Abnormal Stomatal Behaviour and Leaf Anatomy in Capsicum annuum, scabrous diminutive, a Wilty Mutant of Pepper

An attempt is made to explain the tendency to excessive wiltingin scabrous diminutive, a pepper mutant. For this, mutant andnormal plants were compared with respect to leaf anatomy, transpirationof whole plants and detached drying leaves, density and openingof stomata, staining of potassium in epidermal cells and rootpressure. A much greater proportion of intracellular space was found inthe mutant leaf which contains fewer and smaller mesophyll cellsthan the normal plant. The anticlinal walls of the epidermisof the mutant leaf were almost straight whereas those of thenormal were wavy. Transpiration per unit leaf area of wholeplants, percentage of stomata open both day and night, and waterloss from detached drying leaves were all higher in the mutant.Potassium staining in guard cells was similar in both planttypes, slightly less in darkness and marginally higher in light.The subsidiary cells of normal leaves did not stain at all,but those of the mutant leaves stained heavily in both lightand darkness. Root pressure was lower in the mutant. Possible explanations for the tendency of the pepper mutantto wilt are discussed.     

Stomatal Behaviour and Water Relations of Chilled Phaseolus vulgaris L. and Pisum sativum L.

Leaf diffusion resistance interpreted as stomatal resistance,leaf water potential (_w), solute potential (_s) and leaf turgorpotential (_p) of the chilling sensitive species Phaseolus vulgariswere determined during chilling at 4 °C in the light. Bothchill-hardened and non-hardened plants were used. For comparison,the chilling resistant species Pisum sativum was also used. The results for chilled P. sativum were similar to those obtainedfor chill-hardened P. vulgaris plants receiving a chilling treatment.In both cases a reduction in stomatal aperture and the maintenanceof a positive leaf turgor were the responses to chilling. Leavesof chilled but non-hardened P. vulgaris plants were found tomaintain open stomata throughout the chilling treatment despitea severe wilt developing after 7 h at 4 °C. This was incontrast to the chill-resistant P. sativum. which showed a rapidclosing and subsequent re-opening of the stomata to a new reducedaperture. During the first 12 h of chilling _wof P. vulgaris leaves changedfrom –0.47 MPa to –1.24 MPa. On more prolonged chilling_w tended to return to pre-chilling values. In addition. _p decreasedfrom 0.42 MPa to zero after only 9 h of chilling, and remainedat this value for the remainder of the chilling period, _s, changedrapidly from –0.89 MPa to –1.35 MPa in the first7.5 h, and after 9 h. _w and _s, were equal, i.e. zero _p. In contrast,the chilling resistant plant P. sativum maintained a positive_p throughout the chilling period, and there was little differencebetween values of _w, and _s in control and chilled leaves. Key words: Chilling, Stomata, ater relations, Phaseolus vulgaris, Pisum sativum     

Development of the alt Mutant of Pisum sativum L

The alt (albina-terminalis) mutant of Pisum sativum L. germinates normally, produces several nodes, and then above a sharp transition produces 2 to 3 bleached nodes, ceases growth, and eventually dies. Green nodes have normal chlorophyll content, absorption spectra, photosynthetic rates, and ultrastructure. In bleaching tissues, the chloroplasts degenerate rapidly, followed by extensive disruption and loss of the remaining cytoplasm and organelles. Application of tissue extracts of normal genotypes of pea, corn, and bean stimulates apical development of alt. The resulting tissues have essentially normal structure and function. Application of thiamine, thiamine monophosphate, and thiamine pyrophosphate also stimulate normal apical development at concentrations of 1 micromolar and above. Partial characterization of the stimulus from pea seed extracts is consistent with thiamine as the active factor.     

An Investigation into the Rate and Control of Assimilate Movement from Leaves in Pisum sativum

Export studies were made on leaves of Pisum by monitoring the¹⁴CO₂-treated source leaf at its surface at frequent intervals.Radiocarbon levels of fresh leaf samples showed a good correlationwith results from the more conventional methods of radiocarbonestimation which involve destructive analysis. The rate of export was highest in plants which had been defoliated,except for the source leaf 20 h or more before the start ofthe export study. Removal of the shoot apex reduced export andprogressive reduction in sink capacity was associated with decreasedexport rates, particularly over short time periods. Export rateswere similar in defoliated and non-defoliated plants where theshoot apex and the roots had been excised. This suggested thata decrease in the source resulted in higher export rates fromthe remaining source only when active sinks were present; thisin turn suggests that, at least under these conditions, activeremoval of photosynthate is more important in controlling exportthan the photosynthate build-up in the leaf itself. The non-destructive technique enabled comparisons to be madebetween export curves for individual plants. It was found thatin experiments replicated in time, the same relationship betweentreatments was present on different days and the shape of theexport curves was similar but the absolute values for exportedradiocarbon sometimes varied considerably.     

Abnormal Stomatal Behaviour and Hormonal Imbalance in flacca, a Wilty Mutant of Tomato: EFFECT OF ABSCISIC ACID AND AUXIN ON STOMATAL BEHAVIOUR AND PEROXIDASE ACTIVITY

The wilty tomato mutant flacca and the normal variety RheinlandsRuhm were compared in terms of: (1) potassium transport intoand out of the guard cells, (2) cell wall properties which includeprotein, hydroxyproline and peroxidase activity, and (3) activityof indol-3yl-acetic acid oxidase. Also studied were the effectsof auxin on stomatal behaviour and peroxidase activity whenapplied to normal plants during development, and the short-termeffect of abscisic acid on the resistance of flacca stomatato closure under plasmolysis. Potassium transport, wall protein and hydroxyproline all seemedto be equal in mutant and normal plants. Peroxidase activitywas higher in the soluble and wall fractions of the mutant,and decreased toward normal in the mutant treated with abscisicacid. More stomata were open and peroxidase activity was higherin normal plants treated with auxin during development. Thepercentage of open stomata under plasmolysis was lower and theiraperture size was smaller in the epidermal strips taken fromabscisic-acid-treated mutant plants than from control mutantplants.     

Effects of SO(2) on Stomatal Metabolism in Pisum sativum L

Pea (Pisum sativum L. cv `Little Marvel') plants were exposed to SO₂ for short term (3 hours) and long term (2 days) at 0.2 and at 0.5 microliter per liter (ppm) levels. The effect of this treatment on the activity of phosphoenolpyruvate carboxylase, NAD- and NADP-malate dehydrogenases, and alanine aminotransferase from epidermis and whole leaves was investigated. Short-term exposure to SO₂ at 0.2 or 0.5 ppm decreased the activity of the carboxylase and the dehydrogenases in the epidermis. In contrast, the activity of the same three enzymes increased in whole leaves with either short- or long-term exposure to SO₂. Alanine aminotransferase in epidermis or whole leaves was not much affected by short-term exposure, but the epidermal activity was decreased and whole leaf activity was increased with long-term exposure. SO₂ exposure which was initiated prior to illumination decreased the free thiol content of both epidermis and of whole leaf. Net photosynthesis was reversibly inhibited by long-term exposure to SO₂ at 0.5 ppm. No effect of 0.5 ppm SO₂ on stomatal conductance was detectable after 3 hours. Stomatal conductance appeared to decrease after longer exposure times (2 days) at 0.5 ppm.     

Sink to Source Transition in Tendrils of a Semileafless Mutant, Pisum sativum cv Curly

Sink to source transition parallels loss of thigmotropic capacity in tendrils of a semileafless mutant, Pisum sativum cv Curly. Macroscopic tendril development is subdivided based on thigmotropic capacity. Stage I is the elongation stage and, although the rate of photosynthesis is similar to that of stage II and III tendrils, dark respiration rates are higher in stage I. During stage II, tendrils are thigmotropic and act as a sink. Even though stage II tendrils have CO₂ exchange characteristics similar to those of stage III tendrils, which are coiled, our fluorescein, ¹⁴C-partitioning, and ¹¹C-translocation experiments suggest that stage I and II tendrils do not export carbon. Only stage III tendrils act as sources of newly fixed carbon. Export from them is blocked by cold, heat girdling of the petiole, or anoxia treatment of the tendrils. A late stage II tendril complex, in which coiling is occurring, may be exporting photoassimilates; however, this phenomenon can be attributed to the fact that the pea leaf is a compound structure and there may be one or more stage III tendrils, no longer thigmotropic, within the tendril complex. Photosynthetic maturity in pea tendrils occurs at stage III and is characterized by the ability of these tendrils to export photoassimilates.     

Carbon Dioxide Photoassimilation in Normal-leaved and Mutant Forms of Pisum sativum L.

The reproducible steady-state carbon dioxide (CO₂) photoassimilationpotentials of three mutants and a normal form of pea (Pisumsativum L.) have been compared. The three mutants studied differed markedly in foliar morphology:genotype af af Tl Tl had leaflets converted to tendrils; AfAf tl tl had tendrils converted to leaflets; af af tl tl hadrelatively minute leaflets on a branched petiole. Interest layprimarily in the phenotype with only tendrils since it provideda potential means of reducing the volume of haulm that has tobe rapidly processed in the case of vining peas, and dried inthe case of harvest peas. These mutants had been derived from relatively unimproved cultivars.Before completion of the lengthy backcrossing required to makea full assessment of the value of such mutants an interim studyusing infra red gas analysis indicated that, in terms of CO₂ photoassimilation perunit area of youngest expanded attached leaf of glasshouse-grownplants, the mutants were comparable to normal. The phenotypewith only tendrils was the least efficient of those assayedat utilizing light of an intensity below 100 J m² sec¹ (400–700nm), and on a unit dry-weight basis it was only 18 per centas efficient as a normal-leaved pea. The other mutants werecomparable to normal in this respect. Comparison of CO₂ photoassimilation of glasshouse-grown andfield-grown plants showed them to be similar though they differedin dry weight, transpiration, and dark respiration.     

Mutant aminopeptidases of Pisum sativum. I. Developmental genetics and chemical characteristics

Summary Two forms of aminopeptidase (AmP) were found, by conventional zone electrophoresis, to be present in all tissues at various stages of normal development and differentiation of Pisum sativum. One of the enzymes (AmP-1) proved to be polymorphic, with alternate electrophoretic forms existing in different inbred pea strains, while the other enzyme (AmP-2) was found to be monomorphic. The AmP-1 variants are under the control of two codominant alleles (AmP-1 ^F and AmP-1 ^S) at the AmP-1 locus. The AmP-2 enzyme is most likely controlled by a separate genetic locus. Substrate specificity studies, using various -amino acid naphthylamides as substrates, showed that the aminopeptidases of Pisum are not specific for leucine N-terminal residues. The AmP-1 and AmP-2 enzymes behaved quite differently with respect to substrate specificity and metal ion inhibition, suggesting differences in the biological function and relatedness of the two enzymes.This investigation was supported by the U.S. Atomic Energy Commission under Contract No. AT(11-1)1338.     

Abnormal Stomatal Behavior and Hormonal Imbalance in flacca, a Wilty Mutant of Tomato: II. Auxin- and Abscisic Acid-like Activity

The wilty tomato mutant, flacca, and the control variety, Rheinlands Ruhm, were compared with regard to the endogenous activity and concentration of auxin- and abscisic acid-like substances during ontogeny. The mutant wilts fast under water deficit because of inability to close its stomata. Symptoms characteristic of excessive auxin are evident in the developing mutant. Among these symptoms are branch and leaf epinasty, excessive rooting along the stem, and increased apical dominance. By using a leucine-incorporation assay, spray of whole plants with 2,4-dichlorophenoxyacetic acid, and wheat coleoptile bioassay, indications were found of an excess of activity and concentration of auxin-like substances in shoots of young and mature mutant plants. The wheat coleoptile bioassay also revealed a much lower amount of substances with abscisic acid-like activity in the mutant compared with the normal plant. In contrast to the appearance during ontogeny of morphological symptoms characteristic of auxin excess in the mutant, the absolute amount of auxin-like substances and their activity in incorporation of leucine decreased with age. A parallel decrease of the concentration and activity of auxin-like compounds was also found in the normal plant. The concentration of abscisic acid-like substances increased with age in both genotypes. The disagreement between the increasing morphological symptoms and the decrease of auxin-like activity and concentration is discussed, together with the possibility of a causal relationship between auxin-and abscisic acid-like activity and stomatal behavior.     

Abnormal Stomatal Behavior and Hormonal Imbalance in flacca, a Wilty Mutant of Tomato: I. Root Effect and Kinetin-like Activity

The wilty tomato mutant, flacca, and the normal variety, Rheinlands Ruhm, were compared for kinetin-like activity in ontogeny. The mutant wilts easily because its stomata resist closure. This stomatal resistance decreases with age. The occurrence of a root factor which induces stomatal opening was inferred from grafting experiments. It was hypothesized that the excessive stomatal openings in the mutant may result from excess of kinetin-like activity in the leaf of that plant. In addition, it was suggested that the closure of stomata in the aging mutant is due to a decrease of kinetin-like activity with age. Kinetin-like activity in the leaf was determined by incorporation of labeled leucine. The concentration of cytokinins in root exudate and leaf extract was determined by the soybean callus assay. Evidence was presented of higher kinetin-like activity in the leaves of the mutant and higher cytokinin concentration in its root exudate. Cytokinin concentration in the shoot was found to be only slightly higher in the mutant than in the normal plants. Kinetin-like activity in the leaf and cytokinin concentration of root exudate decreased with age in both mutant and normal plants. Kinetin-like activity in the leaves of mutant plants, which phenocopy the normal variety as a result of continuous application of abscisic acid, was lower than in control mutant plants. The significance of these findings per se and in connection with stomatal behavior is discussed.     

An Endogenous Suppressor of the Defense Response in Pisum sativum

Healthy pea plants contain a substance, tentatively called "endogenoussuppressor", which specifically suppresses the accumulationof pisatin in pea plants that is induced by treatment with CuCl₂or an elicitor from Mycosphaerella pinodes. This suppressorelicits the accumulation of phytoalexins in other legumes, suchas kidney bean, soybean and cowpea. The endogenous suppressorfunctions to delay the accumulation of pisatin, the activationof phenylalanine ammonialyase (PAL) and the accumulation ofmRNAs for PAL and chalcone synthase induced by the elicitorfrom M. pinodes. The substance specifically induces susceptibilityto nonpathogens, such as Mycosphaerella ligulicola and M. melonis,in pea out of four species of legume tested, but the effectis not cultivar-specific. Thus, the endogenous suppressor inhealthy pea plants suppresses a series of self-defense reactionsand induces susceptibility in pea plants in a species-specificmanner, being similar to the exogenous fungal suppressor fromthe pea pathogen, M.pinodes. (Received February 19, 1992; Accepted May 11, 1992)     

A Comparison between Geotropism and Geoelectric Effect in Pisum sativum and Its Mutant ageotropum

The auxin concentration in roots of Pisum sativum ageotropum was examined by three indirect methods:

• 1) Supply of auxin before geotropic stimulation;
• 2) Lateral placing of the root tip;
• 3) Inhibiting the auxin transport in half of the root.

All the results indicated supraoptimal auxin concentration. When decapitated ageotropum roots were supplied with 1.5 mm long tips from normal Pisum roots their geotropic reactivity was almost restored. The geoelectric potential of stems of Pisum sativum and its mutant ageotropum was measured. In ageotropum stems the geoelectric potential was less and the geotropic reaction appeared later than in the normal stems.     

The Isoperoxidases of Pisum sativum

The heterogeneity of the peroxidases in peas was examined by starch gel electrophoresis. Comparisons were made between tall and dwarf cultivars and among organ systems developed in light and darkness. Isoperoxidase bands could be grouped as cathodic, anodic and near-neutral (at pH 9.0) types. The cathodic set stained well with guaiacol oxidation products whereas some anodic bands reacted preferentially with 2,6-dimethoxyphenol. Some near-neutral bands were aceto-carmine positive and may have been organellar.Each organ had a characteristic isozyme pattern, and the band patterns in corresponding organs from different varieties were far more alike than were the patterns in the different organs within each variety. Ontogenetic changes were marked in all 3 organ systems, principally in the cathodic bands. The effect of light on isozymal patterns was quantitative rather than qualitative, possibly influencing the isoperoxidases secondarily via its effect upon organ physiology and development.     

An Analysis of Seed Development in Pisum sativum L.

Growth analysis has been performed on developing seeds and seedcomponents of six contrasting genotypes of Pisum sativum. Seeddevelopment has been divided into three phases of high growthrate separated by two ‘lag’ phases, or phases oflow growth rate. It is suggested that the timing of these growthphases may not be determined by the developing seed, since thereappeared to be no consistent correlation with particular physiologicalstages of seed development. The relationship between the absolutegrowth rate of the embryo sac and of the embryo as determinedfrom changes in volume is reflected in the accumulation andabsorption of the endosperm. The relative growth rate of theembryo volume was invariably higher than that of the embryosac although the difference between these two relative ratesvaried with genotype and may account in part for the differencein seed phenotype. It is suggested that the testa and embryo are sinks which bothcompete for the endosperm which may act as a common source,and that this relationship accounts for variation in endospermvolume. It is concluded that seed development is dependent on threelevels of plant organization, the maternal parent, interactionsbetween the components of the seed and the genetic constitutionof the embryo. Pisum sativum L., garden pea, seed development, growth analysis     

An Acidic Polysaccharide in Seeds of Pisum sativum L.

A phenanthrene-assimilating bacterium which belongs to the genus Aeromonas was isolated from soil. The cells which adapted to phenanthrene required a growth lag time on a naphthalene medium. The cells oxidized l-hydroxy-2-naphthoate (1H2NA), 2-carboxybenzaldehyde (2CBAL), o-phthalate (OPA) and protocatechuate (PCA) but did not oxidize salicylaldehyde (SAL), salicylate (SA) and catechol (CAT) which are intermediates in naphthalene catabolism. Using the cell-free extract, the same results were obtained in oxidative capacity. The intact cells metabolized 1H2NA and 2CBAL without the lag time, giving 2CBAL and PCA, respectively. The ammonium sulfate-treated extract prepared from the cells grown in phenanthrene medium, converted 1H2NA to 2CBAL and 2CBAL to OPA. It was suggested that the Aeromonas sp. degraded phenanthrene through OPA.