Plant physiology

About: Plant physiology is a research topic. Over the lifetime, 1537 publications have been published within this topic receiving 72038 citations.

Role of Abscisic Acid in Seed Dormancy

Abstract: Seed dormancy is an adaptive trait that improves survival of the next generation by optimizing the distribution of germination over time. The agricultural and forest industries rely on seeds that exhibit high rates of germination and vigorous, synchronous growth after germination; hence dormancy is sometimes considered an undesirable trait. The forest industry encounters problems with the pronounced dormancy of some conifer seeds, a feature that can lead to non-uniform germination and poor seedling vigor. In cereal crops, an optimum balance is most sought after; some dormancy at harvest is favored because it prevents germination of the physiologically mature grain in the head prior to harvest (that is, preharvest sprouting), a phenomenon that leads to considerable damage to grain quality and is especially prominent in cool moist environments. The sesquiterpene abscisic acid (ABA) regulates key events during seed formation, such as the deposition of storage reserves, prevention of precocious germination, acquisition of desiccation tolerance, and induction of primary dormancy. Its regulatory role is achieved in part by cross-talk with other hormones and their associated signaling networks, via mechanisms that are largely unknown. Quantitative genetics and functional genomics approaches will contribute to the elucidation of genes and proteins that control seed dormancy and germination, including components of the ABA signal transduction pathway. Dynamic changes in ABA biosynthesis and catabolism elicit hormone-signaling changes that affect downstream gene expression and thereby regulate critical checkpoints at the transitions from dormancy to germination and from germination to growth. Some of the recent developments in these areas are discussed.

Elevated atmospheric partial pressure of CO2 and plant growth. II. Non-structural carbohydrate content in cotton plants and its effect on growth parameters.

Abstract: Cotton plants were grown in late spring under full sunlight in glasshouses containing normal ambient partial pressure of CO2 (32±2Pa) and enriched partial pressure of CO2 (64±1.5Pa) and at four levels of nitrogen nutrition. Thirty-five days after planting, the total dry weights of high CO2-grown plants were 2- to 3.5-fold greater than plants grown in normal ambient CO2 partial pressure. Depending on nitrogen nutrition level, non-structural carbohydrate content (mainly starch) in the leaves of plants grown in normal CO2 was between 4 and 37% of the total leaf dry weight compared to 39 to 52% in the leaves of high CO2-grown plants. Specific leaf weight calculated using total dry weight was 1.6- to 2-fold greater than that based on structural dry weight. In high CO2-grown plants the amount of non-structural carbohydrate translocated from the leaves at night was between 10 and 20% of the level at the end of the photoperiod. This suggests that the plant was unable to utilize all the carbohydrate it assimilated in elevated CO2 atmosphere. While there was a 1.5-fold enhancement in the rate of CO2 assimilation in plants grown in 64 Pa CO2, there was, however, some evidence to suggest that the activities of other metabolic pathways in the plants were not stimulated to the same extent by the enriched CO2 atmosphere. This resulted in massive accumulation of non-structural carbohydrate, particularly at low level of nitrogen nutrition.

Responses of individual plants to harvesting

Abstract: Introduct ion ................................................................................................................................................................ 533 Compar ison of Cl ipping to G r a z i n g .............................................................................................. 533 Effect of Herbage Removal on Above-Ground Par ts of P lants ........................ 533 Dry Mat te r Yield ............................................................................................................................... 533 Grasses ........................................................................................................................................... 533 Forbs ...................................................................................................................................................... 537 Grass -Legume Mixtures ...................................................................................................... 537 Shrubs ..................................................................................................................................................... 538 Relat ionship of Dry Mat ter Yield to Physiological Processes .................. 539 Competit ion for Light and Carbon Diox ide the Leaf Area Index .................................................................................................... 539 Apical Dominance and Growth of Lateral Buds ......................................... 541 P lan t Form ........................................................................................................................................................ 547 Protein Yield ................................................................................................................................................ 547 Seed Product ion ......................................................................................................................................... 550 Genera l .................................................................................................................................................. 550 Relat ionship to Photoperiodism and Vernal izat ion ................................... 554 Effect of Herbage Removal on Root Growth and Root Weigh t s ..................... 555 Effect of Root Removal on T op Growth ..................................................................................... 557 Relat ionship of Season and Fru i t ing to Carbohydrate Storage .......................... 558 T r e n d s in Herbaceous Plants ....................................................................................................... 558 T r e n d s in Woody Plants ................................................................................................................ 559 Mechan i sms and Variat ions ............................................................................................................ 560 Effects of Herbage Removal on Chemical Relat ionships of Roots .................. 562 Chemical Benefits of G r a z i n g An ima l s to Herbage Plants ...................................... 571 Conclusions ................................................................................................................................................................... 571 Li terature Cited .................................................................................................................................................. 573

Seed dormancy and germination: the role of abscisic acid and gibberellins and the importance of hormone mutants

Abstract: Over the past decades many studies have aimed at elucidating the regulation of seed dormancy and germination. Many hypotheses have been proposed and rejected but the regulatory principle behind changes in dormancy and induction of germination is still a ‘black’ box. The majority of proposed mechanisms have a role for certain plant hormones in common. Abscisic acid and the gibberellins are the hormones most frequently suggested to control these processes. The development of hormone-deficient mutants made it possible to provide direct evidence for the involvement of hormones in germination and dormancy related processes. In the present paper an attempt is made to assess the role of abscisic acid and gibberellins in the transitions between dormant and non-dormant states and germination. First a conceptual framework is presented in which the different states of dormancy and germination are defined in order to contribute to a solution of the semantic confusion about these terms that has existed since the beginning of seed physiology. It is concluded that abscisic acid plays a pivotal role during the development of primary dormancy and gibberellins are involved in the induction of germination. Changes in sensitivity to these hormones occur during changes in dormancy. Both synthesis of and responsiveness to the hormones are controlled by natural environmental factors such as light, temperature and nitrate.

The function of calcium in plants

Abstract: Introduction ................................................................................................................................................................................................ 407 The calcium requirement of plants ................................................................................................................................ 408 Anatomical and cytological effects of calcium deficiency ........................................................................ 410 Gross defects ................................................................................................................................................................................... 410 Cellular and subeellular effects ...................................................................................................................................... 411 Physiological and biochemical evidence for the role of calcium ................................................. 412 Cell wall ................................................................................................................................................................................................. 412 Ion absorption and membranes ...................................................................................................................................... 414 Ion absorption by whole cells ...................................................................................................................................... 414 Mitoehondria ............................................................................................................................................................................... 416 Membranes and model systems ................................................................................................................................ 417 Nucleic acids and chromosomes ...................................................................................................................................... 418 Enzyme activity .............................................................................................................................................................................. 418 Concluding discussion .................................................................................................................................................................... 420 Literature cited ....................................................................................................................................................................................... 421