Abstract
Haber, Alan H., and D. E. Foard. (Oak Ridge Natl. Lab., Oak Ridge, Tenn.) Nonessentiality of concurrent cell divisions for degree of polarization of leaf growth. II. Evidence from untreated plants and from chemically induced changes of the degree of polarization. Amer. Jour. Bot. 50(9): 937–944. Illus. 1963.—Tobacco leaves grow with a constant degree of polarization (i.e., ratio of rate of increase in length per mm length to rate of increase in width per mm width). During this growth there is decreasing mitotic activity. Data from the literature, including Sinnott's classic studies with cucurbit fruits, provide additional specific examples of growth of (1) constant degree of polarization during which (2) mitotic activity falls. The generalization that cell division plays no role in maintaining a constant degree of polarization is suggested by the widespread occurrence of these 2 features of growth in determinate organs. These considerations are consistent with our earlier finding that the degree of polarization of growth of the first foliage leaf of wheat is the same in seedlings normally growing with oriented cell divisions and in gamma‐plantlets, which are seedlings growing without cell division owing to gamma‐irradiation of the grain before sowing. The present work shows that the degree of polarization can be significantly increased by treatment with gibberellic acid and decreased by colchicine, even though it is unaffected by radiation‐induced mitotic inhibition. These chemically induced changes in the degree of polarization are, moreover, the same in unirradiated and in gamma‐plantlet leaves. We conclude that cell division is essential neither for maintaining the degree of polarization nor for changing the degree of polarization. These considerations lead to 3 biological conclusions, each of which is in harmony with simple geometric considerations: (1) cell divisions do not directly contribute to or cause growth; (2) cell division plays an essential and immediate role in influencing cell forms, but plays a secondary and much less important role in influencing organ form; and (3) there is a fallacy in the usual and accepted manner of interpreting changes in organ size as being due to changes in cell size and changes in cell number.
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Claims 10
Claim · model-written summary
Tobacco leaves maintain constant growth polarization while mitotic activity declines.
- Taxon
- Tobacco
Nicotiana tabacume0 - Organ / stage
- leavese0
- Outcome
- constant degree of polarizatione0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Tobacco leaves grow with a constant degree of polarization (i.e., ratio of rate of increase in length per mm length to rate of increase in width per mm width). During this growth there is decreasing mitotic activity”
Claim · model-written summary
Wheat leaf polarization was the same in normal seedlings and gamma-plantlets.
- Taxon
- wheat
Triticum aestivume0 - Organ / stage
- first foliage leafe0
- Treatment
- gamma‐plantletse0
- Outcome
- degree of polarization of growthe0
- Direction
- the samee0
- Comparator
- seedlings normally growing with oriented cell divisionse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“the degree of polarization of growth of the first foliage leaf of wheat is the same in seedlings normally growing with oriented cell divisions and in gamma‐plantlets”
Claim · model-written summary
Gibberellic acid significantly increased polarization.
Not reportedTaxonComparator
Verbatim
e0“the degree of polarization can be significantly increased by treatment with gibberellic acid”
Claim · model-written summary
Colchicine decreased polarization.
Not reportedTaxonComparator
Verbatim
e0“the degree of polarization can be significantly increased by treatment with gibberellic acid and decreased by colchicine”
Claim · model-written summary
Radiation-induced mitotic inhibition left polarization unaffected.
Not reportedTaxonComparator
Verbatim
e0“it is unaffected by radiation‐induced mitotic inhibition”
Claim · model-written summary
Chemical changes in polarization were the same in unirradiated and gamma-plantlet leaves.
- Outcome
- degree of polarizatione0
- Direction
- the samee0
- Comparator
- unirradiated and in gamma‐plantlet leavese0
Not reportedTaxon
Verbatim
e0“These chemically induced changes in the degree of polarization are, moreover, the same in unirradiated and in gamma‐plantlet leaves”
Claim · model-written summary
Authors concluded cell division is unnecessary for maintaining or changing polarization.
Not reportedTaxon
Verbatim
e0“cell division is essential neither for maintaining the degree of polarization nor for changing the degree of polarization”
Claim · model-written summary
Authors inferred cell divisions do not directly cause growth.
Not reportedTaxon
Verbatim
e0“cell divisions do not directly contribute to or cause growth”
Claim · model-written summary
Authors inferred division strongly affects cell form but less strongly affects organ form.
Not reportedTaxon
Verbatim
e0“cell division plays an essential and immediate role in influencing cell forms, but plays a secondary and much less important role in influencing organ form”
Claim · model-written summary
Authors challenged interpreting organ size through cell size and number.
Not reportedTaxon
Verbatim
e0“there is a fallacy in the usual and accepted manner of interpreting changes in organ size as being due to changes in cell size and changes in cell number”
The same questions in other papers
radiation · growth · Triticum aestivum (wheat)Positive and negative results
53 papers in the same direction as this paper · 35 reporting no difference from an alternative
- no effect
- negative
- positive
85 papers more in this group
See all 89 papers →Claims are grouped by organism, treatment and what was measured or targeted. A paper counts as positive when any of its claims in the group is positive.