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Shoot

About: Shoot is a research topic. Over the lifetime, 32188 publications have been published within this topic receiving 693348 citations.


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Journal ArticleDOI
TL;DR: It is proposed that a greater proportion of nitrate assimilation occurs in the shoot when an increase in the rate of nitrates uptake does not induce an increaseIn NR level in the root, and a greaterportion of the nitrate taken up remains unassimilated and is passed into the xylem.
Abstract: The partitioning of nitrate assimilation between root and shoot of higher plant species is indicated by the relative proportions of total plant nitrate reductase activity (NRA) in the two plant parts and the relative concentrations of nitrate and reduced N in the xylem sap. These have been collated here from the literature and temperate and tropical species compared. Both the distribution of NRA and xylem sap nitrate: reduced N indicate that the following four generalizations can be made. 1Temperate, perennial species growing in low external nitrate concentrations (about 1 mol m−3) carry out most of their nitrate assimilation in the root. As external nitrate concentration increases (in the range found in agricultural soils, 1–20 mol m−3), shoot nitrate assimilation becomes increasingly important. 2Temperate, annual legume species growing in low external nitrate concentrations carry out most of their nitrate assimilation in the root. Shoot nitrate assimilation increases in importance as external nitrate concentration is increased. 3Temperate, annual non-legume species vary greatly in their partitioning of nitrate assimilation between root and shoot when growing in low external nitrate concentrations. Regardless of the proportion carried out in the root at low external nitrate concentrations, nitrate assimilation in the shoot becomes increasingly important as external nitrate concentration is increased. 4Tropical and subtropical species, annual and perennial, carry out a substantial proportion of their nitrate assimilation in the shoot when growing in low external nitrate concentrations. The partitioning of nitrate assimilation between root and shoot remains constant as external nitrate concentration increases. It is proposed that a greater proportion of nitrate assimilation occurs in the shoot when an increase in the rate of nitrate uptake does not induce an increase in NR level in the root. Thus, a greater proportion of the nitrate taken up remains unassimilated and is passed into the xylem. A constant partitioning of nitrate assimilation between root and shoot is achieved by balancing NR levels in the root with rates of nitrate uptake. The advantages and disadvantages of assimilating nitrate in either the root or shoot are discussed in relation to temperate and tropical habitats.

464 citations

Journal ArticleDOI
TL;DR: The question of whether abscisic acid acts as an inhibitor or promoter of shoot growth in plants growing in drying soil is examined, drawing on current understanding of the role of ABA in root growth maintenance.
Abstract: The question of whether abscisic acid (ABA) acts as an inhibitor or promoter of shoot growth in plants growing in drying soil is examined, drawing on current understanding of the role of ABA in root growth maintenance. Particular consideration is given to studies of endogenous ABA deficiency, which have shown that an important role of ABA is to limit ethylene production, and that this interaction is involved in the effects of ABA status on shoot and root growth.

460 citations

Book ChapterDOI
01 Jan 1965
TL;DR: The central problem of the physiology of flower initiation is to understand which factors cause a shoot meristem to become a flower primordium, and how they consummate their action.
Abstract: Flower initiation marks the transition from vegetative to reproductive growth in seed plants. It is thus a crucial event in the life of these plants, particularly so because of the peculiar relation of vegetative and reproductive development in seed plants which is in turn an outcome of the morphological nature of the flower. Flowers are modified shoots which are produced by modified shoot meristems, the flower primordia. However, once a meristem has been determined as a flower primordium, it is usually unable — except perhaps at the very earliest stages — of reverting to vegetative growth. Vegetative growth and reproductive development in seed plants are thus in a certain sense mutually exclusive; as far as a particular meristem is concerned, flower initiation means the end of its life. The central problem of the physiology of flower initiation is to understand which factors cause a shoot meristem to become a flower primordium, and how they consummate their action.

455 citations

Journal ArticleDOI
01 Oct 1979-Planta
TL;DR: Potted maize seedlings were subjected to a single period of water stress and a significant accumulation of solutes in the root tips of the unwatered plants resulted in the maintenance of root turgor for the duration of the water stress treatment.
Abstract: Potted maize seedlings were subjected to a single period of water stress. As the severity of water stress increased, measurements were made of leaf and root solute and water potentials, leaf diffusive conductance and leaf and root growth. After day four of the drying cycle, the rate of leaf extension and the development of leaf area were reduced. This reduction correlated well with a reduction in leaf turgor which occurred at this time. A significant accumulation of solutes in the root tips of the unwatered plants resulted in the maintenance of root turgor for the duration of the water stress treatment. Root growth of the unwatered plants was also maintained as the severity of water stress increased. A mild degree of water stress resulted in a net increase in root growth compared to the situation in well-watered plants. The significance of solute regulation and continued root growth for plants growing in drying soil is discussed.

455 citations

Journal ArticleDOI
TL;DR: Thirty diverse genotypes of bread wheat were evaluated for seed vigour index, germination percentage, root length, shoot length, root-to-shoot length ratio, coleoptile length and osmotic membrane stability under laboratory conditions, indicating suppression of variability under moisture stress conditions.
Abstract: Thirty diverse genotypes of bread wheat were evaluated for seed vigour index, germination percentage, root length, shoot length, root-to-shoot length ratio, coleoptile length and osmotic membrane stability under laboratory conditions. Considerable variation was observed for all the characters. Discrimination among the genotypes on the basis of mean values was better under normal than under moisture stress conditions, indicating suppression of variability under moisture stress conditions. Comparison of mean performance under normal and osmotic stress conditions indicated that the seed vigour index was the most sensitive trait, followed by shoot length, germination percentage and root length. The root-to-shoot length ratio, however, increased under osmotic stress. The magnitude of genetic components of variance and heritability were, in general, lower under osmotic stress than under normal conditions. All the characters except germination percentage, shoot length and coleoptile length showed considerable genetic variability. Heritability in the broad sense was also moderate to high for all the characters under both environments. Due to high heritability and genetic advance great benefit from selection can be expected for the osmotic membrane stability of leaf segments and root-to-shoot length ratio. Moderate progress can be expected from root length and seed vigour index. Correlation studies indicated that the osmotic membrane stability of the leaf segment was the most important trait, followed by root-to-shoot ratio and root length on the basis of their relationships with other traits.

447 citations


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Performance
Metrics
No. of papers in the topic in previous years
YearPapers
20241
20232,131
20224,637
2021953
20201,041
20191,064