Differential effects of benzyladenine on the ultrastructure of chloroplasts in intact bean leaves according to their age

Summary Primary leaves of intact bean plants (Phaseolus vulgaris) were treated with benzyladenine (BA) at different stages of growth. Changes in the ultrastructure of chloroplasts and the contents of chlorophyll, carotenoid, and protein (soluble and insoluble) in leaves with different treatments were followed and compared. When BA was applied from an early stage, it increased the chloroplast size and the number of grana per chloroplast without any pronounced effect on the grana size. When BA treatment was stopped at the early stage, these effects remained for a while and then diminished. When BA treatment was begun at a late stage, such marked effects were not observed, suggesting that only young leaves could respond to BA in that manner. However, the late treatment efficiently prevented the process of the last stage of leaf senescence characterized by disintegration of thylakoids with concomitant increase in the plastoglobule size. Chlorophyll, carotenoid, and insoluble protein contents per leaf followed similar changes in chloroplast length and the number of grana per chloroplast section.     

Increase in DNA Content of Primary Leaves of Phaseolus vulgaris upon Decapitation

Changes in DNA content of bean (Phaseolus vulgaris) primaryleaves after decapitation were investigated. When apical budswere removed at 11 d, DNA content per leaf increased by about20% at 15 d and then decreased in parallel with the controls.The RNA and chlorophyll contents, fresh weight, and leaf areaexpressed on a single leaf basis changed in the same manneras the DNA content in response to decapitation. But when bothapical and lateral buds were removed, all these values continuedincreasing during the test period. Thus, growing lateral budsand apical buds have the same effect on the DNA change in primaryleaves as that due to ageing of the leaves. Cell number perleaf was not increased by any treatment, indicating that theobserved increase in the DNA content of primary leaves is ascribableto an increase in DNA per cell. Next, the whole shoots above the nodes of primary leaves wereremoved at various ages. The response of primary leaves to decapitationvaried according to their age. With age, they lost the abilityto increase their fresh weight, area, and chlorophyll contentbut not their DNA and RNA contents in response to decapitation.Decapitation stimulated chloroplast replication only withinthe period in which chloroplasts were replicating in controlleaves, but it induced chloroplast enlargement at any age. Therefore,the increase in DNA content after decapitation may be partiallydue to an increase in the amount of chloroplast DNA. When stems were heat-girdled above the nodes of the primaryleaves, these leaves showed responses similar to but smallerthan those to decapitation. The senescence of primary leavesseems to be controlled by the distribution of substances whichare transported from the roots.     

Effect of Benzyladenine on Diurnal Changes in DNA Content per Chloroplast and Chloroplast Replication in Intact Bean Leaves

The effect of benzyladenine (BA) on the diurnal changes in DNAand Chl contents per chloroplast and chloroplast replicationin primary leaves of bean plants (Phaseolus vulgaris L.) grownunder a 16 h light/8 h dark cycle was studied. Experiments weremade on primary leaves in the early expansion phase, where celldivision had been completed but chloroplasts were replicating.In untreated controls, chloroplast number, Chl content and freshweight per leaf showed daily periodic changes. Chl content perchloroplast increased in the light period every day, and freshweight per leaf increased most rapidly in the early dark period.Chloroplast number per leaf increased rapidly in the early darkperiod on day 9, though the increase began a little earlierand was less sharp on days 8 and 10. During these periods, DNAcontent per chloroplast was decreasing due to chloroplast divisionas chloroplast DNA (ctDNA) per leaf remained unchanged throughoutthe experimental period. BA induced increases in Chi contentper chloroplast, ctDNA content and fresh weight per leaf within6 h of its application, regardless of whether it was appliedat or 10 h after the beginning of the light period. Applicationof BA at 10 h in the light period shifted the start of chloroplastreplication by 6 h compared to that in untreated controls. However,when BA was applied at the beginning of illumination, the startof chloroplast replication showed the same relative change intime as above. 5-Fluorodeoxyuridine (5-FdU) promptly preventedBA-induced increase in Chl content and chloroplast number perleaf as well as ctDNA content per leaf.     

Benzyladenine-Enhanced Cell Proliferation and -Suppressed Greening in Attached Young Bean Leaves

Changes in fresh weight, cell number, cell size and cell constituentswere studied during the growth of attached young bean (Phaseolusvulgaris L.) leaves after benzyladenine (BA) treatment. BA broughtabout the increase in DNA, RNA and protein contents and freshweight as well as the temporary inhibition of chlorophyll accumulationin growing leaves. After a lag period for about 12 hr, BA stimulatedcell division but not cell expansion. An increase in RNA contentoccurred during the lag period of BAinduced cell division growth. (Received November 5, 1980; Accepted March 10, 1981)     

Differential effects of benzyladenine and potassium on DNA, RNA, protein and chlorophyll contents and on expansion growth of detached cucumber cotyledons in the dark and light

Benzyladenine (BA) and KCl were applied to detached cucumber ( Cucumis sativus L. cv. Ohio) cotyledons in continuous light or in the dark with subsequent light. BA brought about an increase in fresh weight and in DNA, RNA and carotenoid contents in both treatments. KCl did not cause an increase in fresh weight and cellular constituents in the dark, but it did result in an increased fresh weight and DNA content after illumination or in continuous light. BA + KCl treatment resulted in increased carotenoid and DNA contents in the dark, and in increases in fresh weight and all cellular constituents upon subsequent exposure to light. The effects of BA and BA + KCl on growth and chlorophyll synthesis decreased with cotyledon age.
BA pretreatment in the dark eliminated the lag phase in chlorophyll synthesis and increased the rate of synthesis. Treatment in continuous light had little effect. KCl did not shorten the lag phase in chlorophyll synthesis, but it stimulated the rate of synthesis in the light. Dark pretreatment with BA + KCl markedly increased the effect of BA on chlorophyll synthesis. Chlorophyll content and fresh weight were higher in cotyledons treated with BA followed by KCl than in cotyledons treated in the reverse order. These results suggest that growth and greening in cucumber cotyledons are primarily controlled by BA and that KCl intensifies the BA effect after irradiation.     

The Effect of Benzyladenine on Changes in Nuclease and Protease Activities in Intact Bean Leaves during Ageing

Primary leaves of intact bean plants (Phaseolus vulgaris L.) were treated with benzyladenine (BA) at different stages during growth. Changes in DNase, RNase, and proteas activities in the leaves were followed. Unlike the case of various excised tissues, cytokinin raised the activities of these hydrolases in intact bean leaves. Because BA elevated the levels of DNA, RNA, and protein in intact leaves, it may stimulate both synthesis and decomposition of these cellular constituents. The hydrolase activities showed differential responses to BA according to the age at which the leaf received the hormone treatment.     

PP333对离体苹果苗的生长及其生理的影响

在生根培养基中加入0.5或2.0PPm PP333, 明显地减少了苹果离体新梢的鲜重和干重、叶片鲜重和叶面积,增加了比叶重、根的鲜重和干重及根梢鲜重和干重比,并促进了根的形成。PP333对单位叶重量的叶绿素含量没有影响,而增加了单位叶面积的叶绿素含量。经PP333处理后,叶片中的淀粉含量、过氧化物酶活性、蛋白质和游离氨基酸的含量均明显高于对照,可溶性糖与对照差异不明显。     

缺氮和复氮对菘蓝幼苗生长及氮代谢的影响

对基质育苗后水培的菘蓝进行缺氮与复氮处理,分析其生长情况及氮代谢产物含量的变化,探讨缺氮和复氮对菘蓝幼苗生长及氮代谢的影响,以提高菘蓝产量和品质以及栽培过程中的氮素利用效率。结果显示:(1)正常供氮条件下,菘蓝幼苗的叶绿素含量、谷氨酰胺合成酶(GS)活性、硝态氮含量、靛玉红含量为最高,而其株高、主根直径、根的鲜重与干重、叶的鲜重与干重、根系活力均最小。(2)缺氮处理增加了菘蓝幼苗的主根直径和根干重,提高其根系活力和硝酸还原酶(NR)活性,促进游离氨基酸在叶中的积累;但降低了GS的活性,也降低了叶中硝态氮、可溶性蛋白、靛玉红及根中游离氨基酸的含量;缺氮对叶中靛蓝的含量无明显影响。(3)复氮处理增加了菘蓝幼苗的株高、主根长、根鲜重、叶鲜重、叶干重,提高了其根系活力,降低了NR和GS的活性;与对照相比,复氮降低了叶中硝态氮含量,提高了叶中可溶性蛋白、靛蓝及根中游离氨基酸的含量,但对叶中游离氨基酸和靛玉红含量影响较小。研究表明,缺氮后再复氮有利于菘蓝幼苗叶的生长,同时有利于增加其叶内靛蓝含量,从而提高其产量和品质。     

Effect of certain dicarboxylic acid monoesters on growth,chlorophyll content,chlorophyllase and peroxidase activities,and gas-exchange of young maize plants

The effect of some dicarboxylic acid monoesters on growth, chlorophyll content, chlorophyllase (EC 3.1.1.14), and total peroxidase (EC 1.11.1.7.) activities was examined in detached and intact leaves of maize (Zea mays) plants grown in a greenhouse. The -monomethyl ester of itaconic acid (MEIA) at 1250 ppm had no effect on growth. However, application of the monoethyl ester of succinic (MESA) and monoethyl ester of adipic (MEAdA) acids (1250 ppm) resulted in an increased leaf area, fresh and dry weight of leaves and stems. These compounds retarded chlorophyll degradation in both detached and intact leaves. Chlorophyllase activity of the control and treated leaves was measured and related to chlorophyll content. Delaying of senescence by treatment with monoesters resulted in greater chlorophyll and protein content, compared with the control. However, the chlorophyllase activity/chlorophylla ratio in the treated plants decreased. Total peroxidase activity was higher in senescent leaves, but all treatments inhibited the increase of this enzyme activity. Prolonged carbon assimilative activity and enhanced leaf water use efficiency in treated plants was noted.     

Effects of Benzyladenine on Chlorophyll, DNA, RNA and Protein Content of Attached Young Bean (Phaseolus vulgaris L.) Leaves

N⁶-Benzyladenine (BA) was applied to intact bean (Phaseolusvulgaris L.) primary leaves at 2 and 6 days after imbibition,when they were in the cell division and post-cell division stages,respectively. BA treatment at day 2 temporarily inhibited an increase in chlorophyllcontent in the following day, but stimulated it in later days.No such inhibition by BA was observed for changes with timein DNA, RNA, and protein content and f. wt. On the other hand,BA treatment at day 6 enhanced RNA and protein content, withoutsignificant influence on DNA and chlorophyll content and f.wt. The mode of cytokinin action on greening in leaves during cell-divisiongrowth seems to be different from that in etiolated cotyledons. Phaseolus vulgaris L., bean, greening, benzyladenine, DNA, RNA, protein     

PP_(333)对离体苹果苗的生长及其生理的影响

在生根焙养基中加入0.5或2.0ppm PP_333,明显地减少了苹果离体新梢的鲜重和干重、叶片鲜重和叶面积,增加了比叶重、根的鲜重和干重及根梢鲜重和干重比,并促进了根的形成。PP_333对单位叶重量的叶绿素含最没有影响,而增加了单位叶面积的叶绿素含量。经PP_333处理后,叶片中的淀粉含量、过氧化物酶活性、蛋白质和游离氨基酸的含量均明显离于对照,可溶性糖与对照差异不明显。     

Adaptability ofMentha piperita l. to irradiance. Growth,specific leaf area and levels of chlorophyll,protein and mineral nutrients as affected by shading

Height growth ofMentha piperita L. is better at 44% than 100% daylight. At 14% daylight, growth is limited, probably by lack of photosynthate, and no flowering occurs. Specific leaf area and protein content increase significantly with the decrease of irradiance. Shade leaves contain more chlorophyll and potassium than sun leaves. Sun leaves show higher levels of calcium because of their more xeromorphic structure. Transfer experiments between light and shade indicate thatM. piperita responds very effectively to irradiance also in a late stage of the life cycle with changes of specific leaf area and chlorophyll content.     

Effects of Benzyladenine on Photosynthesis, Growth and Senescence of the Bean Plant

The net photosynthetic rate of attached primary bean leaves treated with benzyladenine (BA) decreased from 35 nano-grams carbon dioxide per square centimetre and second (ng cm^?2 s^?1) at week 2 to 17 ng cm^?2 s^?1 at week 4, and thereafter increased to 24 at week 6. By contrast the net photo-synthetic rate of the water-treated leaves decreased to 4–5 ng cm^?2 s^?1 at weeks 5 and 6. The stomatal resistance was not markedly affected by BA treatment. The BA-treated primary leaves had higher dry and specific weights, and the chlorophyll and carotenoid contents were greater than for the water controls. The pigment content of the BA-treated leaves steadily increased from week 2 to 6, whereas in the water controls it remained constant till week 4 and thereafter decreased. It is concluded that retardation of leaf senescence by BA is assoclatcd with a mnintenance of photosynthetic activity.     

Leaf Senescence: Correlated with Increased Levels of Membrane Permeability and Lipid Peroxidation, and Decreased Levels of Superoxide Dismutase and Catalase

The changes in membrane permeability (soluble leakage), lipidperoxidation, and activities of superoxide dismutase (SOD) andcatalase have been studied during in situ senescence of leavesof Nicotiana tabacum L., cv. Wisconsin 38. After full leaf expansionwas reached there was a rapid, almost linear increase in therate of ⁸⁶Rb leakage from the preloaded leaf discs, with leafage. Parallel with this increase in membrane permeability wasa cumulative increase in the level of lipid peroxidation. Atthe same leaf age there were changes in the activities of SODand catalase. SOD activity decreased on the basis of fresh weightbut did not change when measured on the basis of protein contentprobably due to relative stability of SOD during the senescence-associatedgeneral decline in protein content. Catalase activity firstincreased parallel with the chlorophyll content of the leafand then, after full leaf expansion, declined on the basis ofboth fresh weight and protein content. These changes in membranepermeability, lipid peroxidation, and the enzyme activitiescoincide in leaf age with the decline in protein and chlorophyllcontents and in chlorophyll a: b ratio. When the senescenceof the bottom-most leaves was reversed by removing the stemfrom immediately above them, the senescence-associated changesin protein and chlorophyll contents, lipid peroxidation, andthe enzyme activities were also reversed. It is suggested thatleaf senescence may be a consequence of cumulative membranedeterioration due to increasing level of lipid peroxidationprobably controlled by, among other factors, the activitiesof SOD and catalase.     

Retardation and Reversal of Senescence in Bean Leaves by Benzyladenine and Decapitation

During the early stages of growth when the primary leaves ofbeans (Phaseolus vulgaris L., cv. Kinghorn) are expanding, thereis an increase in chlorophylls, carotenoids and protein levelsas well as superoxide dismutase (SOD), catalase and peroxidaseactivities. However, following the initiation of flowering onday (d) 21 there is a steady decrease in all of these parametersexcept levels of peroxidase activity, and by d 35 the primaryleaves are also showing pronounced morphological symptoms ofsenescence. Following the onset of senescence, primary leaveswere also leaking and showed increased levels of malondialdehyde(MDA). In addition, there was an increase in the lipid phasetransition temperature of a membrane fraction consisting predominantlyof chloroplast membranes, which reflected the formation of gelphase lipid. By d 56, the leaves had abscinded. A single applicationof benzyladenine (BA) to the primary leaves or decapitationof the shoot above the primary leaf on d 9 retarded all of thesesenescence symptoms, with decapitation being more effectivethan BA. On d 35 when the primary leaves were pale green-yellow, a singleapplication of BA to the leaves or decapitation of the shootabove them reversed the symptoms of senescence. Decapitationwas more effective than BA as a means of reversal, causing chlorophyll,carotenoid and protein levels to rise to values higher thanthose present in the control leaves. Decapitation also reversedthe senescence-related changes in membrane phase properties,decreased membrane leakiness and reduced lipid peroxidation. (Received August 22, 1983; Accepted January 26, 1984)     

The influence of ancymidol on morphology,anatomy, and chlorophyll levels in developing and mature Helianthus annuus leaves

Ancymidol foliar spray at 132 mg·liter^–1 a.i. modified leaf anatomy of developing Helianthus annuus L. Mammoth Russian leaves, but not of mature leaves. Ancymidol was effective in retarding plant growth when applied at the young seedling or at a more mature stage of growth. Ancymidol increased leaf weight per unit area and chlorophyll content on an area and unit weight basis, regardless of stage of leaf development. Total chlorophyll per leaf was also increased in mature leaves. Thus, darker green foliage due to increased chlorophyll content and modified leaf anatomy responses were determined to be independent effects.Texas Agricultural Experiment Station paper no. 22927.     

Spatial patterning of pigmentation in evergreen leaves in response to freezing stress

Evergreen leaves of temperate climate plants are often subject to frosts. Changes in carbon gain patterns arise from freezing‐related tissue damage, and from interactions between light and temperature stress. We examined relationships between spatial patterns in freezing and concentrations of chlorophyll. Spatial patterns in pigmentation in leaves that had or had not been exposed to naturally occurring frosts were determined by conventional extraction techniques combined with high‐resolution hyperspectral imaging of reflectance from intact leaves. Predictive indices were developed to relate reflectance to chlorophyll content and chlorophyll a/b ratios within intact leaves. Leaves exposed to frosts had lower chlorophyll contents and more variable a/b ratios than protected leaves. In frost‐affected leaves, chlorophyll content was highest near leaf centres and decreased toward leaf tips and margins. Decline in chlorophyll content was associated with shifts in chlorophyll a/b ratios and increases in red pigmentation due to anthocyanin, with effects being greater on leaf sides exposed directly to the sun. These altered pigmentation patterns were consistent with patterns in freezing. The present results illustrate the fine scale of spatial variation in leaf response to freezing, and raise important questions about impacts of freezing on photosynthetic function in over‐wintering evergreens.     

Growth enhancement of soybean (Glycine max) upon exclusion of UV-B and UV-B/A components of solar radiation: characterization of photosynthetic parameters in leaves

Exclusion of UV (280–380 nm) radiation from the solar spectrum can be an important tool to assess the impact of ambient UV radiation on plant growth and performance of crop plants. The effect of exclusion of UV-B and UV-A from solar radiation on the growth and photosynthetic components in soybean (Glycine max) leaves were investigated. Exclusion of solar UV-B and UV-B/A radiation, enhanced the fresh weight, dry weight, leaf area as well as induced a dramatic increase in plant height, which reflected a net increase in biomass. Dry weight increase per unit leaf area was quite significant upon both UV-B and UV-B/A exclusion from the solar spectrum. However, no changes in chlorophyll a and b contents were observed by exclusion of solar UV radiation but the content of carotenoids was significantly (34–46%) lowered. Analysis of chlorophyll (Chl) fluorescence transient parameters of leaf segments suggested no change in the F _v/F _m value due to UV-B or UV-B/A exclusion. Only a small reduction in photo-oxidized signal I (P700⁺)/unit Chl was noted. Interestingly the total soluble protein content per unit leaf area increased by 18% in UV-B/A and 40% in UV-B excluded samples, suggesting a unique upregulation of biosynthesis and accumulation of biomass. Solar UV radiation thus seems to primarily affect the photomorphogenic regulatory system that leads to an enhanced growth of leaves and an enhanced rate of net photosynthesis in soybean, a crop plant of economic importance. The presence of ultra-violet components in sunlight seems to arrest carbon sequestration in plants. An erratum to this article can be found at     

Senescence of rice leaves IV. Influence of benzyladenine on chlorophyll degradation

Why benzyladenine (BA) retards chlorophyll degradation of riceleaf segments, but does not prevent it was investigated. WhenBA solutions bathing segments of rice leaves were replaced daily,the effect of BA was not enhanced. Solutions of BA kept at 27°Cin the dark for 4 days were as active as fresh solutions. Itseems unlikely, therefore, that the decrease in the chlorophyllcontent with increased incubation time in BA-treated leaf segmentsis caused by inactivation of BA either in the leaves or in solution.Of 25 L-amino acids at 50 mM added singly with BA, 19 were antagonisticto the effect of BA on chlorophyll content, but four, L-arginine,L-histidine, L-lysine and L-methionine, significantly enhancedthe effect of BA. The effects of amino acids decreased witha decrease in the amino acid concentration or an increase inBA concentration. When concentrations were decreased to 5 mM,only L-lysine slightly increased the chlorophyll content inBA-treated leaf segments. L-Proline and L-tryptophan did notmodify the effect of BA on chlorophyll content. Effects of aminoacids on chlorophyll content in leaf segments without BA treatmentare similar to those with BA. Furthermore, cycloheximide (50µg/ml), which decreased the soluble amino acid content,increased the chlorophyll content in BA-treated leaf segments. Since an accumulation of soluble amino acids precedes the degradationof chlorphyll in BA-treated leaf segments, probably antagonismscaused by the amino acids accumulated in the tissue, preventthe added BA from being fully effective in stopping chlorophyllloss. (Received June 2, 1980; )     

Senescence of rice leaves IV. Influence of benzyladenine on chlorophyll degradation

Why benzyladenine (BA) retards chlorophyll degradation of riceleaf segments, but does not prevent it was investigated. WhenBA solutions bathing segments of rice leaves were replaced daily,the effect of BA was not enhanced. Solutions of BA kept at 27°Cin the dark for 4 days were as active as fresh solutions. Itseems unlikely, therefore, that the decrease in the chlorophyllcontent with increased incubation time in BA-treated leaf segmentsis caused by inactivation of BA either in the leaves or in solution.Of 25 L-amino acids at 50 mM added singly with BA, 19 were antagonisticto the effect of BA on chlorophyll content, but four, L-arginine,L-histidine, L-lysine and L-methionine, significantly enhancedthe effect of BA. The effects of amino acids decreased witha decrease in the amino acid concentration or an increase inBA concentration. When concentrations were decreased to 5 mM,only L-lysine slightly increased the chlorophyll content inBA-treated leaf segments. L-Proline and L-tryptophan did notmodify the effect of BA on chlorophyll content. Effects of aminoacids on chlorophyll content in leaf segments without BA treatmentare similar to those with BA. Furthermore, cycloheximide (50µg/ml), which decreased the soluble amino acid content,increased the chlorophyll content in BA-treated leaf segments. Since an accumulation of soluble amino acids precedes the degradationof chlorphyll in BA-treated leaf segments, probably antagonismscaused by the amino acids accumulated in the tissue, preventthe added BA from being fully effective in stopping chlorophyllloss. (Received June 2, 1980; )