cladophyll

The values of A measured in senescent cladophyll tissue in April were characterized by a significant decline in both cultivars, although PFDs were still above those capable of saturating photosynthesis.

In the rapidly expanding cladophyll tissue (January), values of [g.sub.s] were similar for the two cultivars.

A/[C.sub.i] and A/PFD Responses and Cladophyll Fluorescence Characteristics

Cladophyll diameter in ASP-69 was significantly greater than in ASP-03 (Table 3).

In addition, the high-yielding cultivar ASP-69 displays significantly greater [V.sub.cmax], [g.sub.s], SLW, and cladophyll diameter in comparison with the low-yielding cultivar ASP03.

For the cultivars examined in our study, [A.sub.sat] increased with both cladophyll diameter and the ratio of cladophyll volume/area.

First, increasing cladophyll diameter increased the concentration of photosynthetic apparatus per unit of cladophyll surface area.

Observations of cladophyll anatomy revealed that cultivar variation in cladophyll diameter resulted from variation in the thickness of the palisade mesophyll layer (number of cells), not differences in cell size or shape, or the size of the internal air space (Faville, 1997).

Differences in photosynthetic capacity were related to cladophyll diameter.

In asparagus, photosynthesis occurs in small cladophylls (Downton and Torokfalvy, 1975) which constitute the bulk of the foliar portion of the plant, commonly called the fern.