Physiologia Plantarum
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Hormonal regulation of α‐amylase gene expression in germinating wheat (<i>Triticum aestivum</i>) grains The diffusion of GA1 and GA3 from the embryo, and the decline in ABA content of endosperm, were associated with the induction of α‐amylase (EC 3.2.1.1) gene expression in aleurone of intact wheat (Triticum aestivum L. cv. Maris Huntsman) grains germinated at 25°C. The scutellum appeared to be the main site of de novo GA biosynthesis based on (1) the abundance of transcripts of a cloned wheat GA 20‐oxidase. (2) the increase in content of GAs belonging to the early 13‐hydroxylation GA pathway, and (3) the accumulation of ent ‐kaurene in grains imbibed in the presence of an ent ‐kaurene oxidase inhibitor. Again, the initiation of GA biosynthesis in the scutellum was closely associated with the induction of α‐amylase gene expression in scutellar epithelium, although the two events may not have been causally linked. The embryo was required to be present for 36 h from the start of imbibition in order to induce α‐amylase activity in aleurone, and the response could be replicated by low doses of GA1 applied to de‐embryonated grains. After‐ripened wheat aleurone was relatively unresponsive to applied ABA in terms of suppression of GA‐induced α‐amylase production. Subtle differences were observed in the temporal pattern of α‐amylase gene expression between intact germinated grains and de‐embryonated grains challenged with GA1 . It appears that endogenous GAs are an important component of the embryo stimulus initiating α‐amylase gene expression in aleurone of germinating wheat grain, as originally proposed for barley. Their role in the synthesis of α‐amylase in scutellar epithelium remains to be clarified.
Physiologia Plantarum - Tập 100 Số 3 - Trang 534-542 - 1997
The effects of low water contents on physiological activities of seeds Physiological activity changes in seeds when water content is changed from 0 to 40%. The limited metabolism of dry seeds allows for studies of the role of water in the biochemical reactions of living systems. At very low water contents, seeds exhibit limited biochemical activity, however light reactions and some oxidative processes are possible. As water content is increased, enzymatic reactions are increasingly facilitated. At moisture contents of about 24% mitochondrial electron transport is detectable. Changes in the physiological activity of seeds occur at discrete moisture levels that are reflective of discrete changes in the thermodynamic properties of water.
Physiologia Plantarum - Tập 77 Số 1 - Trang 172-176 - 1989
Nitrogen Stress in Birch Seedlings Abstract An account is given of experiments with birch (Betula verrucosa Ehrh.), in which experiments there was optimum availability of all other nutrients, while nitrogen was added in amounts corresponding to optimum as well as various non‐optimum consumption rates. At the beginning of the growth period the nitrogen concentration in the nutrient solutions was very low or zero in the sub optimum treatments. In the optimum and supra–optimum treatments the nitrogen concentration in the solution was varied up to high levels. The nutrient solutions were not changed but the nutrients taken up were replaced by frequent additions. The sub‐optimum nitrogen additions were carried out every second hour in amounts increasing exponentially day by day, and with a varied exponent. During a lag phase the seedlings in the sub optimum treatments had rapidly diminishing growth rates, deficiency symptoms, and a relatively high root growth rate with formation of long, thin roots. When the growth rate later on had stabilized, a period was recognized during which measurements and sampling were carried out. At the end of the lag phase, or in the beginning of the experimental period, the nitrogen deficiency symptoms of the leaves disappeared and the various parts of the seedlings grew with the same rate, and in a good linear correlation with the rate of nitrogen supply. The results indicate that nitrogen primarily influences the leaf area growth rate, which responds rapidly to a change in nitrogen availability. The following general growth response demonstrates the ability of the plants to adapt growth according to nitrogen supply, so as to create stable internal physiological conditions. Thus, there is a close agreement between the rate of nitrogen supply and consumption on one hand and growth rate on the other. The characteristic nitrogen deficiency symptoms of the seedlings during the lag phase are very similar to those reported in the literature. During the stable period that follows, they disappear from the leaves in agreement with the fact that natural vegetation generally is green also when nitrogen is strongly growth limiting. It is concluded that the exponentially increasing amounts of nitrogen added to lie nutrient solution, also when the exponent is far below optimum, makes nitrogen available to the seedlings in a similar way as does the exponentially growing root system in. a solid medium. Birch seedlings are able to adapt growth rate to low nitrogen supply and thereby show a healthy appearance without acute deficiency symptoms. Some ecological and practical implications are discussed.
Physiologia Plantarum - Tập 45 Số 1 - Trang 137-148 - 1979
Boric acid and salinity effects on maize roots. Response of aquaporins ZmPIP1 and ZmPIP2, and plasma membrane H<sup>+</sup>‐ATPase, in relation to water and nutrient uptake Under saline conditions, an optimal cell water balance, possibly mediated by aquaporins, is important to maintain the whole‐plant water status. Furthermore, excessive accumulation of boric acid in the soil solution can be observed in saline soils. In this work, the interaction between salinity and excess boron with respect to the root hydraulic conductance (L0 ), abundance of aquaporins (ZmPIP1 and ZmPIP2), ATPase activity and root sap nutrient content, in the highly boron‐ and salt‐tolerant Zea mays L. cv. amylacea, was evaluated. A downregulation of root ZmPIP1 and ZmPIP2 aquaporin contents were observed in NaCl‐treated plants in agreement with the L0 measurements. However, in the H3 BO3 ‐treated plants differences in the ZmPIP1 and ZmPIP2 abundance were observed. The ATPase activity was related directly to the amount of ATPase protein and Na+ concentration in the roots, for which an increase in NaCl‐ and H3 BO3 + NaCl‐treated plants was observed with respect to untreated and H3 BO3 ‐treated plants. Although nutrient imbalance may result from the effect of salinity or H3 BO3 alone, an ameliorative effect was observed when both treatments were applied together. In conclusion, our results suggest that under salt stress, the activity of specific membrane components can be influenced directly by boric acid, regulating the functions of certain aquaporin isoforms and ATPase as possible components of the salinity tolerance mechanism.
Physiologia Plantarum - Tập 132 Số 4 - Trang 479-490 - 2008
Co‐regulation of water channels and potassium channels in rice Aquaporins and potassium channel proteins are probably critical for a plant to maintain proper cytosolic osmolarity in response to drought or other stresses. However, evidence linking water channel and potassium channel functions in plants remains to be demonstrated. The present study examined K+ channel/transporters and water channels in rice (Oryza sativa L. spp. indica cv. Guangluai 4) to reveal a potential functional correlation. The mRNA expression levels of plasma membrane intrinsic proteins (PIPs) and K+ channel/transporters responded similarly to K+ starvation or water deprivation. Transcription of the PIP‐ and K+ channel‐encoding genes was induced by K+ starvation and could be downregulated by polyethylene glycol (PEG)‐mediated water deficit. Consistent with the induced PIP expression, root hydraulic conductivity (Lp ) also increased during K+ starvation. Furthermore, the K+ uptake capacity, but not the K+ content, was probably influenced by K+ starvation. Caesium chloride treatment decreased K+ content in the rice seedlings and reduced root Lp as did mercuric chloride. These results are compatible with the conclusion that PIP and K+ channel/transporters are functionally co‐regulated in rice osmoregulation.
Physiologia Plantarum - Tập 128 Số 1 - Trang 58-69 - 2006
Ultrastructure of the cuticle during growth of the grape berry (<i>Vitis vinifera</i> L.) The outer surface morphology and the ultrastructure of grape berries during growth were examined by electron microscopy. The cuticle began to form before anthesis as highly organized and tightly appressed cuticular ridges. During the period of rapid expansion, the cuticular material spread out over the grape berry. At the same time, an outer wax layer of about 0.5 μm was indentified. As growth proceeded, the cuticular material flattened out and eventually disappeared. At the final stage of growth, the berry had a smooth, continuous and homogeneous cuticle with a thickness of 3 μm.
Physiologia Plantarum - Tập 111 Số 2 - Trang 220-224 - 2001
Changes in jasmonic acid concentration during early development of apple fruit Apple fruits (Malus domestica Borkh.) were harvested from 24 to 136 days after full bloom (DAFB) and endogenous jasmonic acid was analyzed by GC‐MS. There were two isomers of jasmonic acid in apple fruit with a ratio of 37:63 (cis:trans ). The cis:trans ratio remained relatively constant throughout this period of fruit development. The endogenous jasmonic acid concentration was 138 ng g−1 fresh weight 24 DAFB and decreased as fruit developed. Changes in jasmonic acid concentration were coincident with those of respiration, ethylene production, and anthocyanin accumulation in patterns consistent with the reported responses to exogenous jasmonates. Possible roles for jasmonic acid during early fruit development are discussed.
Physiologia Plantarum - Tập 101 Số 2 - Trang 328-332 - 1997
Effect of brassinolide, alone and in concert with abscisic acid, on control of stomatal aperture and potassium currents of <i>Vicia faba</i> guard cell protoplasts The essential role of brassinosteroids (BRs) in normal plant growth, development and physiology has been established by the analysis of biosynthesis and signal transduction mutants. Some of the BR‐related mutants also display altered sensitivity to the phytohormone abscisic acid (ABA) suggesting that BRs normally counteract the effects of ABA on root growth, seed germination, and possibly stomatal movement. In this study, the effect of a specific BR, brassinolide (BL), on guard cell function of Vicia faba was examined alone and in conjunction with ABA. Unlike other described plant responses, BL did not oppose the effect of ABA in regulation of stomatal movement. On the contrary, BL modulated stomatal aperture by promoting stomatal closure and inhibiting stomatal opening, functions of this hormone that were previously undescribed. This study also demonstrated a role for plant steroidal hormones in ion channel regulation: BL inhibited inwardly rectifying K+ currents of V. faba guard cell protoplasts in a manner similar to ABA. In both stomatal movement assays and whole‐cell patch clamp experiments, the effects of BL and ABA applied together were not additive, suggesting that these two hormones may function in interacting pathways to regulate stomatal apertures and guard cell physiology.
Physiologia Plantarum - Tập 128 Số 1 - Trang 134-143 - 2006
Effects of NaCl on responses of ectomycorrhizal black spruce (<i>Picea mariana</i>), white spruce (<i>Picea glauca</i>) and jack pine (<i>Pinus banksiana</i>) to fluoride Black spruce (Picea mariana ), white spruce (Picea glauca ) and jack pine (Pinus banksiana ) were inoculated with Suillus tomentosus and subjected to potassium fluoride (1 mM KF and 5 mM KF) in the presence and absence of 60 mM NaCl. The NaCl and KF treatments reduced total dry weights in jack pine and black spruce seedlings, but they did not affect total dry weights in white spruce seedlings. The addition of 60 mM NaCl to KF treatment solutions alleviated fluoride‐induced needle injury in ectomycorrhizal (ECM) black spruce and white spruce, but had little effect in jack pine seedlings. Both KF and 60 mM NaCl treatments reduced E values compared with non‐treated control seedlings. However, with the exception of small reductions of Kr by NaCl treatments in black spruce, the applied KF and NaCl treatments had little effect on Kr in ECM plants. Chloride tissue concentrations in NaCl‐treated plants were not affected by the presence of KF in treatment solutions. However, shoot F concentrations in ECM black spruce and white spruce treated with 5 mM KF + 60 mM NaCl were significantly reduced compared with the 5 mM KF treatment. The results point to a possible competitive inhibition of F transport by Cl. We also suggest that the possibility that aquaporins may be involved in the transmembrane transport of F should be further investigated.
Physiologia Plantarum - Tập 135 Số 1 - Trang 51-61 - 2009
Ion uptake in <i>Pinus banksiana</i> treated with sodium chloride and sodium sulphate Within its wide range across Canada, jack pine is exposed to salinity from both natural and anthropogenic sources. To compare the effects of Cl and SO4 on salt injury, sand and solution‐culture grown jack pine (Pinus banksiana Lamb.) seedlings were treated with nutrient solutions containing 60 or 120 mM NaCl, 60 mM Na2 SO4 , or a mixture of 60 mM NaCl and 30 mM Na2 SO4 . After 5 weeks of salt treatments, concentrations of Cl, K, Na, and SO4 were determined in roots, stem and needles of the current and previous years growth, and in necrotic needles. To determine the role of water uptake in the absorption and translocation of salts in plants, total transpiration was measured as the loss of water from a sealed system and related to total plant uptake of Cl, Na, and SO4 . Sodium uptake and root‐to‐shoot transport rates were greater in treatments containing Cl. A delay in root‐to‐shoot transport of both Na and Cl indicates retention of these ions in the roots. Electrolyte leakage of needles was more closely related to treatment Cl concentrations than treatment Na concentrations. The transport of Na ions to the shoot was related to the presence of Cl, but was not related to transpiration rate.
Physiologia Plantarum - Tập 120 Số 3 - Trang 482-490 - 2004
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