Physiological Changes In Asparagus Spears Immediately After Harvest

Scientia Horticulturae, 4 4 ( 1990 ) 191-199

191

E lsevier Science Publishers B.V., A m s t e r d a m

P hysiological changes in asparagus spears
i mmediately after harvest
R .E. Lill, G.A. King and E.M. O'Donoghue
Horticultural Research Centre, MAFTech, Ministry ofAgriculture and Fisheries, PrivateBag, Levin
(New Zealand)
( Accepted for publication 12 February 1990)

A BSTRACT
Lill, R.E., King, G.A. and O'Donoghue, E.M., 1990. Physiological changes in asparagus spears imm ediately after harvest. Scientia Hortic., 4 4:191-199.
R espiratory activity of asparagus spears measured in the field showed a 4-fold increase between the
b utt and the tip of 190-ram spears. After harvest, there was an immediate rise in the respiration rate,
f ollowed by a rapid drop during 24 h at16 ° C to a constant level, ~ 30% of the peak respiration rate.
S trong gradients of sugars and proteins were measured along the spears with low levels of sugars and
h igh levels of proteins present in the spear tips. Sugars declined markedly in the first 24 h after harv est, particularly in spear tips. Proteins in spear tips were unchanged 24 h after harvest, but had
d ecreased 25% by 72 h.Total free amino acids remained steady for the first 24 h after harvest, but
i ncreased by 75% at 48 h. Asparagine/aspartic acid increased, whereas glutamine/glutamic acid and
p roline decreased in concentration substantially during the first 24 h after harvest. Tips of taller spears
h ad a lower sugar content and more protein than tips of short spears.
K eywords: amino acids; Asparagusofficinalis L; protein; respiration; sugars.

INTRODUCTION

A sparagus spears are very active metabolically and highly perishable duri ng handling and storage (Lill, 1980; King et al., 1988 ). A shelf life of 4-5
d ays after storage for 3-4 weeks is desired by the New Zealand industry to
e nable sea freight of asparagus to Northern Hemisphere markets, but is not
y et reliably attainable due totissue deterioration during shelf life (Lill, 1980;
K ing et al., 1986, 1988 ). A more complete understanding of the deteriorative
p rocess is required before significant progress can be made in extending the
s helf life of asparagus after storage.
P erishability relates in part to the tissue type of the organ. In asparagus, the
p attern of deterioration is influenced by the heterogeneity of thetissues: the
t ip comprises actively dividing meristematic cells grading into a zone of cell ular elongation, whereas the butt comprises more mature tissue where cell
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R.E. LILL ET AL.

e longation has ceased and the vascular tissue is lignifying. Highly metabolic
t issues generally have poor storage potential(Burton, 1982).
T issue heterogeneity is reflected in physiological gradients in the spear. Tip
s ections of detached spears produce CO2 at four times the rate of butt sections
1 d ay after harvest (Saltveit and Kasmire, 1985 ). Tips have high concentrat ions of total nitrogen (Culpepper and Moon, 1939), protein (Hsaio et al.,
1981; Saltveit and Kasmire, 1985; King et al., 1988 ), free aminoacids ( Saltv eit and Kasmire, 1985 ) and dry matter (Culpepper and Moon, 1939; Scott
a nd Kramer, 1949), but are low in soluble carbohydrate (Culpepper and
M oon, 1939; Hsaio et al., 1981; King et al., 1988) in comparison with the
b utt.
S ome of these gradients appear to change as the spear grows. Culpepper and
M oon (1939) report that total sugars in the tip of 200-mm spears are onet enth thelevel in the tip of 100-mm spears, whereas levels in the butt are
s imilar in both heights of spear. Nitrogen levels appear to be closely related
t o the zone of elongation, with levels increasing rapidly above this zone tow ard the tip (Culpepper and Moon, 1939). The nitrogen concentrations in
t he tip do not alter in taller spears, but because the amount of fully elongated
t issue...