Abscisic acid (ABA) is required for the regulation of seed maturation in maize (Zea mays L.). Mutants blocked in ABA synthesis (such as viviparous-5) do not mature to quiescent, desiccation-tolerant seeds, but germinate on the ear midway through kernel development. Because gibberellins (GA) and ABA act antagonistically in many aspects of plant development, we hypothesized that ABA antagonizes a positive GA signal for precocious germination in maize. In these experiments, we show that a GA deficiency early in seed development, induced genetically or via biosynthesis inhibitors, suppresses vivipary in ABA-deficient developing kernels. The resulting seeds have both desiccation tolerance and storage longevity. Temporal analysis of GA accumulation in wild-type kernels revealed the accumulation of bioactive GA(1) and GA(3) prior to the peak in ABA content. We speculate that these GAs stimulate a developmental program leading to vivipary in the absence of normal amounts of ABA, and that a reduction of GA content re-establishes an ABA/GA ratio appropriate for suppression of germination and induction of maturation. In contrast, the induction of a GA deficiency did not suppress vivipary in viviparous-1 mutant kernels, suggesting that VP1 acts downstream of both GA and ABA in programming seed development.

Pea weevil (Bruchus pisorum L.) oviposition on pods of specific genetic lines of pea (Pisum sativum L.) stimulates cell division at the sites of egg attachment. As a result, tumor-like growths of undifferentiated cells (neoplasms) develop beneath the egg. These neoplasms impede larval entry into the pod. This unique form of induced resistance is conditioned by the Np allele and mediated by a recently discovered class of natural products that we have identified from both cowpea weevil (Callosobruchus maculatus F.) and pea weevil. These compounds, which we refer to as "bruchins," are long-chain alpha,omega-diols, esterified at one or both oxygens with 3-hydroxypropanoic acid. Bruchins are potent plant regulators, with application of as little as 1 fmol (0.5 pg) causing neoplastic growth on pods of all of the pea lines tested. The bruchins are, to our knowledge, the first natural products discovered with the ability to induce neoplasm formation when applied to intact plants.

The amount of active gibberellin (GA) in plant tissues is determined in part by its rate of catabolism through oxidation at C-2. In pea (Pisum sativum L.) seeds, GA 2-oxidation is controlled by the SLN (SLENDER) gene, a mutation of which produces seedlings characterized by a slender or hyper-elongated phenotype. We cloned a GA 2-oxidase cDNA from immature pea seeds by screening an expression library for enzyme activity. The clone contained a full-length open reading frame encoding a protein of 327 amino acids. Lysate of bacterial cultures expressing the protein converted the C(19)-GAs, GA(1), GA(4), GA(9), and GA(20) to the corresponding 2beta-hydroxy products. GA(9) and GA(20) were also converted to GA(51) and GA(29) catabolites, respectively. The gene appeared to be one member of a small family of GA 2-oxidases in pea. Transcript was found predominantly in roots, flowers, young fruits, and testae of seeds. The corresponding transcript from sln pea contained a point mutation and did not produce active enzyme when expressed heterologously. RFLP analysis of a seedling population segregating for SLN and sln alleles showed the homozygous mutant allele co-segregating with the characteristic slender phenotype. We conclude that SLN encodes GA 2-oxidase.

In his studies on the nature of inheritance, Gregor[Mendel (1866)][1] examined seven pairs of traits in pea, including one he called “difference in the length of the stem” (Fig. [1][2]). The tall character dominated the dwarf, segregating three tall to one dwarf. When Mendel's work was

The major gibberellin (GA) controlling stem elongation in pea (Pisum sativum L.) is GA1, which is formed from GA20 by 3beta-hydroxylation. This step, which limits GA1 biosynthesis in pea, is controlled by the Le locus, one of the original Mendelian loci. Mutations in this locus result in dwarfism. We have isolated cDNAs encoding a GA 3beta-hydroxylase from lines of pea carrying the Le, le, le-3, and led alleles. The cDNA sequences from le and le-3 each contain a base substitution resulting in single amino acid changes relative to the sequence from Le. The cDNA sequence from led, a mutant derived from an le line, contains both the le "mutation" and a single-base deletion, which causes a shift in reading frame and presumably a null mutation. cDNAs from each line were expressed in Escherichia coli. The expression product for the clone from Le converted GA9 to GA4, and GA20 to GA1, with Km values of 1.5 microM and 13 microM, respectively. The amino acid substitution in the clone from le increased Km for GA9 100-fold and reduced conversion of GA20 to almost nil. Expression products from le and le-3 possessed similar levels of 3beta-hydroxylase activity, and the expression product from led was inactive. Our results suggest that the 3beta-hydroxylase cDNA is encoded by Le. Le transcript is expressed in roots, shoots, and cotyledons of germinating pea seedlings, in internodes and leaves of established seedlings, and in developing seeds.

Effects of the Na and Le loci on gibberellin (GA) content and transport in pea (Pisum sativum L.) shoots were studied. GA(1), GA(8), GA(17), GA(19), GA(20), GA(29), GA(44), GA(8) catabolite, and GA(29) catabolite were identified by full-scan gas chromatography-mass spectrometry in extracts of expanding and fully expanded tissues of line C79-338 (Na Le). Quantification of GAs by gas chromatography-single-ion monitoring using deuterated internal standards in lines differing at the Na and Le alleles showed that na reduced the contents of GA(19), GA(20), and GA(29) on average to <3% and of GA(1) and GA(8) to <30% of those in corresponding Na lines. In expanding tissues from Na le lines, GA(1) and GA(8) concentrations were reduced to approximately 10 and 2%, respectively, and GA(29) content increased 2- to 3-fold compared with those in Na Le plants. There was a close correlation between stem length and the concentrations of GA(1) or GA(8) in shoot apices in all six genotypes investigated. In na/Na grafts, internode length and GA(1) concentration of nana scions were normalized, the GA(20) content increased slightly, but GA(19) levels were unaffected. Movement of labeled GAs applied to leaves on Na rootstocks indicated that GA(19) was transported poorly to apices of na scions compared with GA(20) and GA(1). Our evidence suggests that GA(20) is the major transported GA in peas.

Abstract Several techniques were tested to improve the development of Colorado blue spruce ( Picea pungens Engelm. ‘Hoopsi’) grafts. In the Pacific Northwest, Picea grafts are normally made on active rootstocks in heated greenhouses between December and mid-March. Grafting on dormant rootstocks and holding these grafts in an unheated, polyethylene-covered lath house resulted in generally higher graft success. IBA, NAA, and BA applied to the base of the scion just before grafting increased graft success by 10% to 13%. Retarding the development of the rootstock by dikegulac applications or by bud removal stimulated scion growth. Polyethylene tents and a film-forming anti-transpirant had no effect on graft success. Chemical names used N- (phenylmethyl)-1 H -purin-6-amine (BA); 2,3:4,6- bis -0-(l-methylethylidone)-a-l- xylo -2-hexulofuranosonic acid (dikegulac); 1 H- indole-3-butyric acid (IBA); 1-naphthaleneacetic acid (NAA).

Abstract The study evaluated the roles of storage carbohydrates and neutral lipids in the success of Colorado blue spruce ( Picea pungens Englemann ‘Hoopsi’) grafts. These scions do not require photosynthesis nor receive photosynthates from the rootstock during union development. Carbohydrate and neutral lipid contents, along with respiration and scion water relations, were measured during union development. Stored carbon compounds were sufficient to supply the needs of the scion during the 9 weeks of union development. Estimates of carbohydrate use indicated that decreases in sugar content (bark and needle) were insufficient to account for more than 25% of the estimated respiration. The results indicate that the quantity of carbon storage compounds is not a factor in graft success. We propose that neutral lipids may be the major carbon reserve of the scion during graft formation.

Needle starch metabolism was studied during graft development of Colorado blue spruce (Picea pungens Englemann ‘Hoopsi’) scions on Norway spruce [Picea abies (L.) Karst] rootstocks. Starch accumulated during the initial stages of union formation, but the rate of accumulation slowed over time. Peak starch content in developing greenhouse grafts was ≈30% and, in lath house grafts, ≈50% of that in 3-year-old grafts forced in the greenhouse. Prior to budbreak, starch content declined rapidly, stabilizing at pre-grafting levels during shoot elongation. Grafts with misaligned unions accumulated starch during the first week, but the starch content then declined. Preventing photosynthesis in scions during union formation prevented starch accumulation, but did not affect graft success or subsequent scion growth. We concluded that neither starch accumulation nor current photosynthesis in the scion were required during union development.

The role of scion water relations was studied using Colorado blue spruce ( Picea pungens Engelmann ‘Hoopsi’) scions on Norway spruce [ Picea abies (L.) Karst.] rootstocks grown either in a greenhouse or in a covered, unheated lath house. In greenhouse-grown grafts, total water potential (ψ T ) and relative water content (RWC) of the scions declined rapidly the first 2 weeks. Thereafter, both ψ T and RWC were maintained or gradually increased in successful grafts. With scion budbreak, ψ T rapidly increased to −1.0 MPa. This increase occurred 1 to 2 weeks after tracheid connections matured, based on dye movement through the graft union. At the same time, the ψ T and RWC of unsuccessful grafts declined rapidly. Osmotic potentials (ψ w ) increased 3 weeks prior to budbreak in successful grafts. However, ψ π declined in unsuccessful grafts more rapidly than ψ T , resulting in increased calculated turgor pressures with graft failure. Lath house-grown grafts had higher scion ψ T and higher graft success than those in the greenhouse, but required more time for union development. Based on this data and previous work, an hypothesis relating changes in ψ T , maturation of connecting tracheids, and scion budbreak to graft success or failure is presented.

Total water and osmotic potential, turgor pressure and transpiration rate were measured on scions of Picea pungens (Englemann) during union development. In controlled environments, declines in water potential were correlated with lower transpiration rates to about −2.0 MPa. Water potentials below −2.0 MPa resulted in graft failure and were associated with sharply increased transpiration rates. Bulk turgor pressures remained high in the needles during this period of declining water potential and increasing transpiration. Transpiration rates of successful and unsuccessful greenhouse grafts were not significantly different during union development. Transpiration rates of these grafts were highest around dawn, then declined throughout the day only to increase again after sunset. High bulk needle turgor values (1.3 MPa), maintained by osmotic adjustment, may prevent stomatal closure of Picea scions at water potentials below −2.0 MPa.

Rootstocks (Piceaabies (L.) Karst.) and scions (Piceapungens Engelm.) were labelled separately during graft union development with 14CO2 and translocation of the labelled photosynthate determined qualitatively and quantitatively. Rootstock photosynthates did not cross the graft union after scion budbreak had started. Total recovery of labelled scion photosynthates in scions declined from nearly 60% to less than 10% during the 1st week after grafting, and did not increase until xylem connections were established 1-2 weeks before budbreak. Less than 2% of the recovery from the scion was found in the graft union before scion budbreak. Most of the label recovered before scion budbreak was in the needle sugar fraction. After budbreak, most of the label was recovered in elongating buds.

Abstract— June yellows (J‐y) of strawberry (Fragaria) is an inheritable condition for which no causal pathogen has been demonstrated. Spectroscopic analysis of intact leaf lamina was applied to strawberry leaves with J‐y. The spectra were analyzed by fourth derivative technique. Differences were found between asymptomatic and affected leaves with respect to chlorophyll‐protein complexes. Affected leaves show spectra consistent with loss of certain chlorophyll‐a‐proteins (Ca). Distinct types of effects are found. In one type Ca 684 decreases, in another Ca 693 is diminished. Studies of strawberry clone pedigree suggest that Ca 684 losses are observed in clones with Howard 17 parentage, and Ca 693 losses in clones with Aberdeen parentage. One clone with both Howard 17 and Aberdeen parentage had a spectra consistent with diminished Ca 684 and Ca 693. The simplest explanation of the data is that J‐y results from several different types of genetic lesions on different Ca. Some viral infection effects on Ca spectra are also described.

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.

Abstract Various storage treatments were imposed on cut douglas-fir Christmas trees to measure drying relative to the damage threshold ψ of −3.5 MPa. In a greenhouse (day/night 16°/10° ± 5°C, RH 70-95%), cut douglas-fir dried to −3.5 MPa in 4 days. Overhead irrigation under these conditions maintained ψ about − 3.2 MPa for 9 days. Outdoors (day/night 672° ±9°), ψ declined to a range of −2.5 to −3.0 MPa depending on the weather. Overhead irrigation outdoors maintained ψ between −1.0 to −2.5 MPa. The antitranspirants tested did not reduce the rate of water loss significantly in the greenhouse. Outdoors, ψ of Vapor Gard-treated trees was similar to the irrigated trees, but Vapor Gard caused serious cosmetic defects. None of the other antitranspirants tested reduced moisture loss outdoors.

A method for direct estimation of percentage apoplastic water volume (% APO) in conifer needles is described. The method presented here, and designated the pressure‐needle (P‐N) method, measures the relative water content of the needles to develop a curve similar to the pressure‐volume (P‐V) curve. P‐V and P‐N curves were developed for Picea pungens Engelm. cv. Hoopsi, Pinus sylvestris L., Abies gradis (Dougl.) L., and Pseudotsuga menziesii (Mirb) Franco. The % APO estimated by the two procedures varied as much as 2‐fold, while other parameters were similar. The P‐V method generated consistently higher and more variable % APO than the P‐N method, due to the inclusion of the apoplastic water of the stem in the P‐V method. For conifers, the P‐N method offers a more accurate and precise method for determining % APO.

Cut coastal Douglas-fir trees (1.0 to 1.5 m) were allowed to dry to various water potentials in a greenhouse. About one-half of the tree population, dried to a water potential (ψ) of −3.5 MPa, lost significant quantities of needles but were otherwise comparable to undried trees. Drying to −4.0 MPa or below resulted in significantly reduced water uptake after rehydration and irreversible damage. Changes in percentage of moisture content and stomatal conductance generally paralleled ψ but were less useful indices of the damage threshold. Bark wrinkling and percentage of broken needles were useful morphological indices of the damage threshold. Subjective ratings of quality were less reliable indices of the damage threshold. Water potential was an appropriate single measurement of Christmas tree water status and a suitable index of the damage threshold.