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The Chemistry of WineFrom Blossom to Beverage and Beyond$
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David R. Dalton

Print publication date: 2018

Print ISBN-13: 9780190687199

Published to Oxford Scholarship Online: November 2020

DOI: 10.1093/oso/9780190687199.001.0001

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PRINTED FROM OXFORD SCHOLARSHIP ONLINE (oxford.universitypressscholarship.com). (c) Copyright Oxford University Press, 2021. All Rights Reserved. An individual user may print out a PDF of a single chapter of a monograph in OSO for personal use. date: 05 March 2021

The Light on the Leaves

The Light on the Leaves

Chapter:
9 The Light on the Leaves
Source:
The Chemistry of Wine
Author(s):

David R. Dalton

Publisher:
Oxford University Press
DOI:10.1093/oso/9780190687199.003.0017

As noted earlier in the general description of the plant cell, there is a site at which photosynthesis, the process which allows plants to capture sunlight and convert it into energy, occurs. It is this process which has produced oxygen on the planet, food for herbivores, and the cool green hills of Earth we enjoy today. The capture of sunlight allows the grape vine to grow and produce fruit. Of course, while the discussion of the “light reactions” (capture of sunlight) and the subsequent so-called “dark reactions” (producing carbohydrates) is necessarily brief here, it is, nonetheless, an exciting story. We are only now beginning to understand a little of it. The earlier picture (Figure 7.1) of the plant cell is repeated here (Figure 9.1) so that the position of the chloroplast is seen. Refer to page 24 for a discussion of the numbered items. As the leaves begin to develop alongside the apical meristem, proplastids, which are present in the meristematic regions of the plant, are formed. Proplastids grow into plas¬tids (such as amyloplasts and chloroplasts) as they mature in different ways dictated by the plant’s DNA. Some plastids (e.g., chloroplasts) carry pigments, discussed more fully below, that allow them to carry out photosynthesis. Others are used for storage of fat, starch (amyloplasts) or specialized proteins. Still other plastids are used to synthesize specialized compounds needed to form different tissues or to produce compounds for protection (e.g., tannins). Each plastid builds multiple copies of its DNA as it grows. If it is growing rapidly, it makes more genome copies than if it is growing slowly. The genes, ignoring epigenetic (literally “above the gene”) and postgenetic (literally “after the gene”) modifications, about which we still have much to learn, encode plastid proteins, the regulation of whose expression controls differentiation and thus which plastid is eventually formed. However, despite the differentiation of plastids, it appears that many plastids remain connected to each other by tubes called stromules through which proteins can be exchanged.

Keywords:   amyloplasts, carbohydrates, dark reactions, epigenetic, generic plant cell, light reactions, membranes, of chloroplast, nucleoids, phosphatidylcholine, ribosomes

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