greater than the cultivars Gemaza 1 and Gemaza 3. In all cultivars, drought stress decreased the biomass, LRWC, and the contents of inorganic solutes (Ca, K, Mg) and largely increased the contents of organic solutes (soluble sugars and proline). By contrast, SA increased the biomass, LRWC and the inorganic and organic solute contents, except proline. Correlation analysis revealed that the LRWC correlated positively with the inorganic solute contents but negatively with proline in all cultivars. SA caused maximum accumulations of soluble sugars in roots under drought. These results indicated that SA-enhanced tolerance might involve solute accumulations but independently of proline biosynthesis. Drought-sensitive cultivars had a trait lowering Ca and K levels especially in shoots. Possible functions of the ions and different traits of cultivars were discussed.     

Nodule Activity and Allocation of Photosynthate of Soybean during Recovery from Water Stress

Nodulated soybean plants (Glycine max [L.] Merr. cv Ransom) in a growth-chamber study were subjected to a leaf water potential (Ψ_w) of −2.0 megapascal during vegetative growth. Changes in nonstructural carbohydrate contents of leaves, stems, roots, and nodules, allocation of dry matter among plant parts, in situ specific nodule activity, and in situ canopy apparent photosynthetic rate were measured in stressed and nonstressed plants during a 7-day period following rewatering. Leaf and nodule Ψ_w also were determined. At the time of maximum stress, concentration of nonstructural carbohydrates had declined in leaves of stressed, relative to nonstressed, plants, and the concentration of nonstructural carbohydrates had increased in stems, roots, and nodules. Sucrose concentrations in roots and nodules of stressed plants were 1.5 and 3 times greater, respectively, than those of nonstressed plants. Within 12 hours after rewatering, leaf and nodule Ψ_w of stressed plants had returned to values of nonstressed plants. Canopy apparent photosynthesis and specific nodule activity of stressed plants recovered to levels for nonstressed plants within 2 days after rewatering. The elevated sucrose concentrations in roots and nodules of stressed plants also declined rapidly upon rehydration. The increase in sucrose concentration in nodules, as well as the increase of carbohydrates in roots and stems, during water stress and the rapid disappearance upon rewatering indicates that inhibition of carbohydrate utilization within the nodule may be associated with loss of nodule activity. Availability of carbohydrates within the nodules and from photosynthetic activity following rehydration of nodules may mediate the rate of recovery of N₂-fixation activity.     

Effect of flooding on tomato cultivars: The relationship between proline accumulation and other morphological and physiological changes

Flooding of the root system of tomato plants ( Lycopersicon esculentum ) caused cessation of leaf elongation, leaf epinasty, formation of adventitious roots, and increase in diffusive resistance associated with the wilting of leaves at the first stage of the stress. Upon development of adventitious roots, the wilted leaves regained their turgor and the diffusive resistance slowly decreased at a rate slower than that at which water potential increased. In the course of flooding, proline accumulated but after 11 days dropped back to the control level. The extent of proline accumulation in various tomato cultivars was positively correlated with the extent to which their leaf water potential dropped, but was not correlated with the changes in their diffusive resistance. Cultivars which accumulated the highest proline levels were those which showed the most severe injury, with only one cultivar as an exception. However, only in the cultivars producing high levels of proline was the return of leaf turgor followed by resumption of leaf elongation. In cv. 'Hosen', which was severely injured by the stress, but accumulated a low level of proline, leaf elongation was not resumed. The results suggest that proline accumulation is an indicator of the cultivar's sensitivity to dehydration associated with the flooding stress, and confirm the notion that proline may play a role in the post-stress recovery process.     

Compensation to simulated insect leaf herbivory in wild cotton (Gossypium hirsutum): responses to multiple levels of damage and associated traits

• Identifying the mechanisms of compensation to insect herbivory remains a major challenge in plant biology and evolutionary ecology. Most previous studies have addressed plant compensatory responses to one or two levels of insect herbivory, and the underlying traits mediating such responses remain elusive in many cases.
• We evaluated responses associated with compensation to multiple intensities of leaf damage (0% control, 10%, 25%, 50%, 75% of leaf area removed) by means of mechanical removal of foliar tissue and application of a caterpillar (Spodoptera exigua) oral secretions in 3‐month‐old wild cotton plants (Gossypium hirsutum). Four weeks post‐treatment, we measured plant growth and multiple traits associated with compensation, namely: changes in above‐ and belowground, biomass and the concentration of nutrients (nitrogen and phosphorus) and non‐structural carbon reserves (starch and soluble sugars) in roots, stems and leaves.
• We found that wild cotton fully compensated in terms of growth and biomass allocation when leaf damage was low (10%), whereas moderate (25%) to high leaf damage in some cases led to under‐compensation. Nonetheless, high levels of leaf removal (50% and 75%) in most cases did not cause further reductions in height and allocation to leaf and stem biomass relative to low and moderate damage. There were significant positive effects of leaf damage on P concentration in leaves and stems, but not roots, as well as a negative effect on soluble sugars in roots.
• These results indicate that wild cotton fully compensated for a low level of leaf damage but under‐compensated under moderate to high leaf damage, but can nonetheless sustain growth despite increasing losses to herbivory. Such responses were possibly mediated by a re‐allocation of carbohydrate reserves from roots to shoots.

     

Effects of Root Pruning on Translocation of Photosynthates in Phaseolus vulgaris L

Root pruning increased the level of ethanol soluble sugars inred kidney bean plants (Phaseolus vulgaris L. ) grown in aeratednutrient solution. However, the concentration gradient of thesesugars down the stem and its translocation velocity remainedunchanged. Removal of 50% of the roots had no effect on thetotal photosynthates exported from source leaves but the finaldistribution pattern of photosynthates was altered; less movingtoward the upper plant parts, and accumulation occurring inthe lower stems. Translocation velocity of photosynthates towardthe upper plant parts was drastically reduced by root pruning. Key words: Phaseolus vulgaris, Photosynthate translocation, Root pruning