Cucumber seedling dependence on cotyledonary leaves for early growth

Dilson Antônio Bisognin,Luis Velasquez,Irvin Widders

doi:10.1590/s0100-204x2005000600002

Dilson Antônio Bisognin, Luis Velasquez + Show 1 more

Open Access

https://doi.org/10.1590/s0100-204x2005000600002

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Abstract

The objective of this work was to evaluate the dependence of cucumber (Cucumis sativus L.) seedlings on cotyledonary leaves for early growth and establishment. Sets of two uniform emerging seedlings were used to quantify the initial growth and dry matter accumulation, as well as the intensity and stage of cotyledon damage in seedling establishment and to determine cotyledon protein, amino acid and carbohydrate contributions to the growing seedling. Cucumber seedling establishment was found to be highly dependent on cotyledonary leaves. Root system establishment was highly dependent on the health of the aerial part. One cotyledon was enough to maintain aerial growth of seedlings after unfolding the first true leaf. Cucumber seedlings depended on both cotyledons to keep root system growth at least until leaf area was equivalent to cotyledon area. Covering one or both cotyledons of seedlings with one unfolded leaf increased carbohydrate content of uncovered cotyledon and leaves compared with control seedlings. Cucumber seedlings are highly dependent on cotyledonary leaves and aerial parts are less dependent than root system. Cotyledon damage at early stages of plant establishment would adversely impact crop yield by reducing plant density, an important yield component, or slowing down seedling growth and establishment.

Highlights

Cucumber (Cucumis sativus L.) has epigeal emergence, in which the hypocotyl pulls the cotyledons out of the soil after the initial development of primary and secondary roots (Nelson & Larson, 1984)
Cotyledonary leaf area and dry matter accumulations of cucumber seedlings followed a time course trend that could be characterized by a non-linear sigmoid model (Figure 1)
True leaf area reached the equivalence with cotyledonary area at 12.4 days after emergence (DAE)

Summary

Introduction

Cucumber (Cucumis sativus L.) has epigeal emergence, in which the hypocotyl pulls the cotyledons out of the soil after the initial development of primary and secondary roots (Nelson & Larson, 1984). Cucumber cotyledons undergo a high rate of expansion growth after emergence, resulting from increases in cell size and number. A high rate of cotyledon expansion associated with chlorophyll production and presence of functional stomata made cucumber cotyledons adapted for photosynthesis (Lovell & Moore, 1970). Cucumber seedling depends on seed reserves only during the preemergence growth.

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